Eval optimization! Tests for demos

Adds support for several special characters in identifiers. Adds a demo
for converting values to source code and another for checking equality.
Updates the existing demo and tests to reflect new names for functions
returning booleans.

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

@@ -1,86 +1,69 @@
-name: Test and Build
+name: Test, Build, and Release
 
-on:
+on: 
   push:
-    branches:
-      - main
-  pull_request:
-    types:
-      - opened
-      - synchronize
+    tags:
+      - '*'
 
 jobs:
   test:
     container:
-      image: docker.matri.cx/nix-runner:latest
+      image: docker.matri.cx/nix-runner:v0.1.0
       credentials:
         username: ${{ secrets.REGISTRY_USERNAME }}
         password: ${{ secrets.REGISTRY_PASSWORD }}
     steps:
-      - name: Checkout code
-        uses: actions/checkout@v3
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
 
       - name: Set up cache for Cabal
         uses: actions/cache@v4
         with:
           path: |
-            ~/.cabal
-            ~/.ghc
-          key: cabal-${{ runner.os }}-${{ hashFiles('tricu.cabal') }}
+            ~/.cache/cabal
+            ~/.config/cabal
+            ~/.local/state/cabal
+          key: cabal-${{ hashFiles('tricu.cabal') }}
           restore-keys: |
-            cabal-${{ runner.os }}-
-
-      - name: Set up cache for Nix
-        uses: actions/cache@v4
-        with:
-          path: |
-            /nix/store
-            /nix/var/nix/cache
-          key: nix-${{ runner.os }}-${{ hashFiles('flake.lock') }}
-          restore-keys: |
-            nix-${{ runner.os }}-
+            cabal-
 
       - name: Initialize Cabal and update package list
         run: |
           nix develop --command cabal update
 
-      - name: Install dependencies and run tests
+      - name: Run test suite
         run: |
           nix develop --command cabal test
 
   build:
     needs: test
     container:
-      image: docker.matri.cx/nix-runner:latest
+      image: docker.matri.cx/nix-runner:v0.1.0
       credentials:
         username: ${{ secrets.REGISTRY_USERNAME }}
         password: ${{ secrets.REGISTRY_PASSWORD }}
     steps:
-      - name: Checkout code
-        uses: actions/checkout@v3
-
-      - name: Set up cache for Cabal
-        uses: actions/cache@v4
+      - uses: actions/checkout@v3
         with:
-          path: |
-            ~/.cabal
-            ~/.ghc
-          key: cabal-${{ runner.os }}-${{ hashFiles('tricu.cabal') }}
-          restore-keys: |
-            cabal-${{ runner.os }}-
+          fetch-depth: 0
 
-      - name: Set up cache for Nix
-        uses: actions/cache@v4
-        with:
-          path: |
-            /nix/store
-            /nix/var/nix/cache
-          key: nix-${{ runner.os }}-${{ hashFiles('flake.lock') }}
-          restore-keys: |
-            nix-${{ runner.os }}-
-
-      - name: Build binary
+      - name: Build and shrink binary
         run: |
           nix build
-          ls -alh ./result/bin/tricu
-
+          cp -L ./result/bin/tricu ./tricu
+          chmod 755 ./tricu
+          nix develop --command upx ./tricu
+  
+      - name: Setup go for release action
+        uses: actions/setup-go@v5
+        with:
+          go-version: '>=1.20.1'
+  
+      - name: Release binary
+        uses: https://gitea.com/actions/release-action@main
+        with:
+          files: |-
+            ./tricu
+          api_key: '${{ secrets.RELEASE_TOKEN }}'
+          pre_release: true

README.md

@@ -2,21 +2,22 @@
 
 ## Introduction
 
-tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. [I'm](https://eversole.co) developing tricu to further research the possibilities offered by the various forms of [Tree Calculi](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf).
+tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) terms, but minimal syntax sugar is included to provide a useful programming tool. 
 
-tricu offers minimal syntax sugar yet manages to provide a complete, intuitive, and familiar programming environment. There is great power in simplicity. tricu offers:
+tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
-1. `t` operator behaving by the rules of Tree Calculus
-1. Function definitions/assignments
-1. Lambda abstractions eliminated to Tree Calculus forms
-1. List, Number, and String literals
-1. Parentheses for grouping function application
+## Features
 
-These features move us cleanly out of the [turing tarpit](https://en.wikipedia.org/wiki/Turing_tarpit) territory that you may find yourself in if you try working only with the `t` operator.
+- 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
 
-tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`. This project was named "sapling" until I discovered the name is already being used for other (completely unrelated) programming language development projects.
-
-## What does it look like?
+## REPL examples
 
 ```
 tricu < -- Anything after `--` on a single line is a comment
@@ -26,19 +27,24 @@ 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.
+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 < test (t t)
 tricu > "Stem"
-tricu < -- We can even write a function to convert a function to source code
-tricu < toTString id
-tricu > "t (t (t t)) t"
+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
 
-You can easily build and/or run this project using [Nix](https://nixos.org/download/).
+[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`
@@ -79,4 +85,4 @@ tricu decode [OPTIONS]
 
 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 tricu 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/LevelOrderTraversal.tri

@@ -1,63 +0,0 @@
--- Level Order Traversal of a labelled binary tree
--- Objective: Print each "level" of the tree on a separate line
---
--- NOTICE: This demo relies on tricu base library functions
--- 
--- We model labelled binary trees as sublists where values act as labels. We
--- require explicit notation of empty nodes. Empty nodes can be represented 
--- with an empty list, `[]`, which is equivalent 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
---
-
-isLeaf = (\node : 
-  lOr 
-    (emptyList node) 
-    (emptyList (tail node)))
-
-getLabel = (\node : head node)
-
-getLeft  = (\node : if (emptyList node) 
-  [] 
-  (if (emptyList (tail node)) 
-    [] 
-    (head (tail node))))
-
-getRight = (\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 getLabel queue) (self (filter 
-    (\node : not (emptyList node)) 
-      (lconcat (map getLeft queue) (map getRight 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) ""
-flatLOT = (\s : lconcat (t 10 t) (flatten (levelOrderToString s)))
-
-exampleOne = flatLOT [("1") [("2") [("4") t t] t] [("3") [("5") t t] [("6") t t]]]
-exampleTwo = flatLOT [("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]]]
-
-exampleOne

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 +1,65 @@
+-- Level Order Traversal of a labelled binary tree
+-- Objective: Print each "level" of the tree on a separate line
+--
+-- NOTICE: This demo relies on tricu base library functions
+-- 
+-- We model labelled binary trees as sublists where values act as labels. We
+-- require explicit not?ation of empty nodes. Empty nodes can be represented 
+-- with an empty list, `[]`, which is equivalent 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

@@ -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

@@ -1,22 +1,25 @@
 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)
-iC = (\a b c : s a (k c) b)
-iD = b (b iC) iC
-iE = b (b iD) iC
-yi = (\i : b m (c b (i m)))
-y = yi iC
-yC = yi iD
-yD = yi iE
-id = (\a : a)
-triage = (\a b c : t (t a b) c)
-pair = t
+_     = 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)
+iC    = (\a b c : s a (k c) b)
+iD    = b (b iC) iC
+iE    = b (b iD) iC
+yi    = (\i : b m (c b (i m)))
+y     = yi iC
+yC    = yi iD
+yD    = yi iE
+id    = (\a : a)
+pair  = t
+if    = (\cond then else : t (t else (t t then)) t cond)
+
+triage = (\leaf stem fork : t (t leaf stem) fork)
+test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
 
 matchBool = (\ot of : triage 
   of 
@@ -36,58 +39,58 @@ matchPair = (\op : triage
   op
 )
 
-not = matchBool false true
-and = matchBool id (\z : false)
-if = (\cond then else : t (t else (t t then)) t cond)
-test = triage "Leaf" (\z : "Stem") (\a b : "Fork")
+not? = matchBool false true
+and? = matchBool id (\_ : false)
+emptyList? = matchList true (\_ _ : false)
 
-emptyList = matchList true (\y z : false)
-head = matchList t (\hd tl : hd)
-tail = matchList t (\hd tl : tl)
+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 
-  (\x : false) 
-  (\_ x : x) 
+  (\_     : false) 
+  (\_ x   : x) 
   (\_ _ x : x)
 )
 
 lOr = (triage 
-  (\x : x) 
-  (\_ _ : true) 
-  (\_ _ x : true)
+  (\x     : x) 
+  (\_ _   : true) 
+  (\_ _ _ : true)
 )
 
-hmap = y (\self : 
+map_ = y (\self : 
   matchList 
-    (\f : t) 
-    (\hd tl f : pair 
-                  (f hd) 
-                  (self tl f)))
-map = (\f l : hmap l f)
+    (\_ : t) 
+    (\head tail f : pair (f head) (self tail f)))
+map = (\f l : map_ l f)
 
-equal = y (\self : triage 
+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))))
+    (\_   : false) 
+    (\_ _ : false)) 
+  (\ax : 
+    triage 
+      false 
+      (self ax) 
+      (\_ _ : false)) 
+  (\ax ay : 
+    triage 
+      false 
+      (\_ : false) 
+      (\bx by : lAnd (self ax bx) (self ay by))))
 
-hfilter = y (\self : matchList (\f : t) (\hd tl f : matchBool (t hd) i (f hd) (self tl f)))
-filter  = (\f l : hfilter l f)
+filter_ = y (\self : matchList 
+  (\_ : t) 
+  (\head tail f : matchBool (t head) i (f head) (self tail f)))
+filter  = (\f l : filter_ l f)
 
-hfoldl  = y (\self f l x : matchList (\acc : acc) (\hd tl acc : self f tl (f acc hd)) l x)
-foldl   = (\f x l : hfoldl f l x)
+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)
 
-hfoldr  = y (\self x f l : matchList x (\hd tl : f (self x f tl) hd) l)
-foldr   = (\f x l : hfoldr x f l)
+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)

src/Eval.hs

@@ -11,15 +11,20 @@ import qualified Data.Set as Set
 evalSingle :: Env -> TricuAST -> Env
 evalSingle env term
   | SFunc name [] body <- term =
-      let res = evalAST env body
-      in Map.insert "__result" res (Map.insert name res env)
+      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"
+        Nothing -> errorWithoutStackTrace $ "Variable `" ++ name ++ "` not defined"
   | otherwise =
       Map.insert "__result" (evalAST env term) env
 
@@ -54,11 +59,13 @@ evalAST env term
 elimLambda :: TricuAST -> TricuAST
 elimLambda = go
   where
+    go (SLambda [v] (SApp f (SVar x)))
+      | v == x && not (isFree v f) = elimLambda f
     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
+      | 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
@@ -68,7 +75,6 @@ elimLambda = go
       | otherwise        = SApp (SApp _S (toSKI x n)) (toSKI x u)
     toSKI x t
       | not (isFree x t) = SApp _K t
-      | otherwise        = SApp (SApp _S (toSKI x t)) TLeaf
 
     _S = parseSingle "t (t (t t t)) t"
     _K = parseSingle "t t"

src/Lexer.hs

@@ -18,7 +18,10 @@ keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
 identifier :: Lexer LToken
 identifier = do
   first <- letterChar <|> char '_'
-  rest <- many (letterChar <|> char '_' <|> char '-' <|> digitChar)
+  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"

src/Parser.hs

@@ -12,7 +12,8 @@ import Text.Megaparsec.Error (ParseErrorBundle, errorBundlePretty)
 import qualified Data.Set as Set
 
 data PState = PState
-  { depth :: Int
+  { parenDepth  :: Int
+  , bracketDepth :: Int
   } deriving (Show)
 
 type ParserM = StateT PState (Parsec Void [LToken])
@@ -24,24 +25,33 @@ satisfyM f = do
   return token
 
 updateDepth :: LToken -> PState -> PState
-updateDepth LOpenParen  st = st { depth = depth st + 1 }
-updateDepth LCloseParen st = st { depth = max 0 (depth st - 1) }
-updateDepth _           st = st
+updateDepth LOpenParen    st = st { parenDepth   = parenDepth st   + 1 }
+updateDepth LOpenBracket  st = st { bracketDepth = bracketDepth st + 1 }
+updateDepth LCloseParen   st = st { parenDepth   = parenDepth st   - 1 }
+updateDepth LCloseBracket st = st { bracketDepth = bracketDepth st - 1 }
+updateDepth _ st = st
 
 topLevelNewline :: ParserM ()
 topLevelNewline = do
   st <- get
-  if depth st == 0
+  if parenDepth st == 0 && bracketDepth st == 0
     then void (satisfyM (== LNewline))
-    else fail "Top-level exit in paren context"
+    else fail "Top-level exit in nested context (paren or bracket)"
 
 parseProgram :: [LToken] -> Either (ParseErrorBundle [LToken] Void) [TricuAST]
 parseProgram tokens =
-  runParser (evalStateT parseProgramM (PState 0)) "" tokens
+  runParser (evalStateT (parseProgramM <* finalizeDepth <* eof) (PState 0 0)) "" tokens
 
 parseSingleExpr :: [LToken] -> Either (ParseErrorBundle [LToken] Void) TricuAST
 parseSingleExpr tokens =
-  runParser (evalStateT (scnParserM *> parseExpressionM <* eofM) (PState 0)) "" 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 =
@@ -49,7 +59,7 @@ parseTricu input =
     [] -> []
     toks ->
       case parseProgram toks of
-        Left err   -> error (handleParseError err)
+        Left err   -> errorWithoutStackTrace (handleParseError err)
         Right asts -> asts
 
 parseSingle :: String -> TricuAST
@@ -58,7 +68,7 @@ parseSingle input =
     [] -> SEmpty
     toks ->
       case parseSingleExpr toks of
-        Left err -> error (handleParseError err)
+        Left err -> errorWithoutStackTrace (handleParseError err)
         Right ast -> ast
 
 parseProgramM :: ParserM [TricuAST]
@@ -73,12 +83,15 @@ parseOneExpression = scnParserM *> parseExpressionM
 
 scnParserM :: ParserM ()
 scnParserM = skipMany $ do
-  t <- lookAhead anySingle
+  t  <- lookAhead anySingle
   st <- get
-  if depth st > 0 && isNewline t
-    then void (satisfyM isNewline)
-    else
-      fail "In paren context or no space token" <|> empty
+  if | (parenDepth st > 0 || bracketDepth st > 0) && case t of
+         LNewline -> True
+         _        -> False -> void $ satisfyM $ \case
+           LNewline -> True
+           _        -> False
+     | otherwise -> fail "In nested context or no space token" <|> empty
+
 
 eofM :: ParserM ()
 eofM = lift eof
@@ -96,23 +109,32 @@ parseExpressionM = choice
 
 parseFunctionM :: ParserM TricuAST
 parseFunctionM = do
-  LIdentifier name <- satisfyM isIdentifier
-  args <- many (satisfyM isIdentifier)
+  LIdentifier name <- satisfyM $ \case
+    LIdentifier _ -> True
+    _             -> False
+  args <- many $ satisfyM $ \case
+    LIdentifier _ -> True
+    _             -> False
   _    <- satisfyM (== LAssign)
   scnParserM
   body <- parseExpressionM
   pure (SFunc name (map getIdentifier args) body)
 
 parseLambdaM :: ParserM TricuAST
-parseLambdaM = between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) $ do
-  _       <- satisfyM (== LBackslash)
-  param   <- satisfyM isIdentifier
-  rest    <- many (satisfyM isIdentifier)
-  _       <- satisfyM (== LColon)
-  scnParserM
-  body    <- parseLambdaExpressionM
-  let nested = foldr (\v acc -> SLambda [getIdentifier v] acc) body rest
-  pure (SLambda [getIdentifier param] nested)
+parseLambdaM =
+  between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) $ do
+    _     <- satisfyM (== LBackslash)
+    param <- satisfyM $ \case
+      LIdentifier _ -> True
+      _             -> False
+    rest  <- many $ satisfyM $ \case
+      LIdentifier _ -> True
+      _             -> False
+    _     <- satisfyM (== LColon)
+    scnParserM
+    body <- parseLambdaExpressionM
+    let nested = foldr (\v acc -> SLambda [getIdentifier v] acc) body rest
+    pure (SLambda [getIdentifier param] nested)
 
 parseLambdaExpressionM :: ParserM TricuAST
 parseLambdaExpressionM = choice
@@ -158,8 +180,10 @@ parseAtomicBaseM = choice
 
 parseTreeLeafM :: ParserM TricuAST
 parseTreeLeafM = do
-  _ <- satisfyM isKeywordT
-  notFollowedBy (lift (satisfy (== LAssign)))
+  _ <- satisfyM $ \case
+    LKeywordT -> True
+    _         -> False
+  notFollowedBy $ lift $ satisfy (== LAssign)
   pure TLeaf
 
 parseTreeTermM :: ParserM TricuAST
@@ -201,7 +225,10 @@ parseLiteralM = choice
 parseListLiteralM :: ParserM TricuAST
 parseListLiteralM = do
   _        <- satisfyM (== LOpenBracket)
-  elements <- many parseListItemM
+  elements <- many $ do
+    scnParserM
+    parseListItemM
+  scnParserM
   _        <- satisfyM (== LCloseBracket)
   pure (SList elements)
 
@@ -221,7 +248,10 @@ parseGroupedItemM = do
 
 parseSingleItemM :: ParserM TricuAST
 parseSingleItemM = do
-  token <- satisfyM isListItem
+  token <- satisfyM $ \case
+    LIdentifier _ -> True
+    LKeywordT     -> True
+    _             -> False
   case token of
     LIdentifier name -> pure (SVar name)
     LKeywordT        -> pure TLeaf
@@ -229,71 +259,46 @@ parseSingleItemM = do
 
 parseVarM :: ParserM TricuAST
 parseVarM = do
-  LIdentifier name <- satisfyM isIdentifier
+  LIdentifier name <- satisfyM $ \case
+    LIdentifier _ -> True
+    _             -> False
   if name == "t" || name == "__result"
     then fail ("Reserved keyword: " ++ name ++ " cannot be assigned.")
     else pure (SVar name)
 
 parseIntLiteralM :: ParserM TricuAST
 parseIntLiteralM = do
-  LIntegerLiteral value <- satisfyM isIntegerLiteral
+  LIntegerLiteral value <- satisfyM $ \case
+    LIntegerLiteral _ -> True
+    _                 -> False
   pure (SInt value)
 
 parseStrLiteralM :: ParserM TricuAST
 parseStrLiteralM = do
-  LStringLiteral value <- satisfyM isStringLiteral
+  LStringLiteral value <- satisfyM $ \case 
+    LStringLiteral _ -> True
+    _ -> False
   pure (SStr value)
 
-isKeywordT :: LToken -> Bool
-isKeywordT LKeywordT = True
-isKeywordT _         = False
-
-isIdentifier :: LToken -> Bool
-isIdentifier (LIdentifier _) = True
-isIdentifier _               = False
-
-isIntegerLiteral :: LToken -> Bool
-isIntegerLiteral (LIntegerLiteral _) = True
-isIntegerLiteral _                   = False
-
-isStringLiteral :: LToken -> Bool
-isStringLiteral (LStringLiteral _)   = True
-isStringLiteral _                    = False
-
-isLiteral :: LToken -> Bool
-isLiteral (LIntegerLiteral _) = True
-isLiteral (LStringLiteral _)  = True
-isLiteral _                   = False
-
-isListItem :: LToken -> Bool
-isListItem (LIdentifier _) = True
-isListItem LKeywordT       = True
-isListItem _               = False
-
-isNewline :: LToken -> Bool
-isNewline LNewline = True
-isNewline _        = False
-
 getIdentifier :: LToken -> String
 getIdentifier (LIdentifier name) = name
-getIdentifier _                  = error "Expected identifier"
+getIdentifier _                  = errorWithoutStackTrace "Expected identifier"
 
 handleParseError :: ParseErrorBundle [LToken] Void -> String
 handleParseError bundle =
-  let errors        = bundleErrors bundle
-      errorList     = Data.List.NonEmpty.toList errors
-      formattedErrs = map showError errorList
-  in unlines ("Parse error(s) encountered:" : formattedErrs)
-
-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)
+  let errors = bundleErrors bundle
+      formattedErrors = map formatError (Data.List.NonEmpty.toList errors)
+  in unlines ("Parse error(s) encountered:" : formattedErrors)
 
+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"

test/Spec.hs

@@ -25,180 +25,216 @@ runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
 
 tests :: TestTree
 tests = testGroup "Tricu Tests"
-  [ lexerTests
-  , parserTests
-  , evaluationTests
-  , lambdaEvalTests
-  , libraryTests
-  , fileEvaluationTests
+  [ lexer
+  , parser
+  , simpleEvaluation
+  , lambdas
+  , baseLibrary
+  , fileEval
+  , demos
   ]
 
-lexerTests :: TestTree
-lexerTests = testGroup "Lexer Tests"
+lexer :: TestTree
+lexer = testGroup "Lexer Tests"
   [ testCase "Lex simple identifiers" $ do
       let input = "x a b = a"
           expect = Right [LIdentifier "x", LIdentifier "a", LIdentifier "b", LAssign, LIdentifier "a"]
       runParser tricuLexer "" input @?= expect
+
   , testCase "Lex Tree Calculus terms" $ do
       let input = "t t t"
           expect = Right [LKeywordT, LKeywordT, LKeywordT]
       runParser tricuLexer "" input @?= expect
+
   , testCase "Lex escaped characters in strings" $ do
       let input = "\"hello\\nworld\""
           expect = Right [LStringLiteral "hello\\nworld"]
       runParser tricuLexer "" input @?= expect
+
   , testCase "Lex mixed literals" $ do
       let input = "t \"string\" 42"
           expect = Right [LKeywordT, LStringLiteral "string", LIntegerLiteral 42]
       runParser tricuLexer "" input @?= expect
+
   , 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"
   ]
 
-parserTests :: TestTree
-parserTests = testGroup "Parser Tests"
+parser :: TestTree
+parser = testGroup "Parser Tests"
   [ testCase "Error when assigning a value to T" $ do
       let tokens = lexTricu "t = x" 
       case parseSingleExpr tokens of
         Left  _ -> return ()
         Right _ -> assertFailure "Expected failure when trying to assign the value of T"
+
   , testCase "Parse function definitions" $ do
       let input = "x = (\\a b c : a)"
           expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
       parseSingle input @?= expect
+
   , testCase "Parse nested Tree Calculus terms" $ do
       let input = "t (t t) t"
           expect = SApp (SApp TLeaf (SApp TLeaf TLeaf)) TLeaf
       parseSingle input @?= expect
+
   , testCase "Parse sequential Tree Calculus terms" $ do
       let input = "t t t"
           expect = SApp (SApp TLeaf TLeaf) TLeaf
       parseSingle input @?= expect
+
   , testCase "Parse mixed list literals" $ do
       let input = "[t (\"hello\") t]"
           expect = SList [TLeaf, SStr "hello", TLeaf]
       parseSingle input @?= expect
+
   , testCase "Parse function with applications" $ do
       let input  = "f = (\\x : t x)"
           expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
       parseSingle input @?= expect
+
   , testCase "Parse nested lists" $ do
       let input  = "[t [(t t)]]"
           expect = SList [TLeaf,SList [SApp TLeaf TLeaf]]
       parseSingle input @?= expect
+
   , testCase "Parse complex parentheses" $ do
       let input  = "t (t t (t t))"
           expect = SApp TLeaf (SApp (SApp TLeaf TLeaf) (SApp TLeaf TLeaf))
       parseSingle input @?= expect
+
   , testCase "Parse empty list" $ do
       let input  = "[]"
           expect = SList []
       parseSingle input @?= expect
+
   , testCase "Parse multiple nested lists" $ do
       let input  = "[[t t] [t (t t)]]"
           expect = SList [SList [TLeaf,TLeaf],SList [TLeaf,SApp TLeaf TLeaf]]
       parseSingle input @?= expect
+
   , testCase "Parse whitespace variance" $ do
       let input1 = "[t t]"
       let input2 = "[ t t ]"
           expect = SList [TLeaf, TLeaf]
       parseSingle input1 @?= expect
       parseSingle input2 @?= expect
+
   , testCase "Parse string in list" $ do
       let input  = "[(\"hello\")]"
           expect = SList [SStr "hello"]
       parseSingle input @?= expect
+
   , testCase "Parse parentheses inside list" $ do
       let input  = "[t (t t)]"
           expect = SList [TLeaf,SApp TLeaf TLeaf]
       parseSingle input @?= expect
+
   , testCase "Parse nested parentheses in function body" $ do
       let input  = "f = (\\x : t (t (t t)))"
           expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
       parseSingle input @?= expect
+
   , testCase "Parse lambda abstractions" $ do
       let input  = "(\\a : a)"
           expect = (SLambda ["a"] (SVar "a"))
       parseSingle input @?= expect
+
   , testCase "Parse multiple arguments to lambda abstractions" $ do
       let input  = "x = (\\a b : a)"
           expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
       parseSingle input @?= expect
+
   , testCase "Grouping T terms with parentheses in function application" $ do
       let input  = "x = (\\a : a)\nx (t)"
           expect = [SFunc "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
       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
   ]
 
-evaluationTests :: TestTree
-evaluationTests = testGroup "Evaluation Tests"
+simpleEvaluation :: TestTree
+simpleEvaluation = testGroup "Evaluation Tests"
   [ testCase "Evaluate single Leaf" $ do
       let input = "t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Leaf
+
   , testCase "Evaluate single Stem" $ do
       let input = "t t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Stem Leaf
+
   , testCase "Evaluate single Fork" $ do
       let input = "t t t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Fork Leaf Leaf
+
   , testCase "Evaluate nested Fork and Stem" $ do
       let input = "t (t t) t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?= Fork (Stem Leaf) Leaf
+
   , testCase "Evaluate `not` function" $ do
       let input = "t (t (t t) (t t t)) t"
       let ast = parseSingle input
       (result $ evalSingle Map.empty ast) @?=
         Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
+
   , testCase "Environment updates with definitions" $ do
       let input = "x = t\ny = x"
           env = 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 \
@@ -207,10 +243,17 @@ evaluationTests = testGroup "Evaluation Tests"
                   \ variablewithamuchlongername"
           env = evalTricu Map.empty (parseTricu input)
       (result env) @?= (Stem (Stem Leaf))
-  , testCase "Evaluate variable shadowing" $ do
+
+
+  , testCase "Immutable definitions" $ do
       let input = "x = t t\nx = t\nx"
           env = evalTricu Map.empty (parseTricu input)
-      (result env) @?= Leaf
+      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
@@ -218,194 +261,259 @@ evaluationTests = testGroup "Evaluation Tests"
       result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
   ]
 
-lambdaEvalTests :: TestTree
-lambdaEvalTests = testGroup "Lambda Evaluation Tests"
+lambdas :: TestTree
+lambdas = testGroup "Lambda Evaluation Tests"
   [ testCase "Lambda Identity Function" $ do
       let input = "id = (\\x : x)\nid t"
       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)"
   ]
 
-libraryTests :: TestTree
-libraryTests = testGroup "Library Tests"
+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"
+      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"
+      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"
+      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)"
+      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)"
+      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)"
+      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)"
+      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 []"
+      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)])"
+      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)"
+      let input = "equal? (t t t) (t t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
   ]
 
-fileEvaluationTests :: TestTree
-fileEvaluationTests = testGroup "Evaluation tests"
+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) @?= "2071"
+  , 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 \""
+  ]

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.6.0
+version:        0.7.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
@@ -18,6 +18,7 @@ executable tricu
       src
   default-extensions:
       DeriveDataTypeable
+      LambdaCase
       MultiWayIf
       OverloadedStrings
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -optl-pthread -fPIC
@@ -44,6 +45,7 @@ test-suite tricu-tests
   hs-source-dirs:      test, src
   default-extensions:
       DeriveDataTypeable
+      LambdaCase
       MultiWayIf
       OverloadedStrings
   build-depends: