# Modules

Basic implementation of a module system including tests.

.gitea/workflows/test-and-build.yml

@@ -0,0 +1,65 @@
+name: Test, Build, and Release
+
+on: 
+  push:
+    tags:
+      - '*'
+
+jobs:
+  test:
+    container:
+      image: docker.matri.cx/nix-runner:v0.1.0
+      credentials:
+        username: ${{ secrets.REGISTRY_USERNAME }}
+        password: ${{ secrets.REGISTRY_PASSWORD }}
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Set up cache for Cabal
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cache/cabal
+            ~/.config/cabal
+            ~/.local/state/cabal
+          key: cabal-${{ hashFiles('tricu.cabal') }}
+          restore-keys: |
+            cabal-
+
+      - name: Initialize Cabal and update package list
+        run: |
+          nix develop --command cabal update
+
+      - name: Run test suite
+        run: |
+          nix develop --command cabal test
+
+  build:
+    needs: test
+    container:
+      image: docker.matri.cx/nix-runner:v0.1.0
+      credentials:
+        username: ${{ secrets.REGISTRY_USERNAME }}
+        password: ${{ secrets.REGISTRY_PASSWORD }}
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Build and shrink binary
+        run: |
+          nix build
+          cp -L ./result/bin/tricu ./tricu
+          chmod 755 ./tricu
+          nix develop --command upx ./tricu
+
+      - name: Release binary
+        uses: akkuman/gitea-release-action@v1
+        with:
+          files: |-
+            ./tricu
+          token: '${{ secrets.RELEASE_TOKEN }}'
+          body: '${{ gitea.event.head_commit.message }}'
+          prerelease: true

.gitignore

@@ -1,14 +1,11 @@
-bin/
-data/Purr.sqlite
-data/encryptionKey
-/result
-/config.dhall
-/Dockerfile
-/docker-stack.yml
-.stack-work/
 *.swp
-dist*
+*.txt
 *~
 .env
+.stack-work/
+/Dockerfile
+/config.dhall
+/result
 WD
-*.hs.txt
+bin/
+dist*

README.md

@@ -1,54 +1,89 @@
-# sapling
+# tricu
 
 ## Introduction
 
-sapling is a "micro-language" that I'm working on to investigate [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) .
+tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) terms, but minimal syntax sugar is included to provide a useful programming tool. tricu is under active development and you can expect breaking changes with nearly every commit.
 
-It offers a minimal amount of syntax sugar:
+tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
-- `t` operator behaving by the rules of Tree Calculus
-- Function ("variable") definitions
-- Lambda abstractions
-- List, Number, and String literals (WIP)
+## Features
 
-This is an active experimentation project by [someone who has no idea what they're doing](https://eversole.co).
+- Tree Calculus operator: `t`
+- Assignments: `x = t t`
+- Immutabile definitions
+- Lambda abstraction syntax: `id = (\a : a)`
+- List, Number, and String literals: `[(2) ("Hello")]` 
+- Function application: `not (not false)`
+- Higher order/first-class functions: `map (\a : lconcat a "!") [("Hello")]`
+- Intensionality blurs the distinction between functions and data (see REPL examples)
+- Simple module system for code organization
 
-## What does it look like?
+## REPL examples
 
 ```
-false      = t
-_          = t
-true       = t t
-id         = (\a : a)
-triage     = (\a b c : t (t a b) c) 
-match_bool = (\ot of : triage of (\_ : ot) t)
-and        = match_bool id (\_ : false)
-if         = (\cond then else : t (t else (t t then)) t cond)
-triage     = (\a b c : t (t a b) c)
-test       = triage "leaf" (\_ : "stem") (\_ _ : "fork")
+tricu < -- Anything after `--` on a single line is a comment
+tricu < id = (\a : a) -- Lambda abstraction is eliminated to tree calculus terms
+tricu < head (map (\i : lconcat i " world!") [("Hello, ")])
+tricu > "Hello,  world!"
+tricu < id (head (map (\i : lconcat i " world!") [("Hello, ")]))
+tricu > "Hello,  world!"
 
--- The REPL outputs the tree form results by default; they are elided here.
-sapling < test t
-DECODE -: "leaf"
-sapling < test (t t)
-DECODE -: "stem"
-sapling < test (t t t)
-DECODE -: "fork"
-sapling < map (\i : listConcat i " is super cool!") [("He") ("She") ("Everybody")]
-DECODE -: ["He is super cool!", "She is super cool!", "Everybody is super cool!"]
+tricu < -- Intensionality! We can inspect the structure of a function or data.
+tricu < triage = (\a b c : t (t a b) c)
+tricu < test = triage "Leaf" (\z : "Stem") (\a b : "Fork")
+tricu < test (t t)
+tricu > "Stem"
+tricu < -- We can even convert a term back to source code (/demos/toSource.tri)
+tricu < toSource not?
+tricu > "(t (t (t t) (t t t)) (t t (t t t)))"
+tricu < -- or calculate its size (/demos/size.tri)
+tricu < size not?
+tricu > 12
 ```
 
-## How to use
+## Installation and Use
 
-For now, you can easily build and run this project using Nix:
+[Releases are available for Linux.](https://git.eversole.co/James/tricu/releases)
 
-1. Clone the repository:
-    a. `git clone ssh://git.eversole.co/sapling.git`
-    b. `git clone https://git.eversole/sapling.git`
-1. Run the REPL: `nix run`
+Or you can easily build and/or run this project using [Nix](https://nixos.org/download/).
+
+- Quick Start (REPL): 
+  - `nix run git+https://git.eversole.co/James/tricu`
+- Build executable in `./result/bin`: 
+  - `nix build git+https://git.eversole.co/James/tricu`
+
+`./result/bin/tricu --help`
+
+```
+tricu Evaluator and REPL
+
+tricu [COMMAND] ... [OPTIONS]
+  tricu: Exploring Tree Calculus
+
+Common flags:
+  -? --help       Display help message
+  -V --version    Print version information
+
+tricu [repl] [OPTIONS]
+  Start interactive REPL
+
+tricu eval [OPTIONS]
+  Evaluate tricu and return the result of the final expression.
+
+  -f --file=FILE  Input file path(s) for evaluation.
+                    Defaults to stdin.
+  -t --form=FORM  Optional output form: (tree|fsl|ast|ternary|ascii|decode).
+                    Defaults to tricu-compatible `t` tree form.
+
+tricu decode [OPTIONS]
+  Decode a Tree Calculus value into a string representation.
+
+  -f --file=FILE  Optional input file path to attempt decoding.
+                    Defaults to stdin.
+```
 
 ## Acknowledgements 
 
 Tree Calculus was discovered by [Barry Jay](https://github.com/barry-jay-personal/blog). 
 
-[treecalcul.us](https://treecalcul.us) is an excellent website with an intuitive playground created by [Johannes Bader](https://johannes-bader.com/) that introduced me to Tree Calculus. If sapling sounds interesting but compiling this repo sounds like a hassle, you should check out his site.
+[treecalcul.us](https://treecalcul.us) is an excellent website with an intuitive Tree Calculus code playground created by [Johannes Bader](https://johannes-bader.com/) that introduced me to Tree Calculus.

demos/equality.tri

@@ -0,0 +1,41 @@
+!module Equality
+
+!import "lib/base.tri" Lib
+
+main = lambdaEqualsTC
+
+-- We represent `false` with a Leaf and `true` with a Stem Leaf
+demo_false = t
+demo_true  = t t
+
+-- Tree Calculus representation of the Boolean `not` function
+not_TC?     = t (t (t t) (t t t)) (t t (t t t))
+
+-- /demos/toSource.tri contains an explanation of `triage`
+demo_triage = \a b c : t (t a b) c
+demo_matchBool = (\ot of : demo_triage
+  of
+  (\_ : ot)
+  (\_ _ : ot)
+)
+-- Lambda representation of the Boolean `not` function
+not_Lambda? = demo_matchBool demo_false demo_true
+
+-- Since tricu eliminates Lambda terms to SKI combinators, the tree form of many
+-- functions defined via Lambda terms are larger than the most efficient TC
+-- representation. Between different languages that evaluate to tree calculus 
+-- terms, the exact implementation of Lambda elimination may differ and lead 
+-- to different tree representations even if they share extensional behavior.
+
+-- Let's see if these are the same:
+lambdaEqualsTC = Lib.equal? not_TC? not_Lambda?
+
+-- Here are some checks to verify their extensional behavior is the same:
+true_TC?  = not_TC? demo_false
+false_TC? = not_TC? demo_true
+
+true_Lambda?  = not_Lambda? demo_false
+false_Lambda? = not_Lambda? demo_true
+
+bothTrueEqual?  = Lib.equal? true_TC?  true_Lambda?
+bothFalseEqual? = Lib.equal? false_TC? false_Lambda?

demos/levelOrderTraversal.tri

@@ -0,0 +1,65 @@
+!module LOT
+
+!import "lib/base.tri" Lib
+
+main = exampleTwo
+-- Level Order Traversal of a labelled binary tree
+-- Objective: Print each "level" of the tree on a separate line
+--
+-- We model labelled binary trees as nested lists where values act as labels. We
+-- require explicit notation of empty nodes. Empty nodes can be represented
+-- with an empty list, `[]`, which evaluates to a single node `t`.
+--
+-- Example tree inputs:
+-- [("1") [("2") [("4") t t] t] [("3") [("5") t t] [("6") t t]]]]
+-- Graph:
+--       1
+--      / \
+--     2   3
+--    /   /  \
+--   4   5    6
+
+label = \node : Lib.head node
+
+left = (\node : Lib.if (Lib.emptyList? node)
+  [] 
+  (Lib.if (Lib.emptyList? (Lib.tail node)) 
+    [] 
+    (Lib.head (Lib.tail node))))
+
+right = (\node : Lib.if (Lib.emptyList? node) 
+  [] 
+  (Lib.if (Lib.emptyList? (Lib.tail node)) 
+    [] 
+    (Lib.if (Lib.emptyList? (Lib.tail (Lib.tail node))) 
+      [] 
+      (Lib.head (Lib.tail (Lib.tail node))))))
+
+processLevel = Lib.y (\self queue : Lib.if (Lib.emptyList? queue) 
+  [] 
+  (Lib.pair (Lib.map label queue) (self (Lib.filter 
+    (\node : Lib.not? (Lib.emptyList? node)) 
+      (Lib.lconcat (Lib.map left queue) (Lib.map right queue))))))
+
+levelOrderTraversal_ = \a : processLevel (t a t)
+
+toLineString = Lib.y (\self levels : Lib.if (Lib.emptyList? levels) 
+  "" 
+  (Lib.lconcat 
+    (Lib.lconcat (Lib.map (\x : Lib.lconcat x " ") (Lib.head levels)) "") 
+    (Lib.if (Lib.emptyList? (Lib.tail levels)) "" (Lib.lconcat (t (t 10 t) t) (self (Lib.tail levels))))))
+
+levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
+
+flatten = Lib.foldl (\acc x : Lib.lconcat acc x) ""
+
+levelOrderTraversal = \s : Lib.lconcat (t 10 t) (flatten (levelOrderToString s))
+
+exampleOne = levelOrderTraversal [("1") 
+                                 [("2") [("4") t t] t] 
+                                 [("3") [("5") t t] [("6") t t]]]
+
+exampleTwo = levelOrderTraversal [("1") 
+                                 [("2") [("4") [("8") t t] [("9") t t]] 
+                                        [("6") [("10") t t] [("12") t t]]] 
+                                 [("3") [("5") [("11") t t] t] [("7") t t]]]

demos/size.tri

@@ -0,0 +1,25 @@
+!module Size
+
+!import "lib/base.tri" Lib
+
+main = size size
+
+compose = \f g x : f (g x)
+
+succ = Lib.y (\self :
+  Lib.triage
+    1
+    t
+    (Lib.triage
+      (t (t t))
+      (\_ Lib.tail : t t (self Lib.tail))
+      t))
+
+size = (\x :
+  (Lib.y (\self x :
+    compose succ
+      (Lib.triage
+        (\x : x)
+        self
+        (\x y : compose (self x) (self y))
+        x)) x 0))

demos/toSource.tri

@@ -0,0 +1,51 @@
+!module ToSource
+
+!import "lib/base.tri" Lib
+
+main = toSource Lib.not?
+-- Thanks to intensionality, we can inspect the structure of a given value
+-- even if it's a function. This includes lambdas which are eliminated to
+-- Tree Calculus (TC) terms during evaluation.
+
+-- `triage` takes four arguments: the first three represent behaviors for each 
+-- structural case in Tree Calculus (Leaf, Stem, and Fork).
+-- The fourth argument is the value whose structure is inspected. By evaluating 
+-- the Tree Calculus term, `triage` enables branching logic based on the term's 
+-- shape, making it possible to perform structure-specific operations such as
+-- reconstructing the terms' source code representation.
+-- triage = (\leaf stem fork : t (t leaf stem) fork)
+
+-- Base case of a single Leaf
+sourceLeaf = t (Lib.head "t")
+
+-- Stem case
+sourceStem = (\convert : (\a rest :
+  t (Lib.head "(")                       -- Start with a left parenthesis "(".
+    (t (Lib.head "t")                    -- Add a "t"
+      (t (Lib.head " ")                  -- Add a space.
+        (convert a                       -- Recursively convert the argument.
+          (t (Lib.head ")") rest))))))   -- Close with ")" and append the rest.
+
+-- Fork case
+sourceFork = (\convert : (\a b rest :
+  t (Lib.head "(")                           -- Start with a left parenthesis "(".
+    (t (Lib.head "t")                        -- Add a "t"
+      (t (Lib.head " ")                      -- Add a space.
+        (convert a                           -- Recursively convert the first arg.
+          (t (Lib.head " ")                  -- Add another space.
+            (convert b                       -- Recursively convert the second arg.
+              (t (Lib.head ")") rest)))))))) -- Close with ")" and append the rest.
+
+-- Wrapper around triage 
+toSource_ = Lib.y (\self arg :
+  Lib.triage
+    sourceLeaf        -- `triage` "a" case, Leaf
+    (sourceStem self) -- `triage` "b" case, Stem
+    (sourceFork self) -- `triage` "c" case, Fork
+    arg)              -- The term to be inspected
+
+-- toSource takes a single TC term and returns a String
+toSource = \v : toSource_ v ""
+
+exampleOne = toSource Lib.true -- OUT: "(t t)"
+exampleTwo = toSource Lib.not? -- OUT: "(t (t (t t) (t t t)) (t t (t t t)))"

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "sapling";
+  description = "tricu";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs";
@@ -10,7 +10,7 @@
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs              = nixpkgs.legacyPackages.${system};
-        packageName       = "sapling";
+        packageName       = "tricu";
         containerPackageName = "${packageName}-container";
 
         customGHC = pkgs.haskellPackages.ghcWithPackages (hpkgs: with hpkgs; [
@@ -22,7 +22,7 @@
         enableSharedExecutables = false;
         enableSharedLibraries = false;
 
-        sapling = pkgs.haskell.lib.justStaticExecutables self.packages.${system}.default;
+        tricu = pkgs.haskell.lib.justStaticExecutables self.packages.${system}.default;
       in {
 
         packages.${packageName} =
@@ -32,10 +32,11 @@
         defaultPackage = self.packages.${system}.default;
 
         devShells.default = pkgs.mkShell {
-          buildInputs = with pkgs.haskellPackages; [
-            cabal-install
-            ghcid
+          buildInputs = with pkgs; [
+            haskellPackages.cabal-install
+            haskellPackages.ghcid
             customGHC
+            upx
           ];
           inputsFrom = builtins.attrValues self.packages.${system};
         };

lib/base.tri

@@ -0,0 +1,83 @@
+false = t
+_     = t
+true  = t t
+k     = t t
+i     = t (t k) t
+s     = t (t (k t)) t
+m     = s i i
+b     = s (k s) k
+c     = s (s (k s) (s (k k) s)) (k k)
+id    = \a : a
+pair  = t
+if    = \cond then else : t (t else (t t then)) t cond
+
+y = ((\mut wait fun : wait mut (\x : fun (wait mut x)))
+     (\x : x x)
+     (\a0 a1 a2 : t (t a0) (t t a2) a1))
+
+triage = \leaf stem fork : t (t leaf stem) fork
+test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
+
+matchBool = (\ot of : triage
+  of
+  (\_ : ot)
+  (\_ _ : ot)
+)
+
+matchList = \a b : triage a _ b
+
+matchPair = \a   : triage _ _ a
+
+not? = matchBool false true
+and? = matchBool id (\_ : false)
+emptyList? = matchList true (\_ _ : false)
+
+head = matchList t (\head _ : head)
+tail = matchList t (\_ tail : tail)
+
+lconcat = y (\self : matchList
+  (\k : k)
+  (\h r k : pair h (self r k)))
+
+lAnd = (triage
+  (\_     : false)
+  (\_ x   : x)
+  (\_ _ x : x))
+
+lOr = (triage
+  (\x     : x)
+  (\_ _   : true)
+  (\_ _ _ : true))
+
+map_ = y (\self :
+  matchList
+    (\_ : t)
+    (\head tail f : pair (f head) (self tail f)))
+map = \f l : map_ l f
+
+equal? = y (\self : triage
+  (triage
+    true
+    (\_   : false)
+    (\_ _ : false))
+  (\ax :
+    triage
+      false
+      (self ax)
+      (\_ _ : false))
+  (\ax ay :
+    triage
+      false
+      (\_ : false)
+      (\bx by : lAnd (self ax bx) (self ay by))))
+
+filter_ = y (\self : matchList
+  (\_ : t)
+  (\head tail f : matchBool (t head) i (f head) (self tail f)))
+filter  = \f l : filter_ l f
+
+foldl_ = y (\self f l x : matchList (\acc : acc) (\head tail acc : self f tail (f acc head)) l x)
+foldl  = \f x l : foldl_ f l x
+
+foldr_ = y (\self x f l : matchList x (\head tail : f (self x f tail) head) l)
+foldr  = \f x l : foldr_ x f l

shell.nix

@@ -1,8 +0,0 @@
-{ pkgs ? import <nixpkgs> {} }:
-let x = pkgs.haskellPackages.ghcWithPackages (hpkgs: with hpkgs; [
-		megaparsec
-  ]);
-in
-pkgs.mkShell {
-  buildInputs = [ x ];
-}

src/Eval.hs

@@ -3,118 +3,189 @@ module Eval where
 import Parser
 import Research
 
+import Data.List (partition, (\\))
 import Data.Map  (Map)
 import qualified Data.Map as Map
-import Data.List (foldl')
 import qualified Data.Set as Set
 
-evalSingle :: Map String T -> SaplingAST -> Map String T
-evalSingle env term = case term of
-  SFunc name [] body ->
-    let lineNoLambda = eliminateLambda body
-        result = evalAST env lineNoLambda
-    in Map.insert name result env
-  SLambda _ body ->
-    let result = evalAST env body
-    in Map.insert "__result" result env
-  SApp func arg ->
-    let result = apply (evalAST env $ eliminateLambda func) (evalAST env $ eliminateLambda arg)
-    in Map.insert "__result" result env
-  SVar name ->
+evalSingle :: Env -> TricuAST -> Env
+evalSingle env term
+  | SDef name [] body <- term =
+      if
+        | Map.member name env ->
+            errorWithoutStackTrace $
+              "Error: Identifier '" ++ name ++ "' is already defined."
+        | otherwise ->
+            let res = evalAST env body
+            in Map.insert "!result" res (Map.insert name res env)
+  | SApp func arg <- term =
+      let res = apply (evalAST env func) (evalAST env arg)
+      in Map.insert "!result" res env
+  | SVar name <- term =
       case Map.lookup name env of
-      Just value -> Map.insert "__result" value env
-      Nothing -> error $ "Variable " ++ name ++ " not defined"
-  _ ->
-    let result = evalAST env term
-    in Map.insert "__result" result env
+        Just v  ->
+          Map.insert "!result" v env
+        Nothing ->
+          errorWithoutStackTrace $ "Variable `" ++ name ++ "` not defined\n\
+          \This error should never occur here. Please report this as an issue."
+  | otherwise =
+      Map.insert "!result" (evalAST env term) env
 
-evalSapling :: Map String T -> [SaplingAST] -> Map String T
-evalSapling env [] = env
-evalSapling env [lastLine] =
-    let lastLineNoLambda = eliminateLambda lastLine
-        updatedEnv = evalSingle env lastLineNoLambda
-    in Map.insert "__result" (result updatedEnv) updatedEnv
-evalSapling env (line:rest) =
-    let lineNoLambda = eliminateLambda line
-        updatedEnv = evalSingle env lineNoLambda
-    in evalSapling updatedEnv rest
+evalTricu :: Env -> [TricuAST] -> Env
+evalTricu env x = go env (reorderDefs env x)
+  where
+    go env []     = env
+    go env [x]    =
+      let updatedEnv = evalSingle env x
+      in Map.insert "!result" (result updatedEnv) updatedEnv
+    go env (x:xs) =
+      evalTricu (evalSingle env x) xs
 
-evalAST :: Map String T -> SaplingAST -> T
-evalAST env term = case term of
-    SVar name -> case Map.lookup name env of
-        Just value -> value
-        Nothing -> error $ "Variable " ++ name ++ " not defined"
-    TLeaf -> Leaf
-    TStem t -> Stem (evalAST env t)
-    TFork t1 t2 -> Fork (evalAST env t1) (evalAST env t2)
-    SApp t1 t2 -> apply (evalAST env t1) (evalAST env t2)
-    SStr str -> ofString str
-    SInt num -> ofNumber num
-    SList elems -> ofList (map (evalAST Map.empty) elems)
-    SFunc name args body ->
-        error $ "Unexpected function definition " ++ name
-        ++ " in evalAST; define via evalSingle."
-    SLambda {} -> error "Internal error: SLambda found in evalAST after elimination."
+evalAST :: Env -> TricuAST -> T
+evalAST env term
+  | SLambda _ _ <- term = evalAST env (elimLambda term)
+  | SVar   name <- term = evalVar name
+  | TLeaf       <- term = Leaf
+  | TStem  t    <- term = Stem (evalAST env t)
+  | TFork  t u  <- term = Fork (evalAST env t) (evalAST env u)
+  | SApp   t u  <- term = apply (evalAST env t) (evalAST env u)
+  | SStr   s    <- term = ofString s
+  | SInt   n    <- term = ofNumber n
+  | SList  xs   <- term = ofList (map (evalAST env) xs)
+  | SEmpty      <- term = Leaf
+  | otherwise           = errorWithoutStackTrace "Unexpected AST term"
+    where
+      evalVar name = Map.findWithDefault
+        (errorWithoutStackTrace $ "Variable " ++ name ++ " not defined")
+        name env
 
-eliminateLambda :: SaplingAST -> SaplingAST
-eliminateLambda (SLambda (v:vs) body)
-  | null vs = lambdaToT v (eliminateLambda body)
-  | otherwise = eliminateLambda (SLambda [v] (SLambda vs body))
-eliminateLambda (SApp f arg) = SApp (eliminateLambda f) (eliminateLambda arg)
-eliminateLambda (TStem t) = TStem (eliminateLambda t)
-eliminateLambda (TFork l r) = TFork (eliminateLambda l) (eliminateLambda r)
-eliminateLambda (SList xs) = SList (map eliminateLambda xs)
-eliminateLambda other = other
+elimLambda :: TricuAST -> TricuAST
+elimLambda = go
+  where
+    -- η-reduction
+    go (SLambda [v] (SApp f (SVar x)))
+      | v == x && not (isFree v f) = elimLambda f
+    -- Triage optimization
+    go (SLambda [a] (SLambda [b] (SLambda [c] body)))
+      | body == triageBody         = _TRIAGE
+      where
+        triageBody =
+          (SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c))
+    -- Composition optimization
+    go (SLambda [f] (SLambda [g] (SLambda [x] body)))
+      | body == composeBody        = _COMPOSE
+      where
+        composeBody = SApp (SVar f) (SApp (SVar g) (SVar x))
+    -- General elimination
+    go (SLambda (v:vs) body)
+      | null vs                    = toSKI v (elimLambda body)
+      | otherwise                  = elimLambda (SLambda [v] (SLambda vs body))
+    go (SApp f g)                  = SApp (elimLambda f) (elimLambda g)
+    go x                           = x
 
--- This is my attempt to implement the lambda calculus elimination rules defined
--- in "Typed Program Analysis without Encodings" by Barry Jay.
--- https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf
-lambdaToT :: String -> SaplingAST -> SaplingAST
-lambdaToT x (SVar y)
-  | x == y = tI
-lambdaToT x (SVar y)
-  | x /= y = SApp tK (SVar y)
-lambdaToT x t
-  | not (isFree x t) = SApp tK t
-lambdaToT x (SApp n u)
-  | not (isFree x (SApp n u)) = SApp tK (SApp (eliminateLambda n) (eliminateLambda u))
-lambdaToT x (SApp n u) = SApp (SApp tS (lambdaToT x (eliminateLambda n))) (lambdaToT x (eliminateLambda u))
-lambdaToT x body
-  | not (isFree x body) = SApp tK body
-  | otherwise = SApp (SApp tS (lambdaToT x body)) TLeaf
+    toSKI x (SVar y)
+      | x == y           = _I
+      | otherwise        = SApp _K (SVar y)
+    toSKI x t@(SApp n u)
+      | not (isFree x t) = SApp _K t
+      | otherwise        = SApp (SApp _S (toSKI x n)) (toSKI x u)
+    toSKI x t
+      | not (isFree x t) = SApp _K t
+      | otherwise        = errorWithoutStackTrace "Unhandled toSKI conversion"
 
-freeVars :: SaplingAST -> Set.Set String
+    _S       = parseSingle "t (t (t t t)) t"
+    _K       = parseSingle "t t"
+    _I       = parseSingle "t (t (t t)) t"
+    _TRIAGE  = parseSingle "t (t (t t (t (t (t t t))))) t"
+    _COMPOSE = parseSingle "t (t (t t (t (t (t t t)) t))) (t t)"
+
+isFree :: String -> TricuAST -> Bool
+isFree x = Set.member x . freeVars
+
+freeVars :: TricuAST -> Set.Set String
 freeVars (SVar    v    ) = Set.singleton v
 freeVars (SInt    _    ) = Set.empty
 freeVars (SStr    _    ) = Set.empty
-freeVars (SList xs) = foldMap freeVars xs
-freeVars (SApp f arg) = freeVars f <> freeVars arg
-freeVars TLeaf = Set.empty
-freeVars (SFunc _ _ b) = freeVars b
+freeVars (SList   s    ) = foldMap freeVars s
+freeVars (SApp    f a  ) = freeVars f <> freeVars a
+freeVars (TLeaf        ) = Set.empty
+freeVars (SDef   _ _ b)  = freeVars b
 freeVars (TStem   t    ) = freeVars t
 freeVars (TFork   l r  ) = freeVars l <> freeVars r
-freeVars (SLambda vs b) = foldr Set.delete (freeVars b) vs
+freeVars (SLambda v b  ) = foldr Set.delete (freeVars b) v
+freeVars _               = Set.empty
 
-isFree :: String -> SaplingAST -> Bool
-isFree x = Set.member x . freeVars
+reorderDefs :: Env -> [TricuAST] -> [TricuAST]
+reorderDefs env defs
+  | not (null missingDeps) =
+      errorWithoutStackTrace $
+        "Missing dependencies detected: " ++ show missingDeps
+  | otherwise = orderedDefs ++ others
+  where
+    (defsOnly, others) = partition isDef defs
+    defNames = [ name | SDef name _ _ <- defsOnly ]
 
-toAST :: T -> SaplingAST
-toAST Leaf = TLeaf
-toAST (Stem a) = TStem (toAST a)
-toAST (Fork a b) = TFork (toAST a) (toAST b)
+    defsWithFreeVars = [(def, freeVars body) | def@(SDef _ _ body) <- defsOnly]
 
--- We need the SKI operators in an unevaluated SaplingAST tree form so that we
--- can keep the evaluation functions straightforward
-tI :: SaplingAST
-tI = SApp (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))) TLeaf
+    graph = buildDepGraph defsOnly
+    sortedDefs = sortDeps graph
+    defMap = Map.fromList [(name, def) | def@(SDef name _ _) <- defsOnly]
+    orderedDefs = map (\name -> defMap Map.! name) sortedDefs
 
-tK :: SaplingAST
-tK = SApp TLeaf TLeaf
+    freeVarsDefs = foldMap snd defsWithFreeVars
+    freeVarsOthers = foldMap freeVars others
+    allFreeVars = freeVarsDefs <> freeVarsOthers
+    validNames = Set.fromList defNames `Set.union` Set.fromList (Map.keys env)
+    missingDeps = Set.toList (allFreeVars `Set.difference` validNames)
 
-tS :: SaplingAST
-tS = SApp (SApp TLeaf (SApp TLeaf (SApp (SApp TLeaf TLeaf) TLeaf))) TLeaf
+    isDef (SDef _ _ _) = True
+    isDef _            = False
 
-result :: Map String T -> T
-result r = case Map.lookup "__result" r of
+buildDepGraph :: [TricuAST] -> Map.Map String (Set.Set String)
+buildDepGraph topDefs
+  | not (null duplicateNames) =
+      errorWithoutStackTrace $
+        "Duplicate definitions detected: " ++ show duplicateNames
+  | otherwise =
+      Map.fromList
+        [ (name, depends topDefs (SDef name [] body))
+        | SDef name _ body <- topDefs]
+  where
+    names = [name | SDef name _ _ <- topDefs]
+    duplicateNames =
+      [ name | (name, count) <- Map.toList (countOccurrences names) , count > 1]
+    countOccurrences = foldr (\x -> Map.insertWith (+) x 1) Map.empty
+
+sortDeps :: Map.Map String (Set.Set String) -> [String]
+sortDeps graph = go [] Set.empty (Map.keys graph)
+  where
+    go sorted sortedSet [] = sorted
+    go sorted sortedSet remaining =
+      let ready = [ name | name <- remaining
+                        , let deps = Map.findWithDefault Set.empty name graph
+                        , Set.isSubsetOf deps sortedSet ]
+          notReady = remaining \\ ready
+      in if null ready
+         then errorWithoutStackTrace
+          "ERROR: Cyclic dependency detected and prohibited.\n\
+          \RESOLVE: Use nested lambdas."
+         else go (sorted ++ ready)
+                 (Set.union sortedSet (Set.fromList ready))
+                 notReady
+
+depends :: [TricuAST] -> TricuAST -> Set.Set String
+depends topDefs (SDef _ _ body) =
+  Set.intersection
+    (Set.fromList [n | SDef n _ _ <- topDefs])
+    (freeVars body)
+depends _ _ = Set.empty
+
+result :: Env -> T
+result r = case Map.lookup "!result" r of
   Just a -> a
-    Nothing -> error "No __result field found in provided environment"
+  Nothing -> errorWithoutStackTrace "No !result field found in provided env"
+
+mainResult :: Env -> T
+mainResult r = case Map.lookup "main" r of
+  Just  a -> a
+  Nothing -> errorWithoutStackTrace "No valid definition for `main` found."

src/FileEval.hs

@@ -0,0 +1,150 @@
+module FileEval where
+
+import Eval
+import Lexer
+import Parser
+import Research
+
+import Data.List       (partition)
+import Control.Monad   (foldM)
+import System.IO
+
+import qualified Data.Map as Map
+import qualified Data.Set as Set
+
+evaluateFileResult :: FilePath -> IO T
+evaluateFileResult filePath = do
+  contents <- readFile filePath
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      let finalEnv = mainAlias moduleName $ evalTricu Map.empty ast
+      case Map.lookup "main" finalEnv of
+        Just finalResult -> return finalResult
+        Nothing -> errorWithoutStackTrace "No `main` function detected"
+
+evaluateFile :: FilePath -> IO Env
+evaluateFile filePath = do
+  contents <- readFile filePath
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      pure $ mainAlias moduleName $ evalTricu Map.empty ast
+
+evaluateFileWithContext :: Env -> FilePath -> IO Env
+evaluateFileWithContext env filePath = do
+  contents <- readFile filePath
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      pure $ mainAlias moduleName $ evalTricu env ast
+
+mainAlias :: String -> Env -> Env
+mainAlias "" env = env
+mainAlias moduleName env =
+  case Map.lookup (moduleName ++ ".main") env of
+    Just value -> Map.insert "main" value env
+    Nothing    -> env
+
+preprocessFile :: FilePath -> IO [TricuAST]
+preprocessFile filePath = preprocessFile' Set.empty filePath
+
+preprocessFile' :: Set.Set FilePath -> FilePath -> IO [TricuAST]
+preprocessFile' inProgress filePath
+  | filePath `Set.member` inProgress = 
+      errorWithoutStackTrace $ "Encountered cyclic import: " ++ filePath
+  | otherwise = do
+      contents <- readFile filePath
+      let tokens = lexTricu contents
+      case parseProgram tokens of
+        Left err -> errorWithoutStackTrace (handleParseError err)
+        Right asts -> do
+          let (moduleName, restAST) = extractModule asts
+          let (imports, nonImports) = partition isImport restAST
+          let newInProgress = Set.insert filePath inProgress
+          importedASTs <- concat <$> mapM (processImport newInProgress) imports
+          let namespacedAST = namespaceDefinitions moduleName nonImports
+          pure $ importedASTs ++ namespacedAST
+  where
+    extractModule :: [TricuAST] -> (String, [TricuAST])
+    extractModule ((SModule name) : xs) = (name, xs)
+    extractModule xs                    = ("", xs)
+
+    isImport :: TricuAST -> Bool
+    isImport (SImport _ _) = True
+    isImport _             = False
+
+    processImport :: Set.Set FilePath -> TricuAST -> IO [TricuAST]
+    processImport inProgress (SImport filePath moduleName) = do
+      importedAST <- preprocessFile' inProgress filePath
+      pure $ namespaceDefinitions moduleName importedAST
+    processImport _ _ = error "Unexpected non-import in processImport"
+
+namespaceDefinitions :: String -> [TricuAST] -> [TricuAST]
+namespaceDefinitions moduleName = map (namespaceDefinition moduleName)
+
+namespaceDefinition :: String -> TricuAST -> TricuAST
+namespaceDefinition "" def = def
+namespaceDefinition moduleName (SDef name args body)
+  | isPrefixed name = SDef name args (namespaceBody moduleName body)
+  | otherwise = SDef (namespaceVariable moduleName name) 
+                        args (namespaceBody moduleName body)
+namespaceDefinition moduleName other =
+  namespaceBody moduleName other
+
+namespaceBody :: String -> TricuAST -> TricuAST
+namespaceBody moduleName (SVar name)
+  | isPrefixed name = SVar name
+  | otherwise = SVar (namespaceVariable moduleName name)
+namespaceBody moduleName (SApp func arg) =
+  SApp (namespaceBody moduleName func) (namespaceBody moduleName arg)
+namespaceBody moduleName (SLambda args body) =
+  SLambda args (namespaceBodyScoped moduleName args body)
+namespaceBody moduleName (SList items) =
+  SList (map (namespaceBody moduleName) items)
+namespaceBody moduleName (TFork left right) =
+  TFork (namespaceBody moduleName left) (namespaceBody moduleName right)
+namespaceBody moduleName (TStem subtree) =
+  TStem (namespaceBody moduleName subtree)
+namespaceBody moduleName (SDef name args body)
+  | isPrefixed name = SDef name args (namespaceBody moduleName body)
+  | otherwise = SDef (namespaceVariable moduleName name) 
+                        args (namespaceBody moduleName body)
+namespaceBody _ other = other
+
+namespaceBodyScoped :: String -> [String] -> TricuAST -> TricuAST
+namespaceBodyScoped moduleName args body = case body of
+  SVar name ->
+    if name `elem` args
+      then SVar name
+      else namespaceBody moduleName (SVar name)
+  SApp func arg -> SApp (namespaceBodyScoped moduleName args func) (namespaceBodyScoped moduleName args arg)
+  SLambda innerArgs innerBody -> SLambda innerArgs (namespaceBodyScoped moduleName (args ++ innerArgs) innerBody)
+  SList items -> SList (map (namespaceBodyScoped moduleName args) items)
+  TFork left right -> TFork (namespaceBodyScoped moduleName args left) (namespaceBodyScoped moduleName args right)
+  TStem subtree -> TStem (namespaceBodyScoped moduleName args subtree)
+  SDef name innerArgs innerBody ->
+    SDef (namespaceVariable moduleName name) innerArgs (namespaceBodyScoped moduleName (args ++ innerArgs) innerBody)
+  other -> other
+
+isPrefixed :: String -> Bool
+isPrefixed name = '.' `elem` name
+
+namespaceVariable :: String -> String -> String
+namespaceVariable "" name = name
+namespaceVariable moduleName name = moduleName ++ "." ++ name

src/Lexer.hs

@@ -1,39 +1,30 @@
 module Lexer where
 
 import Research
-import Text.Megaparsec
-import Text.Megaparsec.Char
 
 import Control.Monad               (void)
 import Data.Void
+import Text.Megaparsec
+import Text.Megaparsec.Char hiding (space)
+import Text.Megaparsec.Char.Lexer
+
 import qualified Data.Set as Set
 
 type Lexer = Parsec Void String
 
-data LToken
-  = LKeywordT
-  | LIdentifier String
-  | LIntegerLiteral Int
-  | LStringLiteral String
-  | LAssign
-  | LColon
-  | LBackslash
-  | LOpenParen
-  | LCloseParen
-  | LOpenBracket
-  | LCloseBracket
-  | LNewline
-  | LComment String
-  deriving (Show, Eq, Ord)
-
 keywordT :: Lexer LToken
 keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
 
 identifier :: Lexer LToken
 identifier = do
-  name <- some (letterChar <|> char '_' <|> char '-')
-  if (name == "t" || name == "__result")
-    then fail "Keywords (`t`, `__result`) cannot be used as an identifier"
+  first <- letterChar <|> char '_'
+  rest  <- many $ letterChar 
+              <|> digitChar 
+              <|> char '_' <|> char '-' <|> char '?' <|> char '.'
+              <|> char '$' <|> char '#' <|> char '@' <|> char '%'
+  let name = first : rest
+  if (name == "t" || name == "!result")
+    then fail "Keywords (`t`, `!result`) cannot be used as an identifier"
     else return (LIdentifier name)
 
 integerLiteral :: Lexer LToken
@@ -45,12 +36,25 @@ stringLiteral :: Lexer LToken
 stringLiteral = do
   char '"'
   content <- many (noneOf ['"'])
-  if null content
-    then fail "Empty string literals are not allowed"
-    else do
   char '"' --"
   return (LStringLiteral content)
 
+lModule :: Lexer LToken
+lModule = do
+  _ <- string "!module"
+  space1
+  LIdentifier moduleName <- identifier
+  return (LModule moduleName)
+
+lImport :: Lexer LToken
+lImport = do
+  _ <- string "!import"
+  space1
+  LStringLiteral path <- stringLiteral
+  space1
+  LIdentifier name <- identifier
+  return (LImport path name)
+
 assign :: Lexer LToken
 assign = char '=' *> pure LAssign
 
@@ -75,20 +79,34 @@ closeBracket = char ']' *> pure LCloseBracket
 lnewline :: Lexer LToken
 lnewline = char '\n' *> pure LNewline
 
-comment :: Lexer LToken
-comment = do
-  string "--"
-  content <- many (satisfy (/= '\n'))
-  optional (char '\n')
-  pure (LComment content)
-
-
 sc :: Lexer ()
-sc = skipMany (void (char ' ') <|> void (char '\t') <|> void comment)
+sc = space
+  (void $ takeWhile1P (Just "space") (\c -> c == ' ' || c == '\t'))
+  (skipLineComment "--")
+  (skipBlockComment "|-" "-|")
 
-saplingLexer :: Lexer [LToken]
-saplingLexer = many (sc *> choice
-  [ try identifier
+tricuLexer :: Lexer [LToken]
+tricuLexer = do
+  sc
+  header <- many $ do
+    tok <- choice
+      [ try lModule
+      , try lImport
+      , lnewline
+      ]
+    sc
+    pure tok
+  tokens <- many $ do
+    tok <- choice tricuLexer'
+    sc
+    pure tok
+  sc
+  eof
+  pure (header ++ tokens)
+  where
+    tricuLexer' =
+      [ try lnewline
+      , try identifier
       , try keywordT
       , try integerLiteral
       , try stringLiteral
@@ -99,10 +117,9 @@ saplingLexer = many (sc *> choice
       , closeParen
       , openBracket
       , closeBracket
-  , lnewline
-  ] <* sc) <* eof
+      ]
 
-lexSapling :: String -> [LToken]
-lexSapling input = case runParser saplingLexer "" input of
-  Left err -> error $ "Lexical error:\n" ++ errorBundlePretty err
+lexTricu :: String -> [LToken]
+lexTricu input = case runParser tricuLexer "" input of
+  Left err -> errorWithoutStackTrace $ "Lexical error:\n" ++ errorBundlePretty err
   Right tokens -> tokens

src/Library.hs

@@ -1,47 +0,0 @@
-module Library where
-
-import Eval
-import Parser
-import Research
-
-import qualified Data.Map as Map
-
-library :: Map.Map String T
-library = evalSapling Map.empty $ parseSapling $ unlines 
-  [ "false = t" 
-  , "true = t t"
-  , "_ = t"
-  , "k = t t"
-  , "i = t (t k) t"
-  , "s = t (t (k t)) t"
-  , "m = s i i"
-  , "b = s (k s) k"
-  , "c = s (s (k s) (s (k k) s)) (k k)"
-  , "iC = (\\a b c : s a (k c) b)"
-  , "iD = b (b iC) iC"
-  , "iE = b (b iD) iC"
-  , "yi = (\\i : b m (c b (i m)))"
-  , "y = yi iC"
-  , "yC = yi iD"
-  , "yD = yi iE"
-  , "id = (\\a : a)"
-  , "triage = (\\a b c : t (t a b) c)"
-  , "pair = t"
-  , "matchBool = (\\ot of : triage of (\\_ : ot) (\\_ _ : ot))"
-  , "matchList = (\\oe oc : triage oe _ oc)"
-  , "matchPair = (\\op : triage _ _ op)"
-  , "and = matchBool id (\\z : false)"
-  , "if = (\\cond then else : t (t else (t t then)) t cond)"
-  , "test = triage \"leaf\" (\\z : \"stem\") (\\a b : \"fork\")"
-  , "emptyList = matchList true (\\y z : false)"
-  , "nonEmptyList = matchList false (\\y z : true)"
-  , "head = matchList t (\\hd tl : hd)"
-  , "tail = matchList t (\\hd tl : tl)"
-  , "isLeaf = (\\_ : triage true false false)"
-  , "listConcat = y (\\self : matchList (\\k : k) (\\h r k : pair h (self r k)))"
-  , "lAnd = triage (\\x : false) (\\_ x : x) (\\_ _ x : x)"
-  , "lOr = triage (\\x : x) (\\_ _ : true) (\\_ _ x : true)"
-  , "hmap = y (\\self : matchList (\\f : t) (\\hd tl f : pair (f hd) (self tl f)))"
-  , "map = (\\f l : hmap l f)"
-  , "equal = y (\\self : triage (triage true (\\z : false) (\\y z : false)) (\\ax : triage false (self ax) (\\y z : false)) (\\ax ay : triage false (\\z : false) (\\bx by : lAnd (self ax bx) (self ay by))))" 
-  ]

src/Main.hs

@@ -1,22 +1,87 @@
 module Main where
 
-import Eval
-import Lexer
-import Library
-import Parser
-import REPL (repl)
+import Eval                   (evalTricu, mainResult, result)
+import FileEval
+import Parser                 (parseTricu)
+import REPL
 import Research
 
-import qualified Data.Map as Map
+import Control.Monad          (foldM)
+import Control.Monad.IO.Class (liftIO)
 import Text.Megaparsec        (runParser)
+import System.Console.CmdArgs
+
+import qualified Data.Map as Map
+
+data TricuArgs
+  = Repl
+  | Evaluate { file :: [FilePath], form :: EvaluatedForm }
+  | TDecode { file :: [FilePath] }
+  deriving (Show, Data, Typeable)
+
+replMode :: TricuArgs
+replMode = Repl
+  &= help "Start interactive REPL"
+  &= auto
+  &= name "repl"
+
+evaluateMode :: TricuArgs
+evaluateMode = Evaluate
+  { file = def &= help "Input file path(s) for evaluation.\n \
+      \ Defaults to stdin."
+      &= name "f" &= typ "FILE"
+    , form = TreeCalculus &= typ "FORM"
+      &= help "Optional output form: (tree|fsl|ast|ternary|ascii|decode).\n \
+      \ Defaults to tricu-compatible `t` tree form."
+      &= name "t"
+  }
+  &= help "Evaluate tricu and return the result of the final expression."
+  &= explicit
+  &= name "eval"
+
+decodeMode :: TricuArgs
+decodeMode = TDecode
+  { file = def
+    &= help "Optional input file path to attempt decoding.\n \
+    \ Defaults to stdin."
+    &= name "f" &= typ "FILE"
+  }
+  &= help "Decode a Tree Calculus value into a string representation."
+  &= explicit
+  &= name "decode"
 
 main :: IO ()
 main = do
-  putStrLn "Welcome to the Sapling Interpreter"
-  putStrLn "You can exit at any time by typing and entering: "
-  putStrLn ":_exit"
-  repl library
+  args <- cmdArgs $ modes [replMode, evaluateMode, decodeMode]
+    &= help "tricu: Exploring Tree Calculus"
+    &= program "tricu"
+    &= summary "tricu Evaluator and REPL"
+  case args of
+    Repl -> do
+      putStrLn "Welcome to the tricu REPL"
+      putStrLn "You can exit with `CTRL+D` or the `:_exit` command.`"
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      repl $ Map.delete "!result" library
+    Evaluate { file = filePaths, form = form } -> do
+      result <- case filePaths of
+        [] -> do
+          t <- getContents
+          pure $ runTricu t
+        (filePath:restFilePaths) -> do
+            initialEnv <- evaluateFile filePath
+            finalEnv <- foldM evaluateFileWithContext initialEnv restFilePaths
+            pure $ mainResult finalEnv
+      let fRes = formatResult form result
+      putStr fRes
+    TDecode { file = filePaths } -> do
+      value <- case filePaths of
+        [] -> getContents
+        (filePath:_) -> readFile filePath
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      putStrLn $ decodeResult $ result $ evalTricu library $ parseTricu value
 
-runSapling :: String -> T
-runSapling s = result (evalSapling Map.empty $ parseSapling s)
-runSaplingEnv env s = result (evalSapling env $ parseSapling s)
+runTricu :: String -> T
+runTricu input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+   in result finalEnv

src/Parser.hs

@@ -1,255 +1,316 @@
 module Parser where
 
-import Debug.Trace
 import Lexer
-import Research hiding (toList)
-import Control.Exception (throw)
+import Research
+
+import Control.Monad (void)
+import Control.Monad.State
 import Data.List.NonEmpty (toList)
-import qualified Data.Set as Set
-import Data.Void
+import Data.Void (Void)
 import Text.Megaparsec
-import Text.Megaparsec.Char
-import Text.Megaparsec.Error (errorBundlePretty, ParseErrorBundle)
+import Text.Megaparsec.Error (ParseErrorBundle, errorBundlePretty)
+import qualified Data.Set as Set
 
-type Parser = Parsec Void [LToken]
+data PState = PState
+  { parenDepth  :: Int
+  , bracketDepth :: Int
+  } deriving (Show)
 
-data SaplingAST
-  = SVar String
-  | SInt Int
-  | SStr String
-  | SList [SaplingAST]
-  | SFunc String [String] SaplingAST
-  | SApp SaplingAST SaplingAST
-  | TLeaf
-  | TStem SaplingAST
-  | TFork SaplingAST SaplingAST
-  | SLambda [String] SaplingAST
-  deriving (Show, Eq, Ord)
+type ParserM = StateT PState (Parsec Void [LToken])
 
-parseSapling :: String -> [SaplingAST]
-parseSapling input =
-  let nonEmptyLines = filter (not . null) (lines input)
-  in map parseSingle nonEmptyLines
+satisfyM :: (LToken -> Bool) -> ParserM LToken
+satisfyM f = do
+  token <- lift (satisfy f)
+  modify' (updateDepth token)
+  return token
 
-parseSingle :: String -> SaplingAST
-parseSingle input = case runParser parseExpression "" (lexSapling input) of
-  Left err -> error $ handleParseError err
+updateDepth :: LToken -> PState -> PState
+updateDepth LOpenParen    st = st { parenDepth   = parenDepth st   + 1 }
+updateDepth LOpenBracket  st = st { bracketDepth = bracketDepth st + 1 }
+updateDepth LCloseParen   st = st { parenDepth   = parenDepth st   - 1 }
+updateDepth LCloseBracket st = st { bracketDepth = bracketDepth st - 1 }
+updateDepth _ st = st
+
+topLevelNewline :: ParserM ()
+topLevelNewline = do
+  st <- get
+  if parenDepth st == 0 && bracketDepth st == 0
+    then void (satisfyM (== LNewline))
+    else fail "Top-level exit in nested context (paren or bracket)"
+
+parseProgram :: [LToken] -> Either (ParseErrorBundle [LToken] Void) [TricuAST]
+parseProgram tokens =
+  runParser (evalStateT (parseProgramM <* finalizeDepth <* eof) (PState 0 0)) "" tokens
+
+parseSingleExpr :: [LToken] -> Either (ParseErrorBundle [LToken] Void) TricuAST
+parseSingleExpr tokens =
+  runParser (evalStateT (scnParserM *> parseExpressionM <* finalizeDepth <* eof) (PState 0 0)) "" tokens
+
+finalizeDepth :: ParserM ()
+finalizeDepth = do
+  st <- get
+  case (parenDepth st, bracketDepth st) of
+    (0, 0) -> pure ()
+    (p, b) -> fail $ "Unmatched tokens: " ++ show (p, b)
+
+parseTricu :: String -> [TricuAST]
+parseTricu input =
+  case lexTricu input of
+    [] -> []
+    toks ->
+      case parseProgram toks of
+        Left err   -> errorWithoutStackTrace (handleParseError err)
+        Right asts -> asts
+
+parseSingle :: String -> TricuAST
+parseSingle input =
+  case lexTricu input of
+    [] -> SEmpty
+    toks ->
+      case parseSingleExpr toks of
+        Left err -> errorWithoutStackTrace (handleParseError err)
         Right ast -> ast
 
-scnParser :: Parser ()
-scnParser = skipMany (satisfy isNewline)
+parseProgramM :: ParserM [TricuAST]
+parseProgramM = do
+  skipMany topLevelNewline
+  moduleNode <- optional parseModuleM
+  skipMany topLevelNewline
+  importNodes <- many (do
+    node <- parseImportM
+    skipMany topLevelNewline
+    return node)
+  skipMany topLevelNewline
+  exprs <- sepEndBy parseOneExpression (some topLevelNewline)
+  skipMany topLevelNewline
+  return (maybe [] (: []) moduleNode ++ importNodes ++ exprs)
 
-parseExpression :: Parser SaplingAST
-parseExpression = choice
-  [ try parseFunction
-  , try parseLambda
-  , try parseLambdaExpression
-  , try parseListLiteral
-  , try parseApplication
-  , try parseTreeTerm
-  , parseLiteral
+
+parseModuleM :: ParserM TricuAST
+parseModuleM = do
+  LModule moduleName <- satisfyM isModule
+  pure (SModule moduleName)
+  where
+    isModule (LModule _) = True
+    isModule _           = False
+
+parseImportM :: ParserM TricuAST
+parseImportM = do
+  LImport filePath moduleName <- satisfyM isImport
+  pure (SImport filePath moduleName)
+  where
+    isImport (LImport _ _) = True
+    isImport _             = False
+
+parseOneExpression :: ParserM TricuAST
+parseOneExpression = scnParserM *> parseExpressionM
+
+scnParserM :: ParserM ()
+scnParserM = skipMany $ do
+  t  <- lookAhead anySingle
+  st <- get
+  if | (parenDepth st > 0 || bracketDepth st > 0) && (t == LNewline) ->
+       void $ satisfyM (== LNewline)
+     | otherwise ->
+       fail "In nested context or no space token" <|> empty
+
+eofM :: ParserM ()
+eofM = lift eof
+
+parseExpressionM :: ParserM TricuAST
+parseExpressionM = choice
+  [ try parseFunctionM
+  , try parseLambdaM
+  , try parseLambdaExpressionM
+  , try parseListLiteralM
+  , try parseApplicationM
+  , try parseTreeTermM
+  , parseLiteralM
   ]
 
-parseFunction :: Parser SaplingAST
-parseFunction = do
-  LIdentifier name <- satisfy isIdentifier
-  args <- many (satisfy isIdentifier)
-  satisfy (== LAssign)
-  body <- parseExpression
-  return (SFunc name (map getIdentifier args) body)
+parseFunctionM :: ParserM TricuAST
+parseFunctionM = do
+  let ident = (\case LIdentifier _ -> True; _ -> False)
+  LIdentifier name <- satisfyM ident
+  args <- many $ satisfyM ident
+  _    <- satisfyM (== LAssign)
+  scnParserM
+  body <- parseExpressionM
+  pure (SDef name (map getIdentifier args) body)
 
-parseAtomicBase :: Parser SaplingAST
-parseAtomicBase = choice
-    [ try parseVarWithoutAssignment
-    , parseTreeLeaf
-    , parseGrouped
-    ]
-parseVarWithoutAssignment :: Parser SaplingAST
-parseVarWithoutAssignment = do
-    LIdentifier name <- satisfy isIdentifier
-    if (name == "t" || name == "__result")
-    then fail $ "Reserved keyword: " ++ name ++ " cannot be assigned."
-    else notFollowedBy (satisfy (== LAssign)) *> return (SVar name)
+parseLambdaM :: ParserM TricuAST
+parseLambdaM = do
+  let ident = (\case LIdentifier _ -> True; _ -> False)
+  _      <- satisfyM (== LBackslash)
+  params <- some (satisfyM ident)
+  _      <- satisfyM (== LColon)
+  scnParserM
+  body  <- parseLambdaExpressionM
+  pure $ foldr (\param acc -> SLambda [getIdentifier param] acc) body params
 
-parseLambda :: Parser SaplingAST
-parseLambda = between (satisfy (== LOpenParen)) (satisfy (== LCloseParen)) $ do
-  satisfy (== LBackslash)
-  param    <- satisfy isIdentifier
-  rest     <- many (satisfy isIdentifier)
-  satisfy (== LColon)
-  body     <- parseLambdaExpression
-  let nestedLambda = foldr (\v acc -> SLambda [v] acc) body (map getIdentifier rest)
-  return (SLambda [getIdentifier param] nestedLambda)
-
-parseLambdaExpression :: Parser SaplingAST
-parseLambdaExpression = choice
-  [ try parseLambdaApplication
-  , parseAtomicLambda
+parseLambdaExpressionM :: ParserM TricuAST
+parseLambdaExpressionM = choice
+  [ try parseLambdaApplicationM
+  , parseAtomicLambdaM
   ]
 
-parseAtomicLambda :: Parser SaplingAST
-parseAtomicLambda = choice
-  [ parseVar
-  , parseTreeLeaf
-  , parseLiteral
-  , parseListLiteral
-  , try parseLambda
-  , between (satisfy (== LOpenParen)) (satisfy (== LCloseParen)) parseLambdaExpression
+parseAtomicLambdaM :: ParserM TricuAST
+parseAtomicLambdaM = choice
+  [ parseVarM
+  , parseTreeLeafM
+  , parseLiteralM
+  , parseListLiteralM
+  , try parseLambdaM
+  , between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseLambdaExpressionM
   ]
 
-parseApplication :: Parser SaplingAST
-parseApplication = do
-  func <- parseAtomicBase
-  args <- many parseAtomic
-  return $ foldl (\acc arg -> SApp acc arg) func args
+parseApplicationM :: ParserM TricuAST
+parseApplicationM = do
+  func <- parseAtomicBaseM
+  scnParserM
+  args <- many $ do
+    scnParserM
+    arg <- parseAtomicM
+    return arg
+  return $ foldl SApp func args
 
-parseLambdaApplication :: Parser SaplingAST
-parseLambdaApplication = do
-  func <- parseAtomicLambda
-  args <- many parseAtomicLambda
-  return $ foldl (\acc arg -> SApp acc arg) func args
+parseLambdaApplicationM :: ParserM TricuAST
+parseLambdaApplicationM = do
+  func <- parseAtomicLambdaM
+  scnParserM
+  args <- many $ do
+    arg <- parseAtomicLambdaM
+    scnParserM
+    pure arg
+  pure $ foldl SApp func args
 
-isTreeTerm :: SaplingAST -> Bool
-isTreeTerm TLeaf = True
-isTreeTerm (TStem _) = True
-isTreeTerm (TFork _ _) = True
-isTreeTerm _ = False
+parseAtomicBaseM :: ParserM TricuAST
+parseAtomicBaseM = choice
+  [ parseTreeLeafM
+  , parseGroupedM
+  ]
 
-parseTreeLeaf :: Parser SaplingAST
-parseTreeLeaf = satisfy isKeywordT *> notFollowedBy (satisfy (== LAssign)) *> pure TLeaf
+parseTreeLeafM :: ParserM TricuAST
+parseTreeLeafM = do
+  let keyword = (\case LKeywordT -> True; _ -> False)
+  _ <- satisfyM keyword
+  notFollowedBy $ lift $ satisfy (== LAssign)
+  pure TLeaf
+
+parseTreeTermM :: ParserM TricuAST
+parseTreeTermM = do
+  base <- parseTreeLeafOrParenthesizedM
+  rest <- many parseTreeLeafOrParenthesizedM
+  pure (foldl combine base rest)
+  where
+    combine acc next
+      | TLeaf     <- acc = TStem next
+      | TStem t   <- acc = TFork t next
+      | TFork _ _ <- acc = TFork acc next
+
+parseTreeLeafOrParenthesizedM :: ParserM TricuAST
+parseTreeLeafOrParenthesizedM = choice
+  [ between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseTreeTermM
+  , parseTreeLeafM
+  ]
+
+parseAtomicM :: ParserM TricuAST
+parseAtomicM = choice
+  [ parseVarM
+  , parseTreeLeafM
+  , parseListLiteralM
+  , parseGroupedM
+  , parseLiteralM
+  ]
+
+parseGroupedM :: ParserM TricuAST
+parseGroupedM = between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) $
+  scnParserM *> parseExpressionM <* scnParserM
+
+parseLiteralM :: ParserM TricuAST
+parseLiteralM = choice
+  [ parseIntLiteralM
+  , parseStrLiteralM
+  ]
+
+parseListLiteralM :: ParserM TricuAST
+parseListLiteralM = do
+  _        <- satisfyM (== LOpenBracket)
+  elements <- many $ do
+    scnParserM
+    parseListItemM
+  scnParserM
+  _        <- satisfyM (== LCloseBracket)
+  pure (SList elements)
+
+parseListItemM :: ParserM TricuAST
+parseListItemM = choice
+  [ parseGroupedItemM
+  , parseListLiteralM
+  , parseSingleItemM
+  ]
+
+parseGroupedItemM :: ParserM TricuAST
+parseGroupedItemM = do
+  _     <- satisfyM (== LOpenParen)
+  inner <- parseExpressionM
+  _     <- satisfyM (== LCloseParen)
+  pure inner
+
+parseSingleItemM :: ParserM TricuAST
+parseSingleItemM = do
+  token <- satisfyM (\case LIdentifier _ -> True; LKeywordT -> True; _ -> False)
+  if | LIdentifier name <- token -> pure (SVar name)
+     | token == LKeywordT        -> pure TLeaf
+     | otherwise                 -> fail "Unexpected token in list item"
+
+parseVarM :: ParserM TricuAST
+parseVarM = do
+  satisfyM (\case LIdentifier _ -> True; _ -> False) >>= \case
+    LIdentifier name
+      | name == "t" || name == "!result" ->
+        fail ("Reserved keyword: " ++ name ++ " cannot be assigned.")
+      | otherwise                         ->
+         pure (SVar name)
+    _ -> fail "Unexpected token while parsing variable"
+
+parseIntLiteralM :: ParserM TricuAST
+parseIntLiteralM = do
+  let intL = (\case LIntegerLiteral _ -> True; _ -> False)
+  token <- satisfyM intL
+  if | LIntegerLiteral value <- token ->
+       pure (SInt value)
+     | otherwise                      ->
+       fail "Unexpected token while parsing integer literal"
+
+parseStrLiteralM :: ParserM TricuAST
+parseStrLiteralM = do
+  let strL = (\case LStringLiteral _ -> True; _ -> False)
+  token <- satisfyM strL
+  if | LStringLiteral value <- token ->
+       pure (SStr value)
+     | otherwise                     ->
+       fail "Unexpected token while parsing string literal"
 
 getIdentifier :: LToken -> String
 getIdentifier (LIdentifier name) = name
-getIdentifier _ = error "Expected identifier"
+getIdentifier _                  = errorWithoutStackTrace "Expected identifier"
 
-parseTreeTerm :: Parser SaplingAST
-parseTreeTerm = do
-  base <- parseTreeLeafOrParenthesized
-  rest <- many parseTreeLeafOrParenthesized
-  pure $ foldl combine base rest
-  where
-    combine acc next = case acc of
-      TLeaf -> TStem next
-      TStem t -> TFork t next
-      TFork _ _ -> TFork acc next
-
-parseTreeLeafOrParenthesized :: Parser SaplingAST
-parseTreeLeafOrParenthesized = choice
-  [ between (satisfy (== LOpenParen)) (satisfy (== LCloseParen)) parseTreeTerm
-  , parseTreeLeaf
-  ]
-
-foldTree :: [SaplingAST] -> SaplingAST
-foldTree [] = TLeaf
-foldTree [x] = x
-foldTree (x:y:rest) = TFork x (foldTree (y:rest))
-
-parseAtomic :: Parser SaplingAST
-parseAtomic = choice
-  [ parseVar
-  , parseTreeLeaf
-  , parseListLiteral
-  , parseGrouped
-  , parseLiteral
-  ]
-
-parseGrouped :: Parser SaplingAST
-parseGrouped = between (satisfy (== LOpenParen)) (satisfy (== LCloseParen)) parseExpression
-
-parseLiteral :: Parser SaplingAST
-parseLiteral = choice
-  [ parseIntLiteral
-  , parseStrLiteral
-  ]
-
-parens :: Parser SaplingAST -> Parser SaplingAST
-parens p = do
-  satisfy (== LOpenParen)
-  result <- p
-  satisfy (== LCloseParen)
-  return result
-
-parseListLiteral :: Parser SaplingAST
-parseListLiteral = do
-  satisfy (== LOpenBracket)
-  elements <- many parseListItem
-  satisfy (== LCloseBracket)
-  return (SList elements)
-
-parseListItem :: Parser SaplingAST
-parseListItem = choice
-  [ parseGroupedItem
-  , parseListLiteral
-  , parseSingleItem
-  ]
-
-parseGroupedItem :: Parser SaplingAST
-parseGroupedItem = do
-  satisfy (== LOpenParen)
-  inner <- parseExpression
-  satisfy (== LCloseParen)
-  return inner
-
-parseSingleItem :: Parser SaplingAST
-parseSingleItem = do
-  token <- satisfy isListItem
-  case token of
-    LIdentifier name -> return (SVar name)
-    LKeywordT -> return TLeaf
-    _ -> fail "Unexpected token in list item"
-
-isListItem :: LToken -> Bool
-isListItem (LIdentifier _) = True
-isListItem LKeywordT = True
-isListItem _ = False
-
-parseVar :: Parser SaplingAST
-parseVar = do
-  LIdentifier name <- satisfy isIdentifier
-  if (name == "t" || name == "__result")
-    then fail $ "Reserved keyword: " ++ name ++ " cannot be assigned."
-    else return (SVar name)
-
-parseIntLiteral :: Parser SaplingAST
-parseIntLiteral = do
-  LIntegerLiteral value <- satisfy isIntegerLiteral
-  return (SInt value)
-
-parseStrLiteral :: Parser SaplingAST
-parseStrLiteral = do
-  LStringLiteral value <- satisfy isStringLiteral
-  return (SStr value)
-
--- Boolean Helpers
-isKeywordT (LKeywordT) = True
-isKeywordT _ = False
-isIdentifier (LIdentifier _) = True
-isIdentifier _ = False
-isIntegerLiteral (LIntegerLiteral _) = True
-isIntegerLiteral _ = False
-isStringLiteral (LStringLiteral _) = True
-isStringLiteral _ = False
-isLiteral (LIntegerLiteral _) = True
-isLiteral (LStringLiteral _) = True
-isLiteral _ = False
-isNewline (LNewline) = True
-isNewline _ = False
-
--- Error Handling
 handleParseError :: ParseErrorBundle [LToken] Void -> String
 handleParseError bundle =
   let errors = bundleErrors bundle
-      errorList = toList errors
-      formattedErrors = map showError errorList
+      formattedErrors = map formatError (Data.List.NonEmpty.toList errors)
   in unlines ("Parse error(s) encountered:" : formattedErrors)
 
-showError :: ParseError [LToken] Void -> String
-showError (TrivialError offset (Just (Tokens tokenStream)) expected) =
-  "Parse error at offset " ++ show offset ++ ": unexpected token "
-  ++ show tokenStream ++ ", expected one of " ++ show (Set.toList expected)
-showError (FancyError offset fancy) =
-  "Parse error at offset " ++ show offset ++ ":\n " ++ unlines (map show (Set.toList fancy))
-showError (TrivialError offset Nothing expected) =
-  "Parse error at offset " ++ show offset ++ ": expected one of "
-  ++ show (Set.toList expected)
-
+formatError :: ParseError [LToken] Void -> String
+formatError (TrivialError offset unexpected expected) =
+  let unexpectedMsg = case unexpected of
+        Just x  -> "unexpected token " ++ show x
+        Nothing -> "unexpected end of input"
+      expectedMsg = if null expected
+        then ""
+        else "expected " ++ show (Set.toList expected)
+  in "Parse error at offset " ++ show offset ++ ": " ++ unexpectedMsg ++
+     if null expectedMsg then "" else " " ++ expectedMsg
+formatError (FancyError offset _) =
+  "Parse error at offset " ++ show offset ++ ": unexpected FancyError"

src/REPL.hs

@@ -1,42 +1,61 @@
 module REPL where
 
 import Eval
+import FileEval
 import Lexer
 import Parser
 import Research
 
-import Data.List                 (intercalate)
-import qualified Data.Map as Map
+import Control.Exception         (SomeException, catch)
+import Control.Monad.IO.Class    (liftIO)
+import Data.Char                 (isSpace)
+import Data.List                 (dropWhile, dropWhileEnd, intercalate)
 import System.Console.Haskeline
-import System.IO                 (hFlush, stdout)
 
-repl :: Map.Map String T -> IO ()
+import qualified Data.Map as Map
+
+repl :: Env -> IO ()
 repl env = runInputT defaultSettings (loop env)
   where
-    loop :: Map.Map String T -> InputT IO ()
+    loop :: Env -> InputT IO ()
     loop env = do
-      minput <- getInputLine "sapling < "
-      case minput of
-        Nothing -> outputStrLn "Goodbye!"
-        Just ":_exit" -> outputStrLn "Goodbye!"
-        Just "" -> do
+      minput <- getInputLine "tricu < "
+      if
+        | Nothing <- minput                     -> outputStrLn "Exiting tricu"
+        | Just s  <- minput, strip s == "!exit" -> outputStrLn "Exiting tricu"
+        | Just s  <- minput, strip s == ""      -> do
           outputStrLn ""
           loop env
-        Just input -> do
-          let clearEnv = Map.delete "__result" env
-              newEnv   = evalSingle clearEnv (parseSingle input)
-          case Map.lookup "__result" newEnv of
-            Just r -> do
-              outputStrLn $ "sapling > " ++ show r
-              outputStrLn $ "DECODE -: " ++ decodeResult r
-            Nothing -> return ()
+        | Just s  <- minput, strip s == "!import" -> do
+          path <- getInputLine "File path to load < "
+          if
+            | Nothing <- path -> do
+              outputStrLn "No input received; stopping import."
+              loop env
+            | Just p  <- path -> do
+              loadedEnv <- liftIO $ evaluateFileWithContext env (strip p) `catch` \e -> errorHandler env e
+              loop $ Map.delete "!result" (Map.union loadedEnv env)
+        | Just s <- minput -> do
+          if
+            | take 2 s == "--" -> loop env
+            | otherwise -> do
+              newEnv <- liftIO $ processInput env s `catch` errorHandler env
               loop newEnv
 
-decodeResult :: T -> String
-decodeResult tc = case toNumber tc of
-  Right num -> show num
-  Left _ -> case toString tc of
-    Right str -> "\"" ++ str ++ "\""
-    Left _ -> case toList tc of
-      Right list -> "[" ++ intercalate ", " (map decodeResult list) ++ "]"
-      Left _ -> ""
+    processInput :: Env -> String -> IO Env
+    processInput env input = do
+      let asts   = parseTricu input
+          newEnv = evalTricu env asts
+      if
+        | Just r <- Map.lookup "!result" newEnv -> do
+          putStrLn $ "tricu > " ++ decodeResult r
+        | otherwise -> return ()
+      return newEnv
+    
+    errorHandler :: Env -> SomeException -> IO (Env)
+    errorHandler env e = do
+      putStrLn $ "Error: " ++ show e
+      return env
+    
+    strip :: String -> String
+    strip = dropWhileEnd isSpace . dropWhile isSpace

src/Research.hs

@@ -1,13 +1,61 @@
 module Research where
 
-import Data.List (intercalate)
 import Control.Monad.State
-import qualified Data.Map as Map
+import Data.List                 (intercalate)
 import Data.Map                  (Map)
+import Data.Text                 (Text, replace)
+import System.Console.CmdArgs    (Data, Typeable)
 
+import qualified Data.Map        as Map
+import qualified Data.Text as T
+
+-- Tree Calculus Types
 data T = Leaf | Stem T | Fork T T
   deriving (Show, Eq, Ord)
 
+-- Abstract Syntax Tree for tricu
+data TricuAST
+  = SVar String
+  | SInt Int
+  | SStr String
+  | SList [TricuAST]
+  | SDef String [String] TricuAST
+  | SApp TricuAST TricuAST
+  | TLeaf
+  | TStem TricuAST
+  | TFork TricuAST TricuAST
+  | SLambda [String] TricuAST
+  | SEmpty
+  | SModule String
+  | SImport String String
+  deriving (Show, Eq, Ord)
+
+-- Lexer Tokens
+data LToken
+  = LKeywordT
+  | LIdentifier String
+  | LIntegerLiteral Int
+  | LStringLiteral String
+  | LAssign
+  | LColon
+  | LBackslash
+  | LOpenParen
+  | LCloseParen
+  | LOpenBracket
+  | LCloseBracket
+  | LNewline
+  | LModule String
+  | LImport String String
+  deriving (Show, Eq, Ord)
+
+-- Output formats
+data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii | Decode
+  deriving (Show, Data, Typeable)
+
+-- Environment containing previously evaluated TC terms
+type Env = Map.Map String T 
+
+-- Tree Calculus Reduction
 apply :: T -> T -> T
 apply Leaf b                            = Stem b
 apply (Stem a) b                        = Fork a b
@@ -17,29 +65,6 @@ apply (Fork (Fork a1 a2) a3) Leaf       = a1
 apply (Fork (Fork a1 a2) a3) (Stem u)   = apply a2 u
 apply (Fork (Fork a1 a2) a3) (Fork u v) = apply (apply a3 u) v
 
-reduce :: T -> T
-reduce expr =
-  let next = step expr
-  in if next == expr then expr else reduce next
-
-step :: T -> T
-step (Fork left right) = reduce (apply (reduce left) (reduce right))
-step (Stem inner) = Stem (reduce inner)
-step t = t
-
--- SKI Combinators
-_S :: T
-_S = Fork (Stem (Fork Leaf Leaf)) Leaf
-
-_K :: T
-_K = Stem Leaf
-
--- Identity
--- We use the "point-free" style which drops a redundant node
--- Full _I form (SKK): Fork (Stem (Stem Leaf)) (Stem Leaf)
-_I :: T
-_I = Fork (Stem (Stem Leaf)) Leaf 
-
 -- Booleans
 _false :: T
 _false = Leaf
@@ -87,7 +112,32 @@ toList (Fork x rest) = case toList rest of
   Left err -> Left err
 toList _ = Left "Invalid Tree Calculus list"
 
--- Utility
+-- Outputs
+formatResult :: EvaluatedForm -> T -> String
+formatResult TreeCalculus = toSimpleT . show
+formatResult FSL          = show
+formatResult AST          = show . toAST
+formatResult Ternary      = toTernaryString
+formatResult Ascii        = toAscii
+formatResult Decode       = decodeResult
+
+toSimpleT :: String -> String
+toSimpleT s = T.unpack 
+  $ replace "Fork" "t"
+  $ replace "Stem" "t"
+  $ replace "Leaf" "t"
+  $ (T.pack s)
+
+toTernaryString :: T -> String
+toTernaryString Leaf = "0"
+toTernaryString (Stem t) = "1" ++ toTernaryString t
+toTernaryString (Fork t1 t2) = "2" ++ toTernaryString t1 ++ toTernaryString t2
+
+toAST :: T -> TricuAST
+toAST Leaf = TLeaf
+toAST (Stem a) = TStem (toAST a)
+toAST (Fork a b) = TFork (toAST a) (toAST b)
+
 toAscii :: T -> String
 toAscii tree = go tree "" True
   where
@@ -102,41 +152,9 @@ toAscii tree = go tree "" True
         ++ go left (prefix ++ (if isLast then "    " else "|   ")) False
         ++ go right (prefix ++ (if isLast then "    " else "|   ")) True
 
-rules :: IO ()
-rules = putStr $ header
-              ++ (unlines $ tcRules)
-              ++ (unlines $ haskellRules)
-              ++ footer
-  where
-    tcRules :: [String]
-    tcRules =
-      [ "|                                                                               |"
-      , "|                  ┌--------- | Tree Calculus | ---------┐                      |"
-      , "|                  | 1.  t  t      a b       -> a        |                      |"
-      , "|                  | 2.  t (t a)   b c       -> a c (b c)|                      |"
-      , "|                  | 3a. t (t a b) c t       -> a        |                      |"
-      , "|                  | 3b. t (t a b) c (t u)   -> b u      |                      |"
-      , "|                  | 3c. t (t a b) c (t u v) -> c u v    |                      |"
-      , "|                  └-------------------------------------┘                      |"
-      , "|                                                                               |"
-      ]
-    haskellRules :: [String]
-    haskellRules =
-      [ "| ┌------------------------------ | Haskell | --------------------------------┐ |"
-      , "| |                                                                           | |"
-      , "| | data T = Leaf | Stem T | Fork TT                                          | |"
-      , "| |                                                                           | |"
-      , "| | apply :: T -> T -> T                                                      | |"
-      , "| | apply Leaf b                            = Stem b                          | |"
-      , "| | apply (Stem a) b                        = Fork a b                        | |"
-      , "| | apply (Fork Leaf a) _                   = a                               | |"
-      , "| | apply (Fork (Stem a1) a2) b             = apply (apply a1 b) (apply a2 b) | |"
-      , "| | apply (Fork (Fork a1 a2) a3) Leaf       = a1                              | |"
-      , "| | apply (Fork (Fork a1 a2) a3) (Stem u)   = apply a2 u                      | |"
-      , "| | apply (Fork (Fork a1 a2) a3) (Fork u v) = apply (apply a3 u) v            | |"
-      , "| └---------------------------------------------------------------------------┘ |"
-      ]
-    header :: String
-    header = "┌-------------------- | Rules for evaluating Tree Calculus | -------------------┐\n"
-    footer :: String
-    footer = "└-------------------- | Rules for evaluating Tree Calculus | -------------------┘\n"
+decodeResult :: T -> String
+decodeResult tc
+  | Right num  <- toNumber tc = show num
+  | Right str  <- toString tc = "\"" ++ str ++ "\""
+  | Right list <- toList tc   = "[" ++ intercalate ", " (map decodeResult list) ++ "]"
+  | otherwise                 = formatResult TreeCalculus tc

test/Spec.hs

@@ -1,11 +1,15 @@
 module Main where
 
 import Eval
+import FileEval
 import Lexer
-import Library
 import Parser
+import REPL
 import Research
+
 import Control.Exception      (evaluate, try, SomeException)
+import Control.Monad.IO.Class (liftIO)
+import Data.List              (isInfixOf)
 import Test.Tasty
 import Test.Tasty.HUnit
 import Test.Tasty.QuickCheck
@@ -17,304 +21,533 @@ import qualified Data.Set as Set
 main :: IO ()
 main = defaultMain tests
 
-runSapling :: String -> String
-runSapling s = show $ result (evalSapling Map.empty $ parseSapling s)
+runTricu :: String -> String
+runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
 
 tests :: TestTree
-tests = testGroup "Sapling Tests"
-  [ lexerTests
-  , parserTests
-  , integrationTests
-  , evaluationTests
-  , lambdaEvalTests
-  , propertyTests
+tests = testGroup "Tricu Tests"
+  [ lexer
+  , parser
+  , simpleEvaluation
+  , lambdas
+  , baseLibrary
+  , fileEval
+  , modules
+  , demos
   ]
 
-lexerTests :: TestTree
-lexerTests = testGroup "Lexer Tests"
+lexer :: TestTree
+lexer = testGroup "Lexer Tests"
   [ testCase "Lex simple identifiers" $ do
       let input = "x a b = a"
           expect = Right [LIdentifier "x", LIdentifier "a", LIdentifier "b", LAssign, LIdentifier "a"]
-      runParser saplingLexer "" input @?= expect
+      runParser tricuLexer "" input @?= expect
+
   , testCase "Lex Tree Calculus terms" $ do
       let input = "t t t"
           expect = Right [LKeywordT, LKeywordT, LKeywordT]
-      runParser saplingLexer "" input @?= expect
+      runParser tricuLexer "" input @?= expect
+
   , testCase "Lex escaped characters in strings" $ do
       let input = "\"hello\\nworld\""
           expect = Right [LStringLiteral "hello\\nworld"]
-      runParser saplingLexer "" input @?= expect
+      runParser tricuLexer "" input @?= expect
+
   , testCase "Lex mixed literals" $ do
       let input = "t \"string\" 42"
           expect = Right [LKeywordT, LStringLiteral "string", LIntegerLiteral 42]
-      runParser saplingLexer "" input @?= expect
+      runParser tricuLexer "" input @?= expect
+
   , testCase "Lex invalid token" $ do
-      let input = "$invalid"
-      case runParser saplingLexer "" input of
+      let input = "&invalid"
+      case runParser tricuLexer "" input of
         Left _ -> return ()
         Right _ -> assertFailure "Expected lexer to fail on invalid token"
+
   , testCase "Drop trailing whitespace in definitions" $ do
       let input = "x = 5 "
           expect = [LIdentifier "x",LAssign,LIntegerLiteral 5]
-      case (runParser saplingLexer "" input) of
+      case (runParser tricuLexer "" input) of
         Left _ -> assertFailure "Failed to lex input"
         Right i -> i @?= expect
+
   , testCase "Error when using invalid characters in identifiers" $ do
-        case (runParser saplingLexer "" "__result = 5") of
+        case (runParser tricuLexer "" "!result = 5") of
           Left _ -> return ()
-          Right _ -> assertFailure "Expected failure when trying to assign the value of __result"
+          Right _ -> assertFailure "Expected failure when trying to assign the value of !result"
   ]
 
-parserTests :: TestTree
-parserTests = testGroup "Parser Tests"
-  [ --testCase "Error when parsing incomplete definitions" $ do
-    --  let input = lexSapling "x = "
-    --  case (runParser parseExpression "" input) of
-    --    Left _ -> return ()
-    --    Right _ -> assertFailure "Expected failure on invalid input"
-  testCase "Error when assigning a value to T" $ do
-      let input = lexSapling "t = x"
-      case (runParser parseExpression "" input) of
+parser :: TestTree
+parser = testGroup "Parser Tests"
+  [ testCase "Error when assigning a value to T" $ do
+      let tokens = lexTricu "t = x" 
+      case parseSingleExpr tokens of
         Left  _ -> return ()
         Right _ -> assertFailure "Expected failure when trying to assign the value of T"
+
   , testCase "Parse function definitions" $ do
       let input = "x = (\\a b c : a)"
-          expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
+          expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
       parseSingle input @?= expect
+
   , testCase "Parse nested Tree Calculus terms" $ do
       let input = "t (t t) t"
           expect = SApp (SApp TLeaf (SApp TLeaf TLeaf)) TLeaf
       parseSingle input @?= expect
+
   , testCase "Parse sequential Tree Calculus terms" $ do
       let input = "t t t"
           expect = SApp (SApp TLeaf TLeaf) TLeaf
       parseSingle input @?= expect
+
   , testCase "Parse mixed list literals" $ do
       let input = "[t (\"hello\") t]"
           expect = SList [TLeaf, SStr "hello", TLeaf]
       parseSingle input @?= expect
+
   , testCase "Parse function with applications" $ do
       let input  = "f = (\\x : t x)"
-          expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
+          expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
       parseSingle input @?= expect
+
   , testCase "Parse nested lists" $ do
       let input  = "[t [(t t)]]"
           expect = SList [TLeaf,SList [SApp TLeaf TLeaf]]
       parseSingle input @?= expect
+
   , testCase "Parse complex parentheses" $ do
       let input  = "t (t t (t t))"
           expect = SApp TLeaf (SApp (SApp TLeaf TLeaf) (SApp TLeaf TLeaf))
       parseSingle input @?= expect
+
   , testCase "Parse empty list" $ do
       let input  = "[]"
           expect = SList []
       parseSingle input @?= expect
+
   , testCase "Parse multiple nested lists" $ do
       let input  = "[[t t] [t (t t)]]"
           expect = SList [SList [TLeaf,TLeaf],SList [TLeaf,SApp TLeaf TLeaf]]
       parseSingle input @?= expect
+
   , testCase "Parse whitespace variance" $ do
       let input1 = "[t t]"
       let input2 = "[ t t ]"
           expect = SList [TLeaf, TLeaf]
       parseSingle input1 @?= expect
       parseSingle input2 @?= expect
+
   , testCase "Parse string in list" $ do
       let input  = "[(\"hello\")]"
           expect = SList [SStr "hello"]
       parseSingle input @?= expect
+
   , testCase "Parse parentheses inside list" $ do
       let input  = "[t (t t)]"
           expect = SList [TLeaf,SApp TLeaf TLeaf]
       parseSingle input @?= expect
+
   , testCase "Parse nested parentheses in function body" $ do
       let input  = "f = (\\x : t (t (t t)))"
-          expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
+          expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
       parseSingle input @?= expect
+
   , testCase "Parse lambda abstractions" $ do
       let input  = "(\\a : a)"
           expect = (SLambda ["a"] (SVar "a"))
       parseSingle input @?= expect
+
   , testCase "Parse multiple arguments to lambda abstractions" $ do
       let input  = "x = (\\a b : a)"
-          expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
+          expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
       parseSingle input @?= expect
+
   , testCase "Grouping T terms with parentheses in function application" $ do
       let input  = "x = (\\a : a)\nx (t)"
-          expect = [SFunc "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
-      parseSapling input @?= expect
+          expect = [SDef "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
+      parseTricu input @?= expect
+
+  , testCase "Comments 1" $ do
+      let input = "(t) (t) -- (t)"
+          expect = [SApp TLeaf TLeaf]
+      parseTricu input @?= expect
+
+  , testCase "Comments 2" $ do
+      let input = "(t) -- (t) -- (t)"
+          expect = [TLeaf]
+      parseTricu input @?= expect
   ]
 
-integrationTests :: TestTree
-integrationTests = testGroup "Integration Tests"
-  [ testCase "Combine lexer and parser" $ do
-      let input = "x = t t t"
-          expect = SFunc "x" [] (SApp (SApp TLeaf TLeaf) TLeaf)
-      parseSingle input @?= expect
-  , testCase "Complex Tree Calculus expression" $ do
-      let input = "t (t t t) t"
-          expect = SApp (SApp TLeaf (SApp (SApp TLeaf TLeaf) TLeaf)) TLeaf
-      parseSingle input @?= expect
-  ]
-
-evaluationTests :: TestTree
-evaluationTests = testGroup "Evaluation Tests"
+simpleEvaluation :: TestTree
+simpleEvaluation = testGroup "Evaluation Tests"
   [ testCase "Evaluate single Leaf" $ do
       let input = "t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Leaf
+
   , testCase "Evaluate single Stem" $ do
       let input = "t t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Stem Leaf
+
   , testCase "Evaluate single Fork" $ do
       let input = "t t t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Fork Leaf Leaf
+
   , testCase "Evaluate nested Fork and Stem" $ do
       let input = "t (t t) t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Fork (Stem Leaf) Leaf
+
   , testCase "Evaluate `not` function" $ do
       let input = "t (t (t t) (t t t)) t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?=
         Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
+
   , testCase "Environment updates with definitions" $ do
       let input = "x = t\ny = x"
-          env = evalSapling Map.empty (parseSapling input)
+          env = evalTricu Map.empty (parseTricu input)
       Map.lookup "x" env @?= Just Leaf
       Map.lookup "y" env @?= Just Leaf
+
   , testCase "Variable substitution" $ do
       let input = "x = t t\ny = t x\ny"
-          env = evalSapling Map.empty (parseSapling input)
+          env = evalTricu Map.empty (parseTricu input)
       (result env) @?= Stem (Stem Leaf)
+
   , testCase "Multiline input evaluation" $ do
       let input = "x = t\ny = t t\nx"
-          env = evalSapling Map.empty (parseSapling input)
+          env = evalTricu Map.empty (parseTricu input)
       (result env) @?= Leaf
+
   , testCase "Evaluate string literal" $ do
       let input = "\"hello\""
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= ofString "hello"
+
   , testCase "Evaluate list literal" $ do
       let input = "[t (t t)]"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= ofList [Leaf, Stem Leaf]
+
   , testCase "Evaluate empty list" $ do
       let input = "[]"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= ofList []
+
   , testCase "Evaluate variable dependency chain" $ do
       let input = "x = t (t t)\n \
                   \ y = x\n \
                   \ z = y\n \
                   \ variablewithamuchlongername = z\n \
                   \ variablewithamuchlongername"
-          env = evalSapling Map.empty (parseSapling input)
+          env = evalTricu Map.empty (parseTricu input)
       (result env) @?= (Stem (Stem Leaf))
-  , testCase "Evaluate variable shadowing" $ do
+
+
+  , testCase "Immutable definitions" $ do
       let input = "x = t t\nx = t\nx"
-          env = evalSapling Map.empty (parseSapling input)
-      (result env) @?= Leaf
+          env = evalTricu Map.empty (parseTricu input)
+      result <- try (evaluate (runTricu input)) :: IO (Either SomeException String)
+      case result of
+        Left  _ -> return ()
+        Right _ -> assertFailure "Expected evaluation error"
+
+
   , testCase "Apply identity to Boolean Not" $ do
       let not = "(t (t (t t) (t t t)) t)"
       let input = "x = (\\a : a)\nx " ++ not
-          env = evalSapling Map.empty (parseSapling input)
+          env = evalTricu Map.empty (parseTricu input)
       result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
-    , testCase "Constant function matches" $ do
-      let input = "k = (\\a b : a)\nk (t t) t"
-          env = evalSapling Map.empty (parseSapling input)
-      result env @?= Stem Leaf
-   , testCase "Boolean AND_ TF" $ do
-      let input = "and (t t) (t)"
-          env = evalSapling library (parseSapling input)
-      result env @?= Leaf
-   , testCase "Boolean AND_ FT" $ do
-      let input = "and (t) (t t)"
-          env = evalSapling library (parseSapling input)
-      result env @?= Leaf
-   , testCase "Boolean AND_ FF" $ do
-      let input = "and (t) (t)"
-          env = evalSapling library (parseSapling input)
-      result env @?= Leaf
-    , testCase "Boolean AND_ TT" $ do
-      let input = "and (t t) (t t)"
-          env = evalSapling library (parseSapling input)
-      result env @?= Stem Leaf
-    , testCase "Verifying Equality" $ do
-      let input = "equal (t t t) (t t t)"
-          env = evalSapling library (parseSapling input)
-      result env @?= Stem Leaf
   ]
 
-lambdaEvalTests :: TestTree
-lambdaEvalTests = testGroup "Lambda Evaluation Tests"
+lambdas :: TestTree
+lambdas = testGroup "Lambda Evaluation Tests"
   [ testCase "Lambda Identity Function" $ do
       let input = "id = (\\x : x)\nid t"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
   , testCase "Lambda Constant Function (K combinator)" $ do
       let input = "k = (\\x y : x)\nk t (t t)"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
   , testCase "Lambda Application with Variable" $ do
       let input = "id = (\\x : x)\nval = t t\nid val"
-      runSapling input @?= "Stem Leaf"
+      runTricu input @?= "Stem Leaf"
+
   , testCase "Lambda Application with Multiple Arguments" $ do
       let input = "apply = (\\f x y : f x y)\nk = (\\a b : a)\napply k t (t t)"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
    , testCase "Nested Lambda Application" $ do
       let input = "apply = (\\f x y : f x y)\nid = (\\x : x)\napply (\\f x : f x) id t"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
   , testCase "Lambda with a complex body" $ do
       let input = "f = (\\x : t (t x))\nf t"
-      runSapling input @?= "Stem (Stem Leaf)"
+      runTricu input @?= "Stem (Stem Leaf)"
+
   , testCase "Lambda returning a function" $ do
       let input = "f = (\\x : (\\y : x))\ng = f t\ng (t t)"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
   , testCase "Lambda with Shadowing" $ do
       let input = "f = (\\x : (\\x : x))\nf t (t t)"
-      runSapling input @?= "Stem Leaf"
+      runTricu input @?= "Stem Leaf"
+
    , testCase "Lambda returning another lambda" $ do
       let input = "k = (\\x : (\\y : x))\nk_app = k t\nk_app (t t)"
-      runSapling input @?= "Leaf"
+      runTricu input @?= "Leaf"
+
    , testCase "Lambda with free variables" $ do
       let input = "y = t t\nf = (\\x : y)\nf t"
-      runSapling input @?= "Stem Leaf"
+      runTricu input @?= "Stem Leaf"
+
    , testCase "SKI Composition" $ do
       let input = "s = (\\x y z : x z (y z))\nk = (\\x y : x)\ni = (\\x : x)\ncomp = s k i\ncomp t (t t)"
-      runSapling input @?= "Stem (Stem Leaf)"
+      runTricu input @?= "Stem (Stem Leaf)"
+
    , testCase "Lambda with multiple parameters and application" $ do
       let input = "f = (\\a b c : t a b c)\nf t (t t) (t t t)"
-      runSapling input @?= "Stem Leaf"
+      runTricu input @?= "Stem Leaf"
+
    , testCase "Lambda with nested application in the body" $ do
       let input = "f = (\\x : t (t (t x)))\nf t"
-      runSapling input @?= "Stem (Stem (Stem Leaf))"
+      runTricu input @?= "Stem (Stem (Stem Leaf))"
+
     , testCase "Lambda returning a function and applying it" $ do
         let input = "f = (\\x : (\\y : t x y))\ng = f t\ng (t t)"
-        runSapling input @?= "Fork Leaf (Stem Leaf)"
+        runTricu input @?= "Fork Leaf (Stem Leaf)"
+
     , testCase "Lambda applying a variable" $ do
         let input = "id = (\\x : x)\na = t t\nid a"
-        runSapling input @?= "Stem Leaf"
+        runTricu input @?= "Stem Leaf"
+
     , testCase "Nested lambda abstractions in the same expression" $ do
         let input = "f = (\\x : (\\y : x y))\ng = (\\z : z)\nf g t"
-        runSapling input @?= "Leaf"
+        runTricu input @?= "Leaf"
+
   , testCase "Lambda with a string literal" $ do
         let input = "f = (\\x : x)\nf \"hello\""
-        runSapling input @?= "Fork (Fork Leaf (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) Leaf))))"
+        runTricu input @?= "Fork (Fork Leaf (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) Leaf))))"
+
+
    , testCase "Lambda with an integer literal" $ do
         let input = "f = (\\x : x)\nf 42"
-        runSapling input @?= "Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) Leaf)))))"
+        runTricu input @?= "Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) Leaf)))))"
+
    , testCase "Lambda with a list literal" $ do
         let input = "f = (\\x : x)\nf [t (t t)]"
-        runSapling input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+        runTricu input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
   ]
 
-propertyTests :: TestTree
-propertyTests = testGroup "Property Tests"
-  [ testProperty "Lexing and parsing round-trip" $ \input ->
-      case runParser saplingLexer "" input of
-        Left _ -> property True
-        Right tokens -> case runParser parseExpression "" tokens of
-          Left _ -> property True
-          Right ast -> parseSingle input === ast
+baseLibrary :: TestTree
+baseLibrary = testGroup "Library Tests"
+  [ testCase "K combinator 1" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "k (t) (t t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Leaf
+
+  , testCase "K combinator 2" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "k (t t) (t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Stem Leaf
+
+  , testCase "K combinator 3" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "k (t t t) (t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork Leaf Leaf
+
+  , testCase "S combinator" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "s (t) (t) (t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork Leaf (Stem Leaf)
+
+  , testCase "SKK == I (fully expanded)" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "s k k"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork (Stem (Stem Leaf)) (Stem Leaf)
+
+  , testCase "I combinator" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "i not?"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) (Fork Leaf (Fork Leaf Leaf))
+
+  , testCase "Triage test Leaf" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "test t"
+          env = decodeResult $ result $ evalTricu library (parseTricu input)
+      env @?= "\"Leaf\""
+
+  , testCase "Triage test (Stem Leaf)" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "test (t t)"
+          env = decodeResult $ result $ evalTricu library (parseTricu input)
+      env @?= "\"Stem\""
+
+  , testCase "Triage test (Fork Leaf Leaf)" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "test (t t t)"
+          env = decodeResult $ result $ evalTricu library (parseTricu input)
+      env @?= "\"Fork\""
+
+  , testCase "Boolean NOT: true" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "not? true"
+          env = result $ evalTricu library (parseTricu input)
+      env @?= Leaf
+
+  , testCase "Boolean NOT: false" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "not? false"
+          env = result $ evalTricu library (parseTricu input)
+      env @?= Stem Leaf
+
+
+  , testCase "Boolean AND TF" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "and? (t t) (t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Leaf
+
+  , testCase "Boolean AND FT" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "and? (t) (t t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Leaf
+
+  , testCase "Boolean AND FF" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "and? (t) (t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Leaf
+
+  , testCase "Boolean AND TT" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "and? (t t) (t t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Stem Leaf
+
+  , testCase "List head" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "head [(t) (t t) (t t t)]"
+          env = evalTricu library (parseTricu input)
+      result env @?= Leaf
+
+  , testCase "List tail" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "head (tail (tail [(t) (t t) (t t t)]))"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork Leaf Leaf
+
+  , testCase "List map" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "head (tail (map (\\a : (t t t)) [(t) (t) (t)]))"
+          env = evalTricu library (parseTricu input)
+      result env @?= Fork Leaf Leaf
+
+  , testCase "Empty list check" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "emptyList? []"
+          env = evalTricu library (parseTricu input)
+      result env @?= Stem Leaf
+
+  , testCase "Non-empty list check" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "not? (emptyList? [(1) (2) (3)])"
+          env = evalTricu library (parseTricu input)
+      result env @?= Stem Leaf
+
+  , testCase "Concatenate strings" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "lconcat \"Hello, \" \"world!\""
+          env = decodeResult $ result $ evalTricu library (parseTricu input)
+      env @?= "\"Hello, world!\""
+
+  , testCase "Verifying Equality" $ do
+      library <- evaluateFile "./lib/base.tri"
+      let input = "equal? (t t t) (t t t)"
+          env = evalTricu library (parseTricu input)
+      result env @?= Stem Leaf
+  ]
+
+fileEval :: TestTree
+fileEval = testGroup "File evaluation tests"
+  [ testCase "Forks" $ do
+      res <- liftIO $ evaluateFileResult "./test/fork.tri"
+      res @?= Fork Leaf Leaf
+
+  , testCase "File ends with comment" $ do
+      res <- liftIO $ evaluateFileResult "./test/comments-1.tri"
+      res @?= Fork (Stem Leaf) Leaf
+
+  , testCase "Mapping and Equality" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      fEnv    <- liftIO $ evaluateFileWithContext library "./test/map.tri"
+      (mainResult fEnv) @?= Stem Leaf
+
+  , testCase "Eval and decoding string" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res <- liftIO $ evaluateFileWithContext library "./test/string.tri"
+      decodeResult (result res) @?= "\"String test!\""
+  ]
+
+modules :: TestTree
+modules = testGroup "Test modules"
+  [ testCase "Detect cyclic dependencies" $ do
+      result <- try (liftIO $ evaluateFileResult "./test/cycle-1.tri") :: IO (Either SomeException T)
+      case result of
+        Left e -> do
+          let errorMsg = show e
+          if "Encountered cyclic import" `isInfixOf` errorMsg
+            then return ()
+            else assertFailure $ "Unexpected error: " ++ errorMsg
+        Right _ -> assertFailure "Expected cyclic dependencies"
+  , testCase "Module imports and namespacing" $ do
+      res <- liftIO $ evaluateFileResult "./test/namespace-A.tri"
+      res @?= Leaf
+  , testCase "Multiple imports" $ do
+      res <- liftIO $ evaluateFileResult "./test/vars-A.tri"
+      res @?= Leaf
+  , testCase "Error on unresolved variable" $ do
+      result <- try (liftIO $ evaluateFileResult "./test/unresolved-A.tri") :: IO (Either SomeException T)
+      case result of
+        Left e -> do
+          let errorMsg = show e
+          if "undefinedVar" `isInfixOf` errorMsg
+            then return ()
+            else assertFailure $ "Unexpected error: " ++ errorMsg
+        Right _ -> assertFailure "Expected unresolved variable error"
+  , testCase "Multi-level imports" $ do
+      res <- liftIO $ evaluateFileResult "./test/multi-level-A.tri"
+      res @?= Leaf
+  , testCase "Lambda expression namespaces" $ do
+      res <- liftIO $ evaluateFileResult "./test/lambda-A.tri"
+      res @?= Leaf
+  ]
+
+
+-- All of our demo tests are also module tests
+demos :: TestTree
+demos = testGroup "Test provided demo functionality"
+  [ testCase "Structural equality demo" $ do
+      res     <- liftIO $ evaluateFileResult "./demos/equality.tri"
+      decodeResult res @?= "t t"
+  , testCase "Convert values back to source code demo" $ do
+      res     <- liftIO $ evaluateFileResult "./demos/toSource.tri"
+      decodeResult res @?= "\"(t (t (t t) (t t t)) (t t (t t t)))\""
+  , testCase "Determining the size of functions" $ do
+      res     <- liftIO $ evaluateFileResult "./demos/size.tri"
+      decodeResult res @?= "454"
+  , testCase "Level Order Traversal demo" $ do
+      res     <- liftIO $ evaluateFileResult "./demos/levelOrderTraversal.tri"
+      decodeResult res @?= "\"\n1 \n2 3 \n4 5 6 7 \n8 11 10 9 12 \""
   ]

test/ascii.tri

@@ -0,0 +1 @@
+t (t (t (t (t t) (t t t)) t) t t) t

test/assignment.tri

@@ -0,0 +1 @@
+x = t (t t) t

test/comments-1.tri

@@ -0,0 +1,9 @@
+-- This is a tricu comment!
+-- t (t t) (t (t t t))
+-- t (t t t) (t t)
+-- x = (\a : a)
+main = t (t t) t -- Fork (Stem Leaf) Leaf
+-- t t
+-- x
+-- x = (\a : a)
+-- t

test/cycle-1.tri

@@ -0,0 +1,5 @@
+!module Cycle
+
+!import "test/cycle-2.tri" Cycle2
+
+cycle1 = t Cycle2.cycle2

test/cycle-2.tri

@@ -0,0 +1,5 @@
+!module Cycle2
+
+!import "test/cycle-1.tri" Cycle1
+
+cycle2 = t Cycle1.cycle1

test/fork.tri

@@ -0,0 +1 @@
+main = t t t 

test/lambda-A.tri

@@ -0,0 +1,2 @@
+!module A
+main = (\x : x) t

test/map.tri

@@ -0,0 +1,2 @@
+x = map (\i : lconcat "Successfully concatenated " i) [("two strings!")]
+main = equal? x [("Successfully concatenated two strings!")]

test/modules-1.tri

@@ -0,0 +1,5 @@
+!module Test
+
+!import "lib/base.tri" Lib
+
+main = Lib.not? t

test/modules-2.tri

@@ -0,0 +1 @@
+n = t t t

test/multi-level-A.tri

@@ -0,0 +1,3 @@
+!module A
+!import "./test/multi-level-B.tri" B
+main = B.main

test/multi-level-B.tri

@@ -0,0 +1,3 @@
+!module B
+!import "./test/multi-level-C.tri" C
+main = C.val

test/multi-level-C.tri

@@ -0,0 +1,2 @@
+!module C
+val = t

test/namespace-A.tri

@@ -0,0 +1,3 @@
+!module A
+!import "./test/namespace-B.tri" B
+main = B.x

test/namespace-B.tri

@@ -0,0 +1,2 @@
+!module B
+x = t

test/size.tri

@@ -0,0 +1,21 @@
+compose = \f g x : f (g x)
+
+succ = y (\self :
+  triage
+    1
+    t
+    (triage
+      (t (t t))
+      (\_ tail : t t (self tail))
+      t))
+
+size = (\x :
+  (y (\self x :
+    compose succ
+      (triage
+        (\x : x)
+        self
+        (\x y : compose (self x) (self y))
+        x)) x 0))
+
+size size

test/string.tri

@@ -0,0 +1 @@
+head (map (\i : lconcat "String " i) [("test!")])

test/undefined.tri

@@ -0,0 +1 @@
+namedTerm = undefinedForTesting

test/unresolved-A.tri

@@ -0,0 +1,2 @@
+!module A
+main = undefinedVar

test/vars-A.tri

@@ -0,0 +1,7 @@
+!module A
+
+!import "./test/vars-B.tri" B
+
+!import "./test/vars-C.tri" C
+
+main = B.y (C.z)

test/vars-B.tri

@@ -0,0 +1,2 @@
+!module B
+y = \x : x

test/vars-C.tri

@@ -0,0 +1,2 @@
+!module C
+z = t

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
-name:           sapling
-version:        0.4.0
+name:           tricu
+version:        0.12.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
@@ -12,41 +12,45 @@ build-type:     Simple
 extra-source-files:
     README.md
 
-executable sapling
+executable tricu
   main-is: Main.hs
   hs-source-dirs:
       src
   default-extensions:
-      ConstraintKinds
-      DataKinds
-      DeriveGeneric
-      FlexibleContexts
-      FlexibleInstances
-      GeneralizedNewtypeDeriving
+      DeriveDataTypeable
+      LambdaCase
+      MultiWayIf
       OverloadedStrings
-      ScopedTypeVariables
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -optl-pthread -fPIC
   build-depends:
     base >=4.7
+    , cmdargs
     , containers
     , haskeline
     , megaparsec
     , mtl
+    , text
   other-modules:
     Eval
+    FileEval
     Lexer
-    Library
     Parser
     REPL
     Research
   default-language: Haskell2010
 
-test-suite sapling-tests
+test-suite tricu-tests
   type:                exitcode-stdio-1.0
   main-is:             Spec.hs
   hs-source-dirs:      test, src
+  default-extensions:
+      DeriveDataTypeable
+      LambdaCase
+      MultiWayIf
+      OverloadedStrings
   build-depends:       
     base
+    , cmdargs
     , containers
     , haskeline
     , megaparsec
@@ -54,11 +58,12 @@ test-suite sapling-tests
     , tasty
     , tasty-hunit
     , tasty-quickcheck
+    , text
   default-language:    Haskell2010
   other-modules:
     Eval
+    FileEval
     Lexer
-    Library
     Parser
     REPL
     Research