Definition dependency analysis

tricu now allows defining terms in any order and will resolve
dependencies to ensure that they're evaluated in the right order.
Undefined terms are detected and throw errors during dependency
ordering.
For now we can't define top-level mutually recursive terms.

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

@@ -0,0 +1,69 @@
+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: ${{ secrets.REGISTRY_PASSWORD }}
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Build and shrink binary
+        run: |
+          nix build
+          cp -L ./result/bin/tricu ./tricu
+          chmod 755 ./tricu
+          nix develop --command upx ./tricu
+  
+      - name: Setup go for release action
+        uses: actions/setup-go@v5
+        with:
+          go-version: '>=1.20.1'
+  
+      - name: Release binary
+        uses: https://gitea.com/actions/release-action@main
+        with:
+          files: |-
+            ./tricu
+          api_key: '${{ secrets.RELEASE_TOKEN }}'
+          pre_release: 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

@@ -1,18 +1,88 @@
-# sapling
+# tricu
 
-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) .
+## Introduction
 
-It offers a minimal amount of syntax sugar:
+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.
 
-- `t` operator behaving by the rules of Tree Calculus
-- Variable definitions
-- Lambda abstractions
-- List, Integer, and String literals
+tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
-This is an active experimentation project by [someone who has no idea what they're doing](https://eversole.co).
+## Features
+
+- Tree Calculus operator: `t`
+- Assignments: `x = t t`
+- 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)
+- Immutability
+
+## REPL examples
+
+```
+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!"
+
+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
+```
+
+## Installation and Use
+
+[Releases are available for Linux.](https://git.eversole.co/James/tricu/releases)
+
+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).
+                    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 +1,35 @@
+-- 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 = 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?  = equal? true_TC?  true_Lambda?
+bothFalseEqual? = equal? false_TC? false_Lambda?

demos/levelOrderTraversal.tri

@@ -0,0 +1,62 @@
+-- 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 : head node
+
+left = (\node : if (emptyList? node)
+  [] 
+  (if (emptyList? (tail node)) 
+    [] 
+    (head (tail node))))
+
+right = (\node : if (emptyList? node) 
+  [] 
+  (if (emptyList? (tail node)) 
+    [] 
+    (if (emptyList? (tail (tail node))) 
+      [] 
+      (head (tail (tail node))))))
+
+processLevel = y (\self queue : if (emptyList? queue) 
+  [] 
+  (pair (map label queue) (self (filter 
+    (\node : not? (emptyList? node)) 
+      (lconcat (map left queue) (map right queue))))))
+
+levelOrderTraversal_ = \a : processLevel (t a t)
+
+toLineString = y (\self levels : if (emptyList? levels) 
+  "" 
+  (lconcat 
+    (lconcat (map (\x : lconcat x " ") (head levels)) "") 
+    (if (emptyList? (tail levels)) "" (lconcat (t (t 10 t) t) (self (tail levels))))))
+
+levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
+
+flatten = foldl (\acc x : lconcat acc x) ""
+
+levelOrderTraversal = \s : 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]]]
+
+exampleTwo

demos/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

demos/toSource.tri

@@ -0,0 +1,46 @@
+-- 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 (head "t")
+
+-- Stem case
+sourceStem = (\convert : (\a rest :
+  t (head "(")                       -- Start with a left parenthesis "(".
+    (t (head "t")                    -- Add a "t"
+      (t (head " ")                  -- Add a space.
+        (convert a                   -- Recursively convert the argument.
+          (t (head ")") rest))))))   -- Close with ")" and append the rest.
+
+-- Fork case
+sourceFork = (\convert : (\a b rest :
+  t (head "(")                           -- Start with a left parenthesis "(".
+    (t (head "t")                        -- Add a "t"
+      (t (head " ")                      -- Add a space.
+        (convert a                       -- Recursively convert the first arg.
+          (t (head " ")                  -- Add another space.
+            (convert b                   -- Recursively convert the second arg.
+              (t (head ")") rest)))))))) -- Close with ")" and append the rest.
+
+-- Wrapper around triage 
+toSource_ = y (\self arg :
+  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 true -- OUT: "(t t)"
+exampleTwo = toSource 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

@@ -2,139 +2,180 @@ module Eval where
 
 import Parser
 import Research
-import Data.Set (Set)
-import qualified Data.Set as Set
-import Data.List (foldl')
+
+import Data.List (partition)
+import Data.Map  (Map)
 import qualified Data.Map as Map
-import Data.Map (Map)
+import qualified Data.Set as Set
 
-evalSingle :: Map.Map String T -> SaplingAST -> Map.Map String T
-evalSingle env term = case term of
-    SFunc name [] body ->
-        let result = evalAST env body
-        in Map.insert name result env
-    SApp func arg ->
-        let result = apply (evalAST env func) (evalAST env arg)
-        in Map.insert "__result" result env
-    SVar name -> 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
+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 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 -> toString str
-    SInt num -> toNumber num
-    SList elems -> toList (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
 
-result :: Map String T -> T
-result r = case Map.lookup "__result" r of
-    Just a -> a
-    Nothing -> error "No __result field found in provided environment"
+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
 
+    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"
 
-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 (SFunc n vs b) =
-    SFunc n vs (eliminateLambda b)
-eliminateLambda other = other
+    _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)"
 
-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 (SApp f args) = lambdaToT x f
-lambdaToT x body
-    | not (isFree x body) =
-        SApp tK body
-    | otherwise =
-        SApp
-        (SApp tS (lambdaToT x body))
-        tLeaf
-
-tLeaf :: SaplingAST
-tLeaf = TLeaf
-
-freeVars :: SaplingAST -> Set String
-freeVars (SVar v) = Set.singleton v
-freeVars (SInt _) = Set.empty
-freeVars (SStr _) = Set.empty
-freeVars (SList xs) = foldMap freeVars xs
-freeVars (SFunc _ _ b) = freeVars b
-freeVars (SApp f arg) = freeVars f <> freeVars arg
-freeVars TLeaf = Set.empty
-freeVars (TStem t) = freeVars t
-freeVars (TFork l r) = freeVars l <> freeVars r
-freeVars (SLambda vs b) = foldr Set.delete (freeVars b) vs
-
-isFree :: String -> SaplingAST -> Bool
+isFree :: String -> TricuAST -> Bool
 isFree x = Set.member x . freeVars
 
-toAST :: T -> SaplingAST
-toAST Leaf = TLeaf
-toAST (Stem a) = TStem (toAST a)
-toAST (Fork a b) = TFork (toAST a) (toAST b)
+freeVars :: TricuAST -> Set.Set String
+freeVars (SVar    v    ) = Set.singleton v
+freeVars (SInt    _    ) = Set.empty
+freeVars (SStr    _    ) = Set.empty
+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 v b  ) = foldr Set.delete (freeVars b) v
 
-tI :: SaplingAST
-tI = toAST _I
+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
+    graph              = buildDepGraph defsOnly
+    sortedDefs         = sortDeps graph
+    defMap             = Map.fromList [(name, def) | def@(SDef name _ _) <- defsOnly]
+    orderedDefs        = map (\name -> defMap Map.! name) sortedDefs
+    topDefNames        = Set.fromList (Map.keys defMap)
+    envNames           = Set.fromList (Map.keys env)
+    freeVarsDefs       = foldMap (\(SDef _ _ body) -> freeVars body) defsOnly
+    freeVarsOthers     = foldMap freeVars others
+    allFreeVars        = freeVarsDefs <> freeVarsOthers
+    validNames         = topDefNames `Set.union` envNames
+    missingDeps        = Set.toList (allFreeVars `Set.difference` validNames)
 
-tK :: SaplingAST
-tK = toAST _K
+    isDef (SDef _ _ _) = True
+    isDef _            = False
 
-tS :: SaplingAST
-tS = toAST _S
+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 [] (Map.keys graph)
+  where
+    go sorted [] = sorted
+    go sorted remaining
+      | null ready =
+          errorWithoutStackTrace
+            "ERROR: Top-level cyclic dependency detected and prohibited\n\
+           \RESOLVE: Use nested lambdas"
+      | otherwise = go (sorted ++ ready) notReady
+      where
+        ready    = [ name | name <- remaining
+                    , all (`elem` sorted) (Set.toList (graph Map.! name))]
+        notReady =
+          [ name | name <- remaining , name `notElem` ready]
+
+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 -> errorWithoutStackTrace "No __result field found in provided env"

src/FileEval.hs

@@ -0,0 +1,30 @@
+module FileEval where
+
+import Eval
+import Parser
+import Research
+
+import System.IO
+
+import qualified Data.Map as Map
+
+evaluateFileResult :: FilePath -> IO T
+evaluateFileResult filePath = do
+  contents <- readFile filePath
+  let asts = parseTricu contents
+  let finalEnv = evalTricu Map.empty asts
+  case Map.lookup "__result" finalEnv of
+    Just finalResult -> return finalResult
+    Nothing -> errorWithoutStackTrace "No expressions to evaluate found"
+
+evaluateFile :: FilePath -> IO Env
+evaluateFile filePath = do
+  contents <- readFile filePath
+  let asts = parseTricu contents
+  pure $ evalTricu Map.empty asts
+
+evaluateFileWithContext :: Env -> FilePath -> IO Env
+evaluateFileWithContext env filePath = do
+  contents <- readFile filePath
+  let asts = parseTricu contents
+  pure $ evalTricu env asts

src/Lexer.hs

@@ -1,33 +1,28 @@
 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
-  deriving (Show, Eq, Ord)
 
 keywordT :: Lexer LToken
 keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
 
 identifier :: Lexer LToken
 identifier = do
-  name <- some (letterChar <|> char '_' <|> char '-')
+  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)
@@ -41,11 +36,8 @@ 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)
+  char '"' --"
+  return (LStringLiteral content)
 
 assign :: Lexer LToken
 assign = char '=' *> pure LAssign
@@ -72,25 +64,38 @@ lnewline :: Lexer LToken
 lnewline = char '\n' *> pure LNewline
 
 sc :: Lexer ()
-sc = skipMany (char ' ' <|> char '\t')
+sc = space
+  (void $ takeWhile1P (Just "space") (\c -> c == ' ' || c == '\t'))
+  (skipLineComment "--")
+  (skipBlockComment "|-" "-|")
 
-saplingLexer :: Lexer [LToken]
-saplingLexer = many (sc *> choice
-  [ try identifier
-  , try keywordT
-  , try integerLiteral
-  , try stringLiteral
-  , assign
-  , colon
-  , backslash
-  , openParen
-  , closeParen
-  , openBracket
-  , closeBracket
-  , lnewline
-  ] <* sc) <* eof
+tricuLexer :: Lexer [LToken]
+tricuLexer = do
+  sc
+  tokens <- many $ do
+    tok <- choice tricuLexer'
+    sc
+    pure tok
+  sc
+  eof
+  pure tokens
+    where
+      tricuLexer' = 
+        [ try lnewline
+        , try identifier
+        , try keywordT
+        , try integerLiteral
+        , try stringLiteral
+        , assign
+        , colon
+        , backslash
+        , openParen
+        , closeParen
+        , openBracket
+        , closeBracket
+        ]
 
-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/Main.hs

@@ -1,13 +1,87 @@
 module Main where
 
-import Eval
-import Lexer
-import Parser
-import REPL (repl)
+import Eval                   (evalTricu, result)
+import FileEval
+import Parser                 (parseTricu)
+import REPL
 import Research
 
+import Control.Monad          (foldM)
+import Control.Monad.IO.Class (liftIO)
+import Text.Megaparsec        (runParser)
+import System.Console.CmdArgs
+
 import qualified Data.Map as Map
-import Text.Megaparsec (runParser)
+
+data TricuArgs
+  = Repl
+  | Evaluate { file :: [FilePath], form :: EvaluatedForm }
+  | Decode { 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).\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 = Decode
+  { 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 = repl Map.empty --(Map.fromList [("__result", Leaf)])
+main = do
+  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 $ result finalEnv
+      let fRes = formatResult form result
+      putStr fRes
+    Decode { file = filePaths } -> do
+      value <- case filePaths of
+        [] -> getContents
+        (filePath:_) -> readFile filePath
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      putStrLn $ decodeResult $ result $ evalTricu library $ parseTricu value
+
+runTricu :: String -> T
+runTricu input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+   in result finalEnv

src/Parser.hs

@@ -1,254 +1,292 @@
 module Parser where
 
-import Debug.Trace
-
 import Lexer
-import Research hiding (toList)
+import Research
 
-import Control.Exception (throw)
+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 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)
+data PState = PState
+  { parenDepth  :: Int
+  , bracketDepth :: Int
+  } deriving (Show)
 
-parseSapling :: String -> [SaplingAST]
-parseSapling input =
-  let nonEmptyLines = filter (not . null) (lines input)
-  in map parseSingle nonEmptyLines
+type ParserM = StateT PState (Parsec Void [LToken])
 
-parseSingle :: String -> SaplingAST
-parseSingle "" = error "Empty input provided to parseSingle"
-parseSingle input = case runParser parseExpression "" (lexSapling input) of
-  Left  err -> error $ handleParseError err
-  Right ast -> ast
+satisfyM :: (LToken -> Bool) -> ParserM LToken
+satisfyM f = do
+  token <- lift (satisfy f)
+  modify' (updateDepth token)
+  return token
 
-scnParser :: Parser ()
-scnParser = skipMany (satisfy isNewline)
+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
 
-parseExpression :: Parser SaplingAST
-parseExpression = choice
-  [ try parseFunction
-  , try parseLambda
-  , try parseListLiteral
-  , try parseApplication
-  , try parseTreeTerm
-  , parseLiteral
+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
+
+parseProgramM :: ParserM [TricuAST]
+parseProgramM = do
+  skipMany topLevelNewline
+  exprs <- sepEndBy parseOneExpression (some topLevelNewline)
+  skipMany topLevelNewline
+  return exprs
+
+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)
 
-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)
+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
 
-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
-  , 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
-
-parseAtomicBase :: Parser SaplingAST
-parseAtomicBase = choice
-  [ parseVar
-  , parseTreeLeaf
-  , parseGrouped
+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
-
-esNewline        (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

@@ -1,25 +1,68 @@
 module REPL where
 
 import Eval
+import FileEval
 import Lexer
 import Parser
 import Research
 
-import Control.Monad         (void)
-import qualified Data.Map as Map
-import System.IO            (hFlush, stdout)
+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
 
-repl :: Map.Map String T -> IO ()
-repl env = do
-  putStr "sapling > "
-  hFlush stdout
-  input <- getLine
-  if input == "_:exit"
-    then putStrLn "Goodbye!"
-    else do
-      let clearEnv = Map.delete "__result" env
-      let newEnv   = evalSingle clearEnv (parseSingle input)
-      case Map.lookup "__result" newEnv of
-        Just r  -> putStrLn $ "sapling < " ++ show r
-        Nothing -> pure ()
-      repl newEnv
+import qualified Data.Map as Map
+
+repl :: Env -> IO ()
+repl env = runInputT defaultSettings (loop env)
+  where
+    loop :: Env -> InputT IO ()
+    loop env = 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 s  <- minput, strip s == "!load" -> 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
+
+    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
+
+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

src/Research.hs

@@ -1,13 +1,57 @@
 module Research where
 
-import Data.List (intercalate)
 import Control.Monad.State
-import qualified Data.Map as Map
-import Data.Map (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
+  deriving (Show, Eq, Ord)
+
+-- Lexer Tokens
+data LToken
+  = LKeywordT
+  | LIdentifier String
+  | LIntegerLiteral Int
+  | LStringLiteral String
+  | LAssign
+  | LColon
+  | LBackslash
+  | LOpenParen
+  | LCloseParen
+  | LOpenBracket
+  | LCloseBracket
+  | LNewline
+  deriving (Show, Eq, Ord)
+
+-- Output formats
+data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii
+  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
@@ -17,26 +61,6 @@ 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
-
-_I :: T
-_I = apply (apply _S _K) _K -- Fork (Stem (Stem Leaf)) (Stem Leaf)
-
 -- Booleans
 _false :: T
 _false = Leaf
@@ -48,35 +72,67 @@ _not :: T
 _not = Fork (Fork _true (Fork Leaf _false)) Leaf
 
 -- Marshalling
-toString :: String -> T
-toString str = toList (map toNumber (map fromEnum str))
+ofString :: String -> T
+ofString str = ofList (map ofNumber (map fromEnum str))
 
-ofString :: T -> String
-ofString tc = map (toEnum . ofNumber) (ofList tc)
-
-toNumber :: Int -> T
-toNumber 0 = Leaf
-toNumber n =
+ofNumber :: Int -> T
+ofNumber 0 = Leaf
+ofNumber n =
   Fork
     (if odd n then Stem Leaf else Leaf)
-    (toNumber (n `div` 2))
+    (ofNumber (n `div` 2))
 
-ofNumber :: T -> Int
-ofNumber Leaf = 0
-ofNumber (Fork Leaf rest) = 2 * ofNumber rest
-ofNumber (Fork (Stem Leaf) rest) = 1 + 2 * ofNumber rest
-ofNumber _ = error "Invalid Tree Calculus number"
+ofList :: [T] -> T
+ofList [] = Leaf
+ofList (x:xs) = Fork x (ofList xs)
 
-toList :: [T] -> T
-toList [] = Leaf
-toList (x:xs) = Fork x (toList xs)
+toNumber :: T -> Either String Int
+toNumber Leaf = Right 0
+toNumber (Fork Leaf rest) = case toNumber rest of
+  Right n -> Right (2 * n)
+  Left err -> Left err
+toNumber (Fork (Stem Leaf) rest) = case toNumber rest of
+  Right n -> Right (1 + 2 * n)
+  Left err -> Left err
+toNumber _ = Left "Invalid Tree Calculus number"
 
-ofList :: T -> [T]
-ofList Leaf = []
-ofList (Fork x rest) = x : ofList rest
-ofList _ = error "Invalid Tree Calculus list"
+toString :: T -> Either String String
+toString tc = case toList tc of
+  Right list -> traverse (fmap toEnum . toNumber) list
+  Left err -> Left "Invalid Tree Calculus string"
+
+toList :: T -> Either String [T]
+toList Leaf = Right []
+toList (Fork x rest) = case toList rest of
+  Right xs -> Right (x : xs)
+  Left err -> Left err
+toList _ = Left "Invalid Tree Calculus list"
+
+-- Outputs
+formatResult :: EvaluatedForm -> T -> String
+formatResult TreeCalculus = toSimpleT . show
+formatResult FSL          = show
+formatResult AST          = show . toAST
+formatResult Ternary      = toTernaryString
+formatResult Ascii        = toAscii
+
+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)
 
--- Utility
 toAscii :: T -> String
 toAscii tree = go tree "" True
   where
@@ -91,41 +147,4 @@ 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"
+-- Utility

test/Spec.hs

@@ -1,241 +1,518 @@
 module Main where
 
 import Eval
+import FileEval
 import Lexer
 import Parser
+import REPL
 import Research
+
 import Control.Exception (evaluate, try, SomeException)
-import qualified Data.Map as Map
+import Control.Monad.IO.Class (liftIO)
 import Test.Tasty
 import Test.Tasty.HUnit
 import Test.Tasty.QuickCheck
 import Text.Megaparsec (runParser)
 
+import qualified Data.Map as Map
+import qualified Data.Set as Set
+
 main :: IO ()
 main = defaultMain tests
 
+runTricu :: String -> String
+runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
+
 tests :: TestTree
-tests = testGroup "Sapling Tests"
-    [ lexerTests
-    , parserTests
-    , integrationTests
-    , evaluationTests
-    , propertyTests
-    ]
+tests = testGroup "Tricu Tests"
+  [ lexer
+  , parser
+  , simpleEvaluation
+  , lambdas
+  , baseLibrary
+  , fileEval
+  , demos
+  ]
 
-lexerTests :: TestTree
-lexerTests = 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
-    , testCase "Lex Tree Calculus terms" $ do
-        let input = "t t t"
-            expect = Right [LKeywordT, LKeywordT, LKeywordT]
-        runParser saplingLexer "" input @?= expect
-    , testCase "Lex escaped characters in strings" $ do
-        let input = "\"hello\\nworld\""
-            expect = Right [LStringLiteral "hello\\nworld"]
-        runParser saplingLexer "" input @?= expect
-    , testCase "Lex mixed literals" $ do
-        let input = "t \"string\" 42"
-            expect = Right [LKeywordT, LStringLiteral "string", LIntegerLiteral 42]
-        runParser saplingLexer "" input @?= expect
-    , testCase "Lex invalid token" $ do
-        let input = "$invalid"
-        case runParser saplingLexer "" 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
-            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
-            Left _ -> return ()
-            Right _ -> assertFailure "Expected failure when trying to assign the value of __result"
-    ]
+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 tricuLexer "" input @?= expect
 
-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
-            Left _ -> return ()
-            Right _ -> assertFailure "Expected failure when trying to assign the value of T"
-    , testCase "Error when parsing bodyless definitions with arguments" $ do
-        let input = lexSapling "x a b = "
-        case (runParser parseExpression "" input) of
-            Left _ -> return ()
-            Right _ -> assertFailure "Expected failure on invalid input"
-    , testCase "Parse function definitions" $ do
-        let input = "x a b c = a"
-        let expect = SFunc "x" ["a","b","c"] (SVar "a")
-        parseSingle input @?= expect
-    , testCase "Parse nested Tree Calculus terms" $ do
-        let input = "t (t t) t"
-        let expect = SApp (SApp TLeaf (SApp TLeaf TLeaf)) TLeaf
-        parseSingle input @?= expect
-    , testCase "Parse sequential Tree Calculus terms" $ do
-        let input = "t t t"
-        let expect = SApp (SApp TLeaf TLeaf) TLeaf
-        parseSingle input @?= expect
-    , testCase "Parse mixed list literals" $ do
-        let input = "[t (\"hello\") t]"
-        let expect = SList [TLeaf, SStr "hello", TLeaf]
-        parseSingle input @?= expect
-    , testCase "Parse function with applications" $ do
-        let input = "f x = t x"
-        let expect = SFunc "f" ["x"] (SApp TLeaf (SVar "x"))
-        parseSingle input @?= expect
-     , testCase "Parse nested lists" $ do
-        let input = "[t [(t t)]]"
-        let expect = SList [TLeaf,SList [SApp TLeaf TLeaf]]
-        parseSingle input @?= expect
-    , testCase "Parse complex parentheses" $ do
-        let input = "t (t t (t t))"
-        let expect = SApp TLeaf (SApp (SApp TLeaf TLeaf) (SApp TLeaf TLeaf))
-        parseSingle input @?= expect
-    , testCase "Parse empty list" $ do
-        let input = "[]"
-        let expect = SList []
-        parseSingle input @?= expect
-    , testCase "Parse multiple nested lists" $ do
-        let input = "[[t t] [t (t t)]]"
-        let 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 ]"
-        let expect = SList [TLeaf, TLeaf]
-        parseSingle input1 @?= expect
-        parseSingle input2 @?= expect
-    , testCase "Parse string in list" $ do
-        let input = "[(\"hello\")]"
-        let expect = SList [SStr "hello"]
-        parseSingle input @?= expect
-    , testCase "Parse parentheses inside list" $ do
-        let input = "[t (t t)]"
-        let expect = SList [TLeaf,SApp TLeaf TLeaf]
-        parseSingle input @?= expect
-    , testCase "Parse nested parentheses in function body" $ do
-        let input = "f = t (t (t t))"
-        let expect = SFunc "f" [] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf)))
-        parseSingle input @?= expect
-    , testCase "Parse lambda abstractions" $ do
-        let input = "(\\a : a)"
-        let expect = (SLambda ["a"] (SVar "a"))
-        parseSingle input @?= expect
-    , testCase "Parse multiple arguments to lambda abstractions" $ do
-        let input = "x = (\\a b : a)"
-        let expect = SFunc "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)\n" <> "x (t)"
-            expect = [SFunc "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
-        parseSapling input @?= expect
-    ]
+  , testCase "Lex Tree Calculus terms" $ do
+      let input = "t t t"
+          expect = Right [LKeywordT, LKeywordT, LKeywordT]
+      runParser tricuLexer "" input @?= expect
 
-integrationTests :: TestTree
-integrationTests = testGroup "Integration Tests"
-    [ testCase "Combine lexer and parser" $ do
-        let input = "x = t t t"
-        let expect = SFunc "x" [] (SApp (SApp TLeaf TLeaf) TLeaf)
-        parseSingle input @?= expect
-    , testCase "Complex Tree Calculus expression" $ do
-        let input = "t (t t t) t"
-        let expect = SApp (SApp TLeaf (SApp (SApp TLeaf TLeaf) TLeaf)) TLeaf
-        parseSingle input @?= expect
-    ]
+  , testCase "Lex escaped characters in strings" $ do
+      let input = "\"hello\\nworld\""
+          expect = Right [LStringLiteral "hello\\nworld"]
+      runParser tricuLexer "" input @?= expect
 
-evaluationTests :: TestTree
-evaluationTests = 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"
-        let env = evalSapling Map.empty (parseSapling 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"
-        let env = evalSapling Map.empty (parseSapling input)
-        (result env) @?= Stem (Stem Leaf)
-     , testCase "Multiline input evaluation" $ do
-        let input = "x = t\ny = t t\nx"
-        let env = evalSapling Map.empty (parseSapling input)
-        (result env) @?= Leaf
-     , testCase "Evaluate string literal" $ do
-        let input = "\"hello\""
-        let ast = parseSingle input
-        (result $ evalSingle Map.empty ast) @?= toString "hello"
-    , testCase "Evaluate list literal" $ do
-        let input = "[t (t t)]"
-        let ast = parseSingle input
-        (result $ evalSingle Map.empty ast) @?= toList [Leaf, Stem Leaf]
-    , testCase "Evaluate empty list" $ do
-        let input = "[]"
-        let ast = parseSingle input
-        (result $ evalSingle Map.empty ast) @?= toList []
-    , testCase "Evaluate variable dependency chain" $ do
-        let input = "x = t (t t)\n \
-                    \ y = x\n \
-                    \ z = y\n \
-                    \ variablewithamuchlongername = z\n \
-                    \ variablewithamuchlongername"
-        let env = evalSapling Map.empty (parseSapling input)
-        (result env) @?= (Stem (Stem Leaf))
-    , testCase "Evaluate variable shadowing" $ do
-        let input = "x = t t\nx = t\nx"
-        let env = evalSapling Map.empty (parseSapling input)
-        (result env) @?= Leaf
-    , testCase "Lambda identity" $ do
-        let input = "(\\a : a)"
-            env = evalSapling Map.empty (parseSapling input)
-        result env @?= Fork (Stem (Stem Leaf)) (Stem Leaf)
-    , testCase "Apply identity to Boolean Not" $ do
-        let not = "(t (t (t t) (t t t)) t)"
-            input = "x = (\\a : a)\nx " ++ not
-            env = evalSapling Map.empty (parseSapling 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 "Lex mixed literals" $ do
+      let input = "t \"string\" 42"
+          expect = Right [LKeywordT, LStringLiteral "string", LIntegerLiteral 42]
+      runParser tricuLexer "" input @?= expect
 
-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
-    ]
+  , testCase "Lex invalid token" $ do
+      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 tricuLexer "" input) of
+        Left _ -> assertFailure "Failed to lex input"
+        Right i -> i @?= expect
+
+  , testCase "Error when using invalid characters in identifiers" $ do
+        case (runParser tricuLexer "" "__result = 5") of
+          Left _ -> return ()
+          Right _ -> assertFailure "Expected failure when trying to assign the value of __result"
+  ]
+
+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 = 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 = 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 = 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 = 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 = [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
+  ]
+
+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 = 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 = evalTricu Map.empty (parseTricu input)
+      (result env) @?= Stem (Stem Leaf)
+
+  , testCase "Multiline input evaluation" $ do
+      let input = "x = t\ny = t t\nx"
+          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 = evalTricu Map.empty (parseTricu input)
+      (result env) @?= (Stem (Stem Leaf))
+
+
+  , testCase "Immutable definitions" $ do
+      let input = "x = t t\nx = t\nx"
+          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 = evalTricu Map.empty (parseTricu input)
+      result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
+  ]
+
+lambdas :: TestTree
+lambdas = testGroup "Lambda Evaluation Tests"
+  [ testCase "Lambda Identity Function" $ do
+      let input = "id = (\\x : x)\nid t"
+      runTricu input @?= "Leaf"
+
+  , testCase "Lambda Constant Function (K combinator)" $ do
+      let input = "k = (\\x y : x)\nk t (t t)"
+      runTricu input @?= "Leaf"
+
+  , testCase "Lambda Application with Variable" $ do
+      let input = "id = (\\x : x)\nval = t t\nid val"
+      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)"
+      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"
+      runTricu input @?= "Leaf"
+
+  , testCase "Lambda with a complex body" $ do
+      let input = "f = (\\x : t (t x))\nf t"
+      runTricu input @?= "Stem (Stem Leaf)"
+
+  , testCase "Lambda returning a function" $ do
+      let input = "f = (\\x : (\\y : x))\ng = f t\ng (t t)"
+      runTricu input @?= "Leaf"
+
+  , testCase "Lambda with Shadowing" $ do
+      let input = "f = (\\x : (\\x : x))\nf t (t t)"
+      runTricu input @?= "Stem Leaf"
+
+   , testCase "Lambda returning another lambda" $ do
+      let input = "k = (\\x : (\\y : x))\nk_app = k t\nk_app (t t)"
+      runTricu input @?= "Leaf"
+
+   , testCase "Lambda with free variables" $ do
+      let input = "y = t t\nf = (\\x : y)\nf t"
+      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)"
+      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)"
+      runTricu input @?= "Stem Leaf"
+
+   , testCase "Lambda with nested application in the body" $ do
+      let input = "f = (\\x : t (t (t x)))\nf t"
+      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)"
+        runTricu input @?= "Fork Leaf (Stem Leaf)"
+
+    , testCase "Lambda applying a variable" $ do
+        let input = "id = (\\x : x)\na = t t\nid a"
+        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"
+        runTricu input @?= "Leaf"
+
+  , testCase "Lambda with a string literal" $ do
+        let input = "f = (\\x : x)\nf \"hello\""
+        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"
+        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)]"
+        runTricu input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+  ]
+
+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
+      res <- liftIO $ evaluateFileResult "./test/map.tri"
+      res @?= 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!\""
+  ]
+
+demos :: TestTree
+demos = testGroup "Test provided demo functionality"
+  [ testCase "Structural equality demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/equality.tri"
+      decodeResult (result res) @?= "t t"
+  , testCase "Convert values back to source code demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/toSource.tri"
+      decodeResult (result res) @?= "\"(t (t (t t) (t t t)) (t t (t t t)))\""
+  , testCase "Determining the size of functions" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/size.tri"
+      decodeResult (result res) @?= "454"
+  , testCase "Level Order Traversal demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/levelOrderTraversal.tri"
+      decodeResult (result 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)
+t (t t) t -- Fork (Stem Leaf) Leaf
+-- t t
+-- x
+-- x = (\a : a)
+-- t

test/fork.tri

@@ -0,0 +1 @@
+t t t 

test/map.tri

@@ -0,0 +1,24 @@
+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)
+yi = (\i : b m (c b (i m)))
+y = yi iC
+triage = (\a b c : t (t a b) c)
+pair = t
+matchList = (\oe oc : triage oe _ oc)
+lconcat = y (\self : matchList (\k : k) (\h r k : pair h (self r k)))
+hmap = y (\self : matchList (\f : t) (\hd tl f : pair (f hd) (self tl f)))
+map = (\f l : hmap l f)
+lAnd = triage (\x : false) (\_ x : x) (\_ _ x : x)
+lOr = triage (\x : x) (\_ _ : true) (\_ _ x : true)
+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))))
+
+x = map (\i : lconcat "Successfully concatenated " i) [("two strings!")]
+equal x [("Successfully concatenated two strings!")]

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

tricu.cabal

@@ -1,8 +1,8 @@
 cabal-version: 1.12
 
-name:           sapling
-version:        0.2.0
-description:    Tree Calculus experiment repository
+name:           tricu
+version:        0.10.0
+description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
 copyright:      James Eversole
@@ -12,48 +12,57 @@ 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
     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
     , mtl
     , tasty
     , tasty-hunit
     , tasty-quickcheck
+    , text
   default-language:    Haskell2010
   other-modules:
     Eval
+    FileEval
     Lexer
     Parser
     REPL