Clean up and list SKI conversion fix

Also removes some broken list library functions

.gitignore

@@ -9,3 +9,4 @@
 WD
 bin/
 dist*
+.tricu_history

README.md

@@ -11,12 +11,11 @@ tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)
 ## Features
 
 - Tree Calculus operator: `t`
-- Assignments: `x = t t`
-- Immutable definitions
-- Lambda abstraction syntax: `id = (\a : a)`
+- Immutable definitions: `x = t t`
+- Lambda abstraction: `id = (a : a)`
 - List, Number, and String literals: `[(2) ("Hello")]` 
 - Function application: `not (not false)`
-- Higher order/first-class functions: `map (\a : append a "!") [("Hello")]`
+- Higher order/first-class functions: `map (a : append a "!") [("Hello")]`
 - Intensionality blurs the distinction between functions and data (see REPL examples)
 - Simple module system for code organization
 
@@ -24,15 +23,15 @@ tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)
 
 ```
 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 : append i " world!") [("Hello, ")])
+tricu < id = (a : a) -- Lambda abstraction is eliminated to tree calculus terms
+tricu < head (map (i : append i " world!") [("Hello, ")])
 tricu > "Hello,  world!"
-tricu < id (head (map (\i : append i " world!") [("Hello, ")]))
+tricu < id (head (map (i : append 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 < 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)
@@ -41,13 +40,21 @@ 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
+
+tricu < -- REPL Commands:
+tricu < !definitions  -- Lists all available definitions
+tricu < !output       -- Change output format (Tree, FSL, AST, etc.)
+tricu < !import       -- Import definitions from a file
+tricu < !exit         -- Exit the REPL
+tricu < !clear        -- ANSI screen clear
+tricu < !save         -- Save all REPL definitions to a file that you can !import
+tricu < !reset        -- Clear all REPL definitions
+tricu < !version      -- Print tricu version
 ```
 
 ## Installation and Use
 
-[Releases are available for Linux.](https://git.eversole.co/James/tricu/releases)
-
-Or you can easily build and run this project using [Nix](https://nixos.org/download/).
+You can easily build and run this project using [Nix](https://nixos.org/download/).
 
 - Quick Start (REPL): 
   - `nix run git+https://git.eversole.co/James/tricu`
@@ -84,6 +91,12 @@ tricu decode [OPTIONS]
                     Defaults to stdin.
 ```
 
+## Collaborating
+
+I am happy to accept issue reports, pull requests, or questions about tricu [via email](mailto:james@eversole.co).
+
+If you want to collaborate but don't want to email back-and-forth, please reach out via email once to let me know and I will provision a git.eversole.co account for you.
+
 ## Acknowledgements 
 
 Tree Calculus was discovered by [Barry Jay](https://github.com/barry-jay-personal/blog). 

demos/equality.tri

@@ -11,20 +11,17 @@ demo_true  = t t
 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)
-)
+demo_triage = a b c : t (t a b) c
+demo_matchBool = a b : demo_triage b (_ : a) (_ _ : a)
+
 -- 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
+-- As 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.
+-- representation possible. Between different languages that evaluate to tree
+-- calculus terms, the exact implementation of Lambda elimination may differ
+-- and lead to different trees even if they share extensional behavior.
 
 -- Let's see if these are the same:
 lambdaEqualsTC = equal? not_TC? not_Lambda?

demos/levelOrderTraversal.tri

@@ -18,15 +18,15 @@ main = exampleTwo
 --    /   /  \
 --   4   5    6
 
-label = \node : head node
+label = node : head node
 
-left = (\node : if (emptyList? node)
+left = node : (if (emptyList? node)
   []
   (if (emptyList? (tail node))
     []
     (head (tail node))))
 
-right = (\node : if (emptyList? node) 
+right = node : (if (emptyList? node)
   []
   (if (emptyList? (tail node))
     []
@@ -34,25 +34,25 @@ right = (\node : if (emptyList? node)
       []
       (head (tail (tail node))))))
 
-processLevel = y (\self queue : if (emptyList? queue) 
+processLevel = y (self queue : if (emptyList? queue)
   []
   (pair (map label queue) (self (filter
-    (\node : not? (emptyList? node)) 
+    (node : not? (emptyList? node))
       (append (map left queue) (map right queue))))))
 
-levelOrderTraversal_ = \a : processLevel (t a t)
+levelOrderTraversal_ = a : processLevel (t a t)
 
-toLineString = y (\self levels : if (emptyList? levels) 
+toLineString = y (self levels : if (emptyList? levels)
   ""
   (append
-    (append (map (\x : append x " ") (head levels)) "") 
+    (append (map (x : append x " ") (head levels)) "")
     (if (emptyList? (tail levels)) "" (append (t (t 10 t) t) (self (tail levels))))))
 
-levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
+levelOrderToString = s : toLineString (levelOrderTraversal_ s)
 
-flatten = foldl (\acc x : append acc x) ""
+flatten = foldl (acc x : append acc x) ""
 
-levelOrderTraversal = \s : append (t 10 t) (flatten (levelOrderToString s))
+levelOrderTraversal = s : append (t 10 t) (flatten (levelOrderToString s))
 
 exampleOne = levelOrderTraversal [("1")
                                  [("2") [("4") t t] t]

demos/patternMatching.tri

@@ -0,0 +1,37 @@
+!import "../lib/patterns.tri" !Local
+
+-- We can do conditional pattern matching by providing a list of lists, where
+-- each sublist contains a boolean expression and a function to return if said
+-- boolean expression evaluates to true.
+
+value = 42
+main  = match value [[(equal? "Hello") (_ : ", world!")] [(equal? 42) (_ : "The answer.")]]
+
+-- < main
+-- > "The answer."
+
+matchExample = (x : match x
+  [[(equal? 1)  (_ : "one")]
+   [(equal? 2)  (_ : "two")]
+   [(equal? 3)  (_ : "three")]
+   [(equal? 4)  (_ : "four")]
+   [(equal? 5)  (_ : "five")]
+   [(equal? 6)  (_ : "six")]
+   [(equal? 7)  (_ : "seven")]
+   [(equal? 8)  (_ : "eight")]
+   [(equal? 9)  (_ : "nine")]
+   [(equal? 10) (_ : "ten")]
+   [ otherwise  (_ : "I ran out of fingers!")]])
+
+-- < matchExample 3
+-- > "three"
+-- < matchExample 5
+-- > "five"
+-- < matchExample 9
+-- > "nine"
+-- < matchExample 11
+-- > "I ran out of fingers!"
+-- < matchExample "three"
+-- > "I ran out of fingers!"
+-- < matchExample [("hello") ("world")]
+-- > "I ran out of fingers!"

demos/size.tri

@@ -3,11 +3,9 @@
 
 main = size size
 
-size = (\x :
-  (y (\self x :
-    compose succ
-      (triage
-        (\x : x)
+size = x : y (self x : compose succ (triage
+  id
   self
-        (\x y : compose (self x) (self y))
-        x)) x 0))
+  (x y : compose (self x) (self y))
+  x)
+) x 0

demos/toSource.tri

@@ -18,25 +18,25 @@ main = toSource not?
 sourceLeaf = t (head "t")
 
 -- Stem case
-sourceStem = (\convert : (\a rest :
+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.
+          (t (head ")") rest)))))   -- Close with ")" and append the rest.
 
 -- Fork case
-sourceFork = (\convert : (\a b rest :
+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.
+              (t (head ")") rest))))))) -- Close with ")" and append the rest.
 
 -- Wrapper around triage 
-toSource_ = y (\self arg :
+toSource_ = y (self arg :
   triage
     sourceLeaf        -- `triage` "a" case, Leaf
     (sourceStem self) -- `triage` "b" case, Stem
@@ -44,7 +44,7 @@ toSource_ = y (\self arg :
     arg)              -- The term to be inspected
 
 -- toSource takes a single TC term and returns a String
-toSource = \v : toSource_ v ""
+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

@@ -34,6 +34,7 @@
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
             haskellPackages.cabal-install
+            haskellPackages.ghc-events
             haskellPackages.ghcid
             customGHC
             upx

lib/base.tri

@@ -1,74 +1,74 @@
 false = t
 _     = t
 true  = t t
-id    = \a : a
-const = \a b : a
+id    = a : a
+const = a b : a
 pair  = t
-if    = \cond then else : t (t else (t t then)) t cond
+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))
+y = ((mut wait fun : wait mut (x : fun (wait mut x)))
+     (x : x x)
+     (a0 a1 a2 : t (t a0) (t t a2) a1))
 
-compose = \f g x : f (g x)
+compose = f g x : f (g x)
 
-triage = \leaf stem fork : t (t leaf stem) fork
-test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
+triage = leaf stem fork : t (t leaf stem) fork
+test   = triage "Leaf" (_ : "Stem") (_ _ : "Fork")
 
-matchBool = (\ot of : triage
+matchBool = (ot of : triage
   of
-  (\_ : ot)
-  (\_ _ : ot)
+  (_ : ot)
+  (_ _ : ot)
 )
 
 lAnd = (triage
-  (\_     : false)
-  (\_ x   : x)
-  (\_ _ x : x))
+  (_     : false)
+  (_ x   : x)
+  (_ _ x : x))
 
 lOr = (triage
-  (\x     : x)
-  (\_ _   : true)
-  (\_ _ _ : true))
+  (x     : x)
+  (_ _   : true)
+  (_ _ _ : true))
 
-matchPair = \a   : triage _ _ a
+matchPair = a : triage _ _ a
 
 not? = matchBool false true
-and? = matchBool id (\_ : false)
+and? = matchBool id (_ : false)
 
-or? = (\x z : 
+or? = (x z : 
   matchBool 
     (matchBool true true z)
     (matchBool true false z)
     x)
 
-xor? = (\x z : 
+xor? = (x z : 
   matchBool 
     (matchBool false true z)
     (matchBool true false z)
     x)
 
-equal? = y (\self : triage
+equal? = y (self : triage
   (triage
     true
-    (\_   : false)
-    (\_ _ : false))
-  (\ax :
+    (_   : false)
+    (_ _ : false))
+  (ax :
     triage
       false
       (self ax)
-      (\_ _ : false))
-  (\ax ay :
+      (_ _ : false))
+  (ax ay :
     triage
       false
-      (\_ : false)
-      (\bx by : lAnd (self ax bx) (self ay by))))
+      (_ : false)
+      (bx by : lAnd (self ax bx) (self ay by))))
 
-succ = y (\self :
+succ = y (self :
   triage
     1
     t
     (triage
       (t (t t))
-      (\_ tail : t t (self tail))
+      (_ tail : t t (self tail))
       t))

lib/list.tri

@@ -1,77 +1,70 @@
 !import "base.tri" !Local
 
-matchList = \a b : triage a _ b
+_ = t
 
-emptyList? = matchList true (\_ _ : false)
-head = matchList t (\head _ : head)
-tail = matchList t (\_ tail : tail)
+matchList = a b : triage a _ b
 
-append = y (\self : matchList
-  (\k : k)
-  (\h r k : pair h (self r k)))
+emptyList? = matchList true (_ _ : false)
+head = matchList t (head _ : head)
+tail = matchList t (_ tail : tail)
 
-lExist? = y (\self x : matchList
+append = y (self : matchList
+  (k : k)
+  (h r k : pair h (self r k)))
+
+lExist? = y (self x : matchList
   false
-  (\h z : or? (equal? x h) (self x z)))
+  (h z : or? (equal? x h) (self x z)))
 
-map_ = y (\self :
+map_ = y (self :
   matchList
-    (\_ : t)
-    (\head tail f : pair (f head) (self tail f)))
-map = \f l : map_ l f
+    (_ : t)
+    (head tail f : pair (f head) (self tail f)))
+map = f l : map_ l f
 
-filter_ = y (\self : matchList
-  (\_ : t)
-  (\head tail f : matchBool (t head) id (f head) (self tail f)))
-filter  = \f l : filter_ l f
+filter_ = y (self : matchList
+  (_ : t)
+  (head tail f : matchBool (t head) id (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
+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
+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
 
-length = y (\self : matchList
+length = y (self : matchList
   0
-  (\_ tail : succ (self tail)))
+  (_ tail : succ (self tail)))
 
-reverse = y (\self : matchList
+reverse = y (self : matchList
   t
-  (\head tail : append (self tail) (pair head t)))
+  (head tail : append (self tail) (pair head t)))
 
-snoc = y (\self x : matchList
+snoc = y (self x : matchList
   (pair x t)
-  (\h z : pair h (self x z)))
+  (h z : pair h (self x z)))
 
-count = y (\self x : matchList
+count = y (self x : matchList
   0
-  (\h z : matchBool
+  (h z : matchBool
     (succ (self x z))
     (self x z)
     (equal? x h)))
 
-last = y (\self : matchList
+last = y (self : matchList
   t
-  (\hd tl : matchBool
+  (hd tl : matchBool
     hd
     (self tl)
     (emptyList? tl)))
 
-all? = y (\self pred : matchList
+all? = y (self pred : matchList
   true
-  (\h z : and? (pred h) (self pred z)))
+  (h z : and? (pred h) (self pred z)))
 
-any? = y (\self pred : matchList
+any? = y (self pred : matchList
   false
-  (\h z : or? (pred h) (self pred z)))
+  (h z : or? (pred h) (self pred z)))
 
-unique_ = y (\self seen : matchList
-  t
-  (\head rest : matchBool
-    (self seen rest)
-    (pair head (self (pair head seen) rest))
-    (lExist? head seen)))
-unique = \xs : unique_ t xs
-
-intersect = \xs ys : filter (\x : lExist? x ys) xs
-union     = \xs ys : unique (append xs ys)
+intersect = xs ys : filter (x : lExist? x ys) xs

lib/patterns.tri

@@ -0,0 +1,24 @@
+!import "base.tri" !Local
+!import "list.tri" List
+
+match_ = y (self value patterns :
+  triage
+    t
+    (_ : t)
+    (pattern rest :
+      triage
+        t
+        (_ : t)
+        (test result :
+          if (test value)
+             (result value)
+             (self value rest))
+        pattern)
+    patterns)
+
+match = (value patterns :
+  match_ value (List.map (sublist :
+    pair (List.head sublist) (List.head (List.tail sublist)))
+    patterns))
+
+otherwise = const (t t)

src/Eval.hs

@@ -62,24 +62,39 @@ evalAST env term
 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 == SApp (SVar f) (SApp (SVar g) (SVar x)) = _B
-    -- General elimination
-    go (SLambda (v:vs) body)
+    go term
+      | etaReduction term   = elimLambda $ etaReduceResult term
+      | triagePattern term  = _TRI
+      | composePattern term = _B
+      | lambdaList term     = elimLambda $ lambdaListResult term
+      | nestedLambda term   = nestedLambdaResult term
+      | application term    = applicationResult term
+      | otherwise           = term
+
+    etaReduction (SLambda [v] (SApp f (SVar x))) = v == x && not (isFree v f)
+    etaReduction _ = False
+    etaReduceResult (SLambda [_] (SApp f _)) = f
+
+    triagePattern (SLambda [a] (SLambda [b] (SLambda [c] body))) = body == triageBody a b c
+    triagePattern _ = False
+
+    composePattern (SLambda [f] (SLambda [g] (SLambda [x] body))) = body == composeBody f g x
+    composePattern _ = False
+
+    lambdaList (SLambda [_] (SList _)) = True
+    lambdaList _ = False
+    lambdaListResult (SLambda [v] (SList xs)) = SLambda [v] (foldr wrapTLeaf TLeaf xs)
+    wrapTLeaf m r = SApp (SApp TLeaf m) r
+
+    nestedLambda (SLambda (_:_) _) = True
+    nestedLambda _ = False
+    nestedLambdaResult (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
+
+    application (SApp _ _) = True
+    application _ = False
+    applicationResult (SApp f g) = SApp (elimLambda f) (elimLambda g)
 
     toSKI x (SVar y)
       | x == y           = _I
@@ -87,30 +102,38 @@ elimLambda = go
     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 (SList xs)
+      | not (isFree x (SList xs)) = SApp _K (SList xs)
+      | otherwise = SList (map (toSKI x) xs)
     toSKI x t
       | not (isFree x t) = SApp _K t
       | otherwise        = errorWithoutStackTrace "Unhandled toSKI conversion"
 
+    -- Combinators and special forms
     _S   = parseSingle "t (t (t t t)) t"
     _K   = parseSingle "t t"
     _I   = parseSingle "t (t (t t)) t"
     _B   = parseSingle "t (t (t t (t (t (t t t)) t))) (t t)"
-    _TRIAGE  = parseSingle "t (t (t t (t (t (t t t))))) t"
+    _TRI = parseSingle "t (t (t t (t (t (t t t))))) t"
+    
+    -- Pattern bodies
+    triageBody a b c = SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c)
+    composeBody f g x = SApp (SVar f) (SApp (SVar g) (SVar x))
 
 isFree :: String -> TricuAST -> Bool
 isFree x = Set.member x . freeVars
 
 freeVars :: TricuAST -> Set.Set String
 freeVars (SVar    v    ) = Set.singleton v
-freeVars (SInt    _    ) = Set.empty
-freeVars (SStr    _    ) = Set.empty
 freeVars (SList   s    ) = foldMap freeVars s
+freeVars (SLambda v b  ) = foldr Set.delete (freeVars b) v
 freeVars (SApp    f a  ) = freeVars f <> freeVars a
-freeVars  TLeaf          = Set.empty
+freeVars (TFork   l r  ) = freeVars l <> freeVars r
 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
+freeVars (SInt    _    ) = Set.empty
+freeVars (SStr    _    ) = Set.empty
+freeVars  TLeaf          = Set.empty
 freeVars  _              = Set.empty
 
 reorderDefs :: Env -> [TricuAST] -> [TricuAST]
@@ -128,7 +151,7 @@ reorderDefs env defs
     graph = buildDepGraph defsOnly
     sortedDefs = sortDeps graph
     defMap = Map.fromList [(name, def) | def@(SDef name _ _) <- defsOnly]
-    orderedDefs = map (\name -> defMap Map.! name) sortedDefs
+    orderedDefs = map (defMap Map.!) sortedDefs
 
     freeVarsDefs = foldMap snd defsWithFreeVars
     freeVarsOthers = foldMap freeVars others
@@ -136,7 +159,7 @@ reorderDefs env defs
     validNames = Set.fromList defNames `Set.union` Set.fromList (Map.keys env)
     missingDeps = Set.toList (allFreeVars `Set.difference` validNames)
 
-    isDef (SDef _ _ _) = True
+    isDef SDef {} = True
     isDef _       = False
 
 buildDepGraph :: [TricuAST] -> Map.Map String (Set.Set String)

src/FileEval.hs

@@ -6,6 +6,7 @@ import Parser
 import Research
 
 import Data.List       (partition)
+import Data.Maybe      (mapMaybe)
 import Control.Monad   (foldM)
 import System.IO
 import System.FilePath (takeDirectory, normalise, (</>))
@@ -13,6 +14,26 @@ import System.FilePath (takeDirectory, normalise, (</>))
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 
+extractMain :: Env -> Either String T
+extractMain env =
+  case Map.lookup "main" env of
+    Just result -> Right result
+    Nothing -> Left "No `main` function detected"
+
+processImports :: Set.Set FilePath -> FilePath -> FilePath -> [TricuAST]
+                 -> Either String ([TricuAST], [(FilePath, String, FilePath)])
+processImports seen base currentPath asts =
+  let (imports, nonImports) = partition isImp asts
+      importPaths = mapMaybe getImportInfo imports
+  in if currentPath `Set.member` seen
+     then Left $ "Encountered cyclic import: " ++ currentPath
+     else Right (nonImports, importPaths)
+  where
+    isImp (SImport _ _) = True
+    isImp _ = False
+    getImportInfo (SImport p n) = Just (p, n, makeRelativeTo currentPath p)
+    getImportInfo _ = Nothing
+
 evaluateFileResult :: FilePath -> IO T
 evaluateFileResult filePath = do
   contents <- readFile filePath
@@ -20,11 +41,11 @@ evaluateFileResult filePath = do
   case parseProgram tokens of
     Left err -> errorWithoutStackTrace (handleParseError err)
     Right ast -> do
-      ast <- preprocessFile filePath
-      let finalEnv = evalTricu Map.empty ast
-      case Map.lookup "main" finalEnv of
-        Just finalResult -> return finalResult
-        Nothing -> errorWithoutStackTrace "No `main` function detected"
+      processedAst <- preprocessFile filePath
+      let finalEnv = evalTricu Map.empty processedAst
+      case extractMain finalEnv of
+        Right result -> return result
+        Left err -> errorWithoutStackTrace err
 
 evaluateFile :: FilePath -> IO Env
 evaluateFile filePath = do
@@ -50,38 +71,26 @@ preprocessFile :: FilePath -> IO [TricuAST]
 preprocessFile p = preprocessFile' Set.empty p p
 
 preprocessFile' :: Set.Set FilePath -> FilePath -> FilePath -> IO [TricuAST]
-preprocessFile' s b p
-  | p `Set.member` s =
-      errorWithoutStackTrace $ "Encountered cyclic import: " ++ p
-  | otherwise = do
-      c <- readFile p
-      let t = lexTricu c
-      case parseProgram t of
-        Left e -> errorWithoutStackTrace (handleParseError e)
-        Right a -> do
-          let (i, n) = partition isImp a
-          let s' = Set.insert p s
-          r <- concat <$>
-            mapM (procImp s' "" p) i
-          pure $ r ++ n
+preprocessFile' seen base currentPath = do
+  contents <- readFile currentPath
+  let tokens = lexTricu contents
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right ast ->
+      case processImports seen base currentPath ast of
+        Left err -> errorWithoutStackTrace err
+        Right (nonImports, importPaths) -> do
+          let seen' = Set.insert currentPath seen
+          imported <- concat <$> mapM (processImportPath seen' base) importPaths
+          pure $ imported ++ nonImports
   where
-    isImp :: TricuAST -> Bool
+    processImportPath seen base (path, name, importPath) = do
+      ast <- preprocessFile' seen base importPath
+      pure $ map (nsDefinition (if name == "!Local" then "" else name))
+           $ filter (not . isImp) ast
     isImp (SImport _ _) = True
     isImp _ = False
 
-    procImp :: Set.Set FilePath -> String -> FilePath -> TricuAST -> IO [TricuAST]
-    procImp s m f (SImport p "!Local") = do
-      let ip = makeRelativeTo f p
-      a <- preprocessFile' s b ip
-      let d = filter (not . isImp) a
-      pure $ map (nsDefinition m) d
-    procImp s _ f (SImport p n) = do
-      let ip = makeRelativeTo f p
-      a <- preprocessFile' s b ip
-      let d = filter (not . isImp) a
-      pure $ map (nsDefinition n) d
-    procImp _ _ _ _ = error "Unexpected non-import in processImport"
-
 makeRelativeTo :: FilePath -> FilePath -> FilePath
 makeRelativeTo f i =
     let d = takeDirectory f

src/Lexer.hs

@@ -3,6 +3,7 @@ module Lexer where
 import Research
 
 import Control.Monad               (void)
+import Data.Functor                (($>))
 import Data.Void
 import Text.Megaparsec
 import Text.Megaparsec.Char hiding (space)
@@ -40,7 +41,6 @@ tricuLexer = do
       , try stringLiteral
       , assign
       , colon
-      , backslash
       , openParen
       , closeParen
       , openBracket
@@ -54,7 +54,7 @@ lexTricu input = case runParser tricuLexer "" input of
 
 
 keywordT :: Lexer LToken
-keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
+keywordT = string "t" *> notFollowedBy alphaNumChar $> LKeywordT
 
 identifier :: Lexer LToken
 identifier = do
@@ -63,7 +63,7 @@ identifier = do
               <|> digitChar <|> char '_' <|> char '-' <|> char '?'
               <|> char '$'  <|> char '#' <|> char '@' <|> char '%'
   let name = first : rest
-  if (name == "t" || name == "!result")
+  if name == "t" || name == "!result"
     then fail "Keywords (`t`, `!result`) cannot be used as an identifier"
     else return (LIdentifier name)
 
@@ -76,7 +76,7 @@ namespace = do
   return (LNamespace name)
 
 dot :: Lexer LToken
-dot = char '.' *> pure LDot
+dot = char '.' $> LDot
 
 lImport :: Lexer LToken
 lImport = do
@@ -88,28 +88,25 @@ lImport = do
   return (LImport path name)
 
 assign :: Lexer LToken
-assign = char '=' *> pure LAssign
+assign = char '=' $> LAssign
 
 colon :: Lexer LToken
-colon = char ':' *> pure LColon
-
-backslash :: Lexer LToken
-backslash = char '\\' *> pure LBackslash
+colon = char ':' $> LColon
 
 openParen :: Lexer LToken
-openParen = char '(' *> pure LOpenParen
+openParen = char '(' $> LOpenParen
 
 closeParen :: Lexer LToken
-closeParen = char ')' *> pure LCloseParen
+closeParen = char ')' $> LCloseParen
 
 openBracket :: Lexer LToken
-openBracket = char '[' *> pure LOpenBracket
+openBracket = char '[' $> LOpenBracket
 
 closeBracket :: Lexer LToken
-closeBracket = char ']' *> pure LCloseBracket
+closeBracket = char ']' $> LCloseBracket
 
 lnewline :: Lexer LToken
-lnewline = char '\n' *> pure LNewline
+lnewline = char '\n' $> LNewline
 
 sc :: Lexer ()
 sc = space
@@ -125,7 +122,22 @@ integerLiteral = do
 stringLiteral :: Lexer LToken
 stringLiteral = do
   char '"'
-  content <- many (noneOf ['"'])
-  char '"' --"
+  content <- manyTill Lexer.charLiteral (char '"')
   return (LStringLiteral content)
 
+charLiteral :: Lexer Char
+charLiteral = escapedChar <|> normalChar
+  where
+    normalChar = noneOf ['"', '\\']
+    escapedChar = do
+      void $ char '\\'
+      c <- oneOf ['n', 't', 'r', 'f', 'b', '\\', '"', '\'']
+      return $ case c of
+        'n'  -> '\n'
+        't'  -> '\t'
+        'r'  -> '\r'
+        'f'  -> '\f'
+        'b'  -> '\b'
+        '\\' -> '\\'
+        '"'  -> '"'
+        '\'' -> '\''

src/Main.hs

@@ -63,18 +63,17 @@ main = do
   case args of
     Repl -> do
       putStrLn "Welcome to the tricu REPL"
-      putStrLn "You can exit with `CTRL+D` or the `!exit` command.`"
+      putStrLn "You may exit with `CTRL+D` or the `!exit` command."
+      putStrLn "Try typing `!` with tab completion for more commands."
       repl Map.empty
     Evaluate { file = filePaths, form = form } -> do
       result <- case filePaths of
-        [] -> do
-          t <- getContents
-          pure $ runTricu t
+        [] -> runTricuT <$> getContents
         (filePath:restFilePaths) -> do
             initialEnv <- evaluateFile filePath
             finalEnv <- foldM evaluateFileWithContext initialEnv restFilePaths
             pure $ mainResult finalEnv
-      let fRes = formatResult form result
+      let fRes = formatT form result
       putStr fRes
     TDecode { file = filePaths } -> do
       value <- case filePaths of
@@ -82,8 +81,48 @@ main = do
         (filePath:_) -> readFile filePath
       putStrLn $ decodeResult $ result $ evalTricu Map.empty $ parseTricu value
 
-runTricu :: String -> T
-runTricu input =
+-- Simple interfaces
+
+runTricu :: String -> String
+runTricu = formatT TreeCalculus . runTricuT
+
+runTricuT :: String -> T
+runTricuT input =
   let asts     = parseTricu input
       finalEnv = evalTricu Map.empty asts
    in result finalEnv
+
+runTricuEnv :: Env -> String -> String
+runTricuEnv env = formatT TreeCalculus . runTricuTEnv env
+
+runTricuTEnv :: Env -> String -> T
+runTricuTEnv env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+   in result finalEnv
+
+runTricuWithEnvT :: String -> (Env, T)
+runTricuWithEnvT input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+   in (finalEnv, result finalEnv)
+
+runTricuWithEnv :: String -> (Env, String)
+runTricuWithEnv input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+      res      = result finalEnv
+   in (finalEnv, formatT TreeCalculus res)
+
+runTricuEnvWithEnvT :: Env -> String -> (Env, T)
+runTricuEnvWithEnvT env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+   in (finalEnv, result finalEnv)
+
+runTricuEnvWithEnv :: Env -> String -> (Env, String)
+runTricuEnvWithEnv env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+      res      = result finalEnv
+   in (finalEnv, formatT TreeCalculus res)

src/Parser.hs

@@ -130,7 +130,6 @@ parseFunctionM = do
 parseLambdaM :: ParserM TricuAST
 parseLambdaM = do
   let ident = (\case LIdentifier _ -> True; _ -> False)
-  _      <- satisfyM (== LBackslash)
   params <- some (satisfyM ident)
   _      <- satisfyM (== LColon)
   scnParserM
@@ -145,11 +144,11 @@ parseLambdaExpressionM = choice
 
 parseAtomicLambdaM :: ParserM TricuAST
 parseAtomicLambdaM = choice
-  [ parseVarM
+  [ try parseLambdaM
+  , parseVarM
   , parseTreeLeafM
   , parseLiteralM
   , parseListLiteralM
-  , try parseLambdaM
   , between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseLambdaExpressionM
   ]
 
@@ -205,7 +204,8 @@ parseTreeLeafOrParenthesizedM = choice
 
 parseAtomicM :: ParserM TricuAST
 parseAtomicM = choice
-  [ parseVarM
+  [ try parseLambdaM
+  , parseVarM
   , parseTreeLeafM
   , parseListLiteralM
   , parseGroupedM

src/REPL.hs

@@ -6,68 +6,153 @@ import Lexer
 import Parser
 import Research
 
-import Control.Exception      (SomeException, catch)
-import Control.Monad.IO.Class (liftIO)
+import Control.Exception         (IOException, SomeException, catch
+                                 , displayException)
+import Control.Monad             (forM_)
 import Control.Monad.Catch       (handle, MonadCatch)
-import Data.Char              (isSpace)
-import Data.List              ( dropWhile
-                              , dropWhileEnd
-                              , intercalate
-                              , isPrefixOf)
+import Control.Monad.IO.Class    (liftIO)
+import Control.Monad.Trans.Class (lift)
+import Control.Monad.Trans.Maybe (MaybeT(..), runMaybeT)
+import Data.Char                 (isSpace, isUpper)
+import Data.List                 (dropWhile, dropWhileEnd, isPrefixOf)
+import Data.Version (showVersion)
+import Paths_tricu (version)
 import System.Console.Haskeline
 
 import qualified Data.Map as Map
+import qualified Data.Text as T
+import qualified Data.Text.IO as T
 
 repl :: Env -> IO ()
-repl env = runInputT defaultSettings (withInterrupt (loop env True))
+repl env = runInputT settings (withInterrupt (loop env Decode))
   where
-    loop :: Env -> Bool -> InputT IO ()
-    loop env decode = handle (interruptHandler env decode) $ do
+    settings :: Settings IO
+    settings = Settings
+      { complete = completeWord Nothing " \t" completeCommands
+      , historyFile = Just "~/.local/state/tricu/history"
+      , autoAddHistory = True
+      }
+
+    completeCommands :: String -> IO [Completion]
+    completeCommands str = return $ map simpleCompletion $
+      filter (str `isPrefixOf`) commands
+      where
+        commands = [ "!exit"
+                   , "!output"
+                   , "!definitions"
+                   , "!import"
+                   , "!clear"
+                   , "!save"
+                   , "!reset"
+                   , "!version"
+                   ]
+
+    loop :: Env -> EvaluatedForm -> InputT IO ()
+    loop env form = handle (interruptHandler env form) $ do
       minput <- getInputLine "tricu < "
       case minput of
         Nothing -> outputStrLn "Exiting tricu"
         Just s
-          | strip s == "" -> loop env decode
+          | strip s == "" -> loop env form
           | strip s == "!exit" -> outputStrLn "Exiting tricu"
-          | strip s == "!decode" -> do
-              outputStrLn $ "Decoding " ++ (if decode then "disabled" else "enabled")
-              loop env (not decode)
-          | "!import" `isPrefixOf` strip s -> do
-              let afterImport = dropWhile (== ' ') $ drop (length ("!import" :: String)) (strip s)
-              if not (null afterImport)
-                then outputStrLn "Warning: REPL imports are interactive; \
-                                  \additional arguments are ignored."
-                else pure ()
-              path <- getInputLine "File path to load < "
-              case path of
-                Nothing -> do
-                  outputStrLn "No input received; stopping import."
-                  loop env decode
-                Just p -> do
-                  loadedEnv <- liftIO $ evaluateFileWithContext env
-                    (strip p) `catch` \e -> errorHandler env e
-                  loop (Map.delete "!result" (Map.union loadedEnv env)) decode
-          | take 2 s == "--" -> loop env decode
+          | strip s == "!clear" -> do
+              liftIO $ putStr "\ESC[2J\ESC[H"
+              loop env form
+          | strip s == "!reset" -> do
+              outputStrLn "Environment reset to initial state"
+              loop Map.empty form
+          | strip s == "!version" -> do
+              outputStrLn $ "tricu version " ++ showVersion version
+              loop env form
+          | "!save" `isPrefixOf` strip s -> handleSave env form
+          | strip s == "!output" -> handleOutput env form
+          | strip s == "!definitions" -> do
+              let defs = Map.keys $ Map.delete "!result" env
+              if null defs
+                then outputStrLn "No definitions discovered."
+                else do
+                  outputStrLn "Available definitions:"
+                  mapM_ outputStrLn defs
+              loop env form
+          | "!import" `isPrefixOf` strip s -> handleImport env form
+          | take 2 s == "--" -> loop env form
           | otherwise -> do
-              newEnv <- liftIO $ processInput env s decode `catch` errorHandler env
-              loop newEnv decode
+              newEnv <- liftIO $ processInput env s form `catch` errorHandler env
+              loop newEnv form
 
-    interruptHandler :: Env -> Bool -> Interrupt -> InputT IO ()
-    interruptHandler env decode _ = do
+    handleOutput :: Env -> EvaluatedForm -> InputT IO ()
+    handleOutput env currentForm = do
+      let formats = [Decode, TreeCalculus, FSL, AST, Ternary, Ascii]
+      outputStrLn "Available output formats:"
+      mapM_ (\(i, f) -> outputStrLn $ show i ++ ". " ++ show f)
+        (zip [1..] formats)
+
+      result <- runMaybeT $ do
+        input <- MaybeT $ getInputLine "Select output format (1-6) < "
+        case reads input of
+          [(n, "")] | n >= 1 && n <= 6 ->
+            return $ formats !! (n-1)
+          _ -> MaybeT $ return Nothing
+
+      case result of
+        Nothing -> do
+          outputStrLn "Invalid selection. Keeping current output format."
+          loop env currentForm
+        Just newForm -> do
+          outputStrLn $ "Output format changed to: " ++ show newForm
+          loop env newForm
+
+    handleImport :: Env -> EvaluatedForm -> InputT IO ()
+    handleImport env form = do
+      res <- runMaybeT $ do
+        let fset = setComplete completeFilename defaultSettings
+        path <- MaybeT $ runInputT fset $
+          getInputLineWithInitial "File path to load < " ("", "")
+
+        text <- MaybeT $ liftIO $ handle (\e -> do
+            putStrLn $ "Error reading file: " ++ displayException (e :: IOException)
+            return Nothing
+          ) $ Just <$> readFile (strip path)
+
+        case parseProgram (lexTricu text) of
+          Left err -> do
+            lift $ outputStrLn $ "Parse error: " ++ handleParseError err
+            MaybeT $ return Nothing
+          Right ast -> do
+            ns <- MaybeT $ runInputT defaultSettings $
+              getInputLineWithInitial "Namespace (or !Local for no namespace) < " ("", "")
+
+            let name = strip ns
+            if (name /= "!Local" && (null name || not (isUpper (head name)))) then do
+                lift $ outputStrLn "Namespace must start with an uppercase letter"
+                MaybeT $ return Nothing
+            else do
+                prog <- liftIO $ preprocessFile (strip path)
+                let code = case name of
+                      "!Local" -> prog
+                      _ -> nsDefinitions name prog
+                    env' = evalTricu env code
+                return env'
+      case res of
+        Nothing -> do
+          outputStrLn "Import cancelled"
+          loop env form
+        Just env' ->
+          loop (Map.delete "!result" env') form
+
+    interruptHandler :: Env -> EvaluatedForm -> Interrupt -> InputT IO ()
+    interruptHandler env form _ = do
       outputStrLn "Interrupted with CTRL+C\n\
                   \You can use the !exit command or CTRL+D to exit"
-      loop env decode
+      loop env form
 
-    processInput :: Env -> String -> Bool -> IO Env
-    processInput env input decode = do
+    processInput :: Env -> String -> EvaluatedForm -> IO Env
+    processInput env input form = do
       let asts   = parseTricu input
           newEnv = evalTricu env asts
       case Map.lookup "!result" newEnv of
         Just r -> do
-          putStrLn $ "tricu > " ++ 
-            if decode 
-              then decodeResult r
-              else show r
+          putStrLn $ "tricu > " ++ formatT form r
         Nothing -> pure ()
       return newEnv
 
@@ -78,3 +163,28 @@ repl env = runInputT defaultSettings (withInterrupt (loop env True))
 
     strip :: String -> String
     strip = dropWhileEnd isSpace . dropWhile isSpace
+
+    handleSave :: Env -> EvaluatedForm -> InputT IO ()
+    handleSave env form = do
+      let fset = setComplete completeFilename defaultSettings
+      path <- runInputT fset $
+        getInputLineWithInitial "File to save < " ("", "")
+
+      case path of
+        Nothing -> do
+          outputStrLn "Save cancelled"
+          loop env form
+        Just p -> do
+          let definitions = Map.toList $ Map.delete "!result" env
+              filepath = strip p
+
+          outputStrLn "Starting save..."
+          liftIO $ writeFile filepath ""
+          outputStrLn "File created..."
+          forM_ definitions $ \(name, value) -> do
+            let content = name ++ " = " ++ formatT TreeCalculus value ++ "\n"
+            outputStrLn $ "Writing definition: " ++ name ++ " with length " ++ show (length content)
+            liftIO $ appendFile filepath content
+          outputStrLn $ "Saved " ++ show (length definitions) ++ " definitions to " ++ p
+
+          loop env form

src/Research.hs

@@ -1,6 +1,5 @@
 module Research where
 
-import Control.Monad.State
 import Data.List                 (intercalate)
 import Data.Map                  (Map)
 import Data.Text                 (Text, replace)
@@ -16,7 +15,7 @@ data T = Leaf | Stem T | Fork T T
 -- Abstract Syntax Tree for tricu
 data TricuAST
   = SVar String
-  | SInt Int
+  | SInt Integer
   | SStr String
   | SList [TricuAST]
   | SDef String [String] TricuAST
@@ -34,12 +33,11 @@ data LToken
   = LKeywordT
   | LIdentifier String
   | LNamespace String
-  | LIntegerLiteral Int
+  | LIntegerLiteral Integer
   | LStringLiteral String
   | LAssign
   | LColon
   | LDot
-  | LBackslash
   | LOpenParen
   | LCloseParen
   | LOpenBracket
@@ -55,15 +53,24 @@ data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii | Decode
 -- Environment containing previously evaluated TC terms
 type Env = Map.Map String T
 
--- Tree Calculus Reduction
+-- Tree Calculus Reduction Rules
+{- 
+  The t operator is left associative.
+  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
+-}
 apply :: T -> T -> T
+apply (Fork Leaf a)         _         = a
+apply (Fork (Stem a) b) c             = apply (apply a c) (apply b c)
+apply (Fork (Fork a  b) c)  Leaf      = a
+apply (Fork (Fork a  b) c) (Stem u)   = apply b u
+apply (Fork (Fork a  b) c) (Fork u v) = apply (apply c u) v
+-- Left associative `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
 
 -- Booleans
 _false :: T
@@ -77,9 +84,9 @@ _not = Fork (Fork _true (Fork Leaf _false)) Leaf
 
 -- Marshalling
 ofString :: String -> T
-ofString str = ofList (map ofNumber (map fromEnum str))
+ofString str = ofList $ map (ofNumber . toInteger . fromEnum) str
 
-ofNumber :: Int -> T
+ofNumber :: Integer -> T
 ofNumber 0 = Leaf
 ofNumber n =
   Fork
@@ -87,10 +94,9 @@ ofNumber n =
     (ofNumber (n `div` 2))
 
 ofList :: [T] -> T
-ofList [] = Leaf
-ofList (x:xs) = Fork x (ofList xs)
+ofList = foldr Fork Leaf
 
-toNumber :: T -> Either String Int
+toNumber :: T -> Either String Integer
 toNumber Leaf = Right 0
 toNumber (Fork Leaf rest) = case toNumber rest of
   Right n -> Right (2 * n)
@@ -102,7 +108,7 @@ toNumber _ = Left "Invalid Tree Calculus number"
 
 toString :: T -> Either String String
 toString tc = case toList tc of
-  Right list -> traverse (fmap toEnum . toNumber) list
+  Right list -> traverse (fmap (toEnum . fromInteger) . toNumber) list
   Left err -> Left "Invalid Tree Calculus string"
 
 toList :: T -> Either String [T]
@@ -113,20 +119,20 @@ toList (Fork x rest) = case toList rest of
 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
-formatResult Decode       = decodeResult
+formatT :: EvaluatedForm -> T -> String
+formatT TreeCalculus = toSimpleT . show
+formatT FSL          = show
+formatT AST          = show . toAST
+formatT Ternary      = toTernaryString
+formatT Ascii        = toAscii
+formatT Decode       = decodeResult
 
 toSimpleT :: String -> String
 toSimpleT s = T.unpack
   $ replace "Fork" "t"
   $ replace "Stem" "t"
   $ replace "Leaf" "t"
-  $ (T.pack s)
+  $ T.pack s
 
 toTernaryString :: T -> String
 toTernaryString Leaf = "0"
@@ -153,8 +159,18 @@ toAscii tree = go tree "" True
         ++ go right (prefix ++ (if isLast then "    " else "|   ")) True
 
 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
+decodeResult Leaf = "t"
+decodeResult tc =
+  case (toString tc, toList tc, toNumber tc) of
+    (Right s, _, _) | all isCommonChar s -> "\"" ++ s ++ "\""
+    (_, _, Right n) -> show n
+    (_, Right xs@(_:_), _) -> "[" ++ intercalate ", " (map decodeResult xs) ++ "]"
+    (_, Right [], _) -> "[]"
+    _ -> formatT TreeCalculus tc
+  where
+    isCommonChar c =
+      let n = fromEnum c
+      in (n >= 32 && n <= 126)
+         || n == 9
+         || n == 10
+         || n == 13

test/Spec.hs

@@ -21,8 +21,8 @@ import qualified Data.Set as Set
 main :: IO ()
 main = defaultMain tests
 
-runTricu :: String -> String
-runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
+tricuTestString :: String -> String
+tricuTestString s = show $ result (evalTricu Map.empty $ parseTricu s)
 
 tests :: TestTree
 tests = testGroup "Tricu Tests"
@@ -34,6 +34,7 @@ tests = testGroup "Tricu Tests"
   , fileEval
   , modules
   , demos
+  , decoding
   ]
 
 lexer :: TestTree
@@ -50,7 +51,22 @@ lexer = testGroup "Lexer Tests"
 
   , testCase "Lex escaped characters in strings" $ do
       let input = "\"hello\\nworld\""
-          expect = Right [LStringLiteral "hello\\nworld"]
+          expect = Right [LStringLiteral "hello\nworld"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex multiple escaped characters in strings" $ do
+      let input = "\"tab:\\t newline:\\n quote:\\\" backslash:\\\\\""
+          expect = Right [LStringLiteral "tab:\t newline:\n quote:\" backslash:\\"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex escaped characters in string literals" $ do
+      let input = "x = \"line1\\nline2\\tindented\""
+          expect = Right [LIdentifier "x", LAssign, LStringLiteral "line1\nline2\tindented"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex empty string with escape sequence" $ do
+      let input = "\"\\\"\""
+          expect = Right [LStringLiteral "\""]
       runParser tricuLexer "" input @?= expect
 
   , testCase "Lex mixed literals" $ do
@@ -86,7 +102,7 @@ parser = testGroup "Parser Tests"
         Right _ -> assertFailure "Expected failure when trying to assign the value of T"
 
   , testCase "Parse function definitions" $ do
-      let input = "x = (\\a b c : a)"
+      let input = "x = (a b c : a)"
           expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
       parseSingle input @?= expect
 
@@ -106,7 +122,7 @@ parser = testGroup "Parser Tests"
       parseSingle input @?= expect
 
   , testCase "Parse function with applications" $ do
-      let input  = "f = (\\x : t x)"
+      let input  = "f = (x : t x)"
           expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
       parseSingle input @?= expect
 
@@ -148,22 +164,22 @@ parser = testGroup "Parser Tests"
       parseSingle input @?= expect
 
   , testCase "Parse nested parentheses in function body" $ do
-      let input  = "f = (\\x : t (t (t t)))"
+      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)"
+      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)"
+      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)"
+      let input  = "x = (a : a)\nx (t)"
           expect = [SDef "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
       parseTricu input @?= expect
 
@@ -250,7 +266,7 @@ simpleEvaluation = testGroup "Evaluation Tests"
   , 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)
+      result <- try (evaluate (tricuTestString input)) :: IO (Either SomeException String)
       case result of
         Left  _ -> return ()
         Right _ -> assertFailure "Expected evaluation error"
@@ -258,7 +274,7 @@ simpleEvaluation = testGroup "Evaluation Tests"
 
   , testCase "Apply identity to Boolean Not" $ do
       let not = "(t (t (t t) (t t t)) t)"
-      let input = "x = (\\a : a)\nx " ++ not
+      let input = "x = (a : a)\nx " ++ not
           env = evalTricu Map.empty (parseTricu input)
       result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
   ]
@@ -266,81 +282,85 @@ simpleEvaluation = testGroup "Evaluation Tests"
 lambdas :: TestTree
 lambdas = testGroup "Lambda Evaluation Tests"
   [ testCase "Lambda Identity Function" $ do
-      let input = "id = (\\x : x)\nid t"
-      runTricu input @?= "Leaf"
+      let input = "id = (x : x)\nid t"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda Constant Function (K combinator)" $ do
-      let input = "k = (\\x y : x)\nk t (t t)"
-      runTricu input @?= "Leaf"
+      let input = "k = (x y : x)\nk t (t t)"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda Application with Variable" $ do
-      let input = "id = (\\x : x)\nval = t t\nid val"
-      runTricu input @?= "Stem Leaf"
+      let input = "id = (x : x)\nval = t t\nid val"
+      tricuTestString 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"
+      let input = "apply = (f x y : f x y)\nk = (a b : a)\napply k t (t t)"
+      tricuTestString 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"
+      let input = "apply = (f x y : f x y)\nid = (x : x)\napply (f x : f x) id t"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda with a complex body" $ do
-      let input = "f = (\\x : t (t x))\nf t"
-      runTricu input @?= "Stem (Stem Leaf)"
+      let input = "f = (x : t (t x))\nf t"
+      tricuTestString 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"
+      let input = "f = (x : (y : x))\ng = f t\ng (t t)"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda with Shadowing" $ do
-      let input = "f = (\\x : (\\x : x))\nf t (t t)"
-      runTricu input @?= "Stem Leaf"
+      let input = "f = (x : (x : x))\nf t (t t)"
+      tricuTestString 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"
+      let input = "k = (x : (y : x))\nk_app = k t\nk_app (t t)"
+      tricuTestString input @?= "Leaf"
 
    , testCase "Lambda with free variables" $ do
-      let input = "y = t t\nf = (\\x : y)\nf t"
-      runTricu input @?= "Stem Leaf"
+      let input = "y = t t\nf = (x : y)\nf t"
+      tricuTestString 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)"
+      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)"
+      tricuTestString 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"
+      let input = "f = (a b c : t a b c)\nf t (t t) (t t t)"
+      tricuTestString 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))"
+      let input = "f = (x : t (t (t x)))\nf t"
+      tricuTestString 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)"
+        let input = "f = (x : (y : t x y))\ng = f t\ng (t t)"
+        tricuTestString 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"
+        let input = "id = (x : x)\na = t t\nid a"
+        tricuTestString 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"
+        let input = "f = (x : (y : x y))\ng = (z : z)\nf g t"
+        tricuTestString 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 applied to string literal" $ do
+        let input = "f = (x : x)\nf \"hello\""
+        tricuTestString 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 applied to integer literal" $ do
+        let input = "f = (x : x)\nf 42"
+        tricuTestString 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)"
+   , testCase "Lambda applied to list literal" $ do
+        let input = "f = (x : x)\nf [t (t t)]"
+        tricuTestString input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+
+  , testCase "Lambda containing list literal" $ do
+      let input = "(a : [(a)]) 1"
+      tricuTestString input @?= "Fork (Fork (Stem Leaf) Leaf) Leaf"
   ]
 
 providedLibraries :: TestTree
@@ -414,7 +434,7 @@ providedLibraries = testGroup "Library Tests"
 
   , testCase "List map" $ do
       library <- evaluateFile "./lib/list.tri"
-      let input = "head (tail (map (\\a : (t t t)) [(t) (t) (t)]))"
+      let input = "head (tail (map (a : (t t t)) [(t) (t) (t)]))"
           env = evalTricu library (parseTricu input)
       result env @?= Fork Leaf Leaf
 
@@ -518,3 +538,35 @@ demos = testGroup "Test provided demo functionality"
       res     <- liftIO $ evaluateFileResult "./demos/levelOrderTraversal.tri"
       decodeResult res @?= "\"\n1 \n2 3 \n4 5 6 7 \n8 11 10 9 12 \""
   ]
+
+decoding :: TestTree
+decoding = testGroup "Decoding Tests"
+  [ testCase "Decode Leaf" $ do
+      decodeResult Leaf @?= "t"
+
+  , testCase "Decode list of non-ASCII numbers" $ do
+      let input = ofList [ofNumber 1, ofNumber 14, ofNumber 6]
+      decodeResult input @?= "[1, 14, 6]"
+
+  , testCase "Decode list of ASCII numbers as a string" $ do
+      let input = ofList [ofNumber 97, ofNumber 98, ofNumber 99]
+      decodeResult input @?= "\"abc\""
+
+  , testCase "Decode small number" $ do
+      decodeResult (ofNumber 42) @?= "42"
+
+  , testCase "Decode large number" $ do
+      decodeResult (ofNumber 9999) @?= "9999"
+
+  , testCase "Decode string in list" $ do
+      let input = ofList [ofString "hello", ofString "world"]
+      decodeResult input @?= "[\"hello\", \"world\"]"
+
+  , testCase "Decode mixed list with strings" $ do
+      let input = ofList [ofString "hello", ofNumber 42, ofString "world"]
+      decodeResult input @?= "[\"hello\", 42, \"world\"]"
+
+  , testCase "Decode nested lists with strings" $ do
+      let input = ofList [ofList [ofString "nested"], ofString "string"]
+      decodeResult input @?= "[[\"nested\"], \"string\"]"
+  ]

test/comments-1.tri

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

test/lambda-A.tri

@@ -1 +1 @@
-main = (\x : x) t
+main = (x : x) t

test/map.tri

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

test/size.tri

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

test/string.tri

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

test/vars-B.tri

@@ -1 +1 @@
-y = \x : x
+y = x : x

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.14.0
+version:        0.19.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
@@ -32,6 +32,7 @@ executable tricu
     , megaparsec
     , mtl
     , text
+    , transformers
   other-modules:
     Eval
     FileEval
@@ -63,6 +64,7 @@ test-suite tricu-tests
     , tasty-hunit
     , tasty-quickcheck
     , text
+    , transformers
   default-language:    Haskell2010
   other-modules:
     Eval