# File eval mode now relies on main function

To encourage organizing code in a way that helps in understanding, I
have implemented the common idiom of requiring a `main` function. In
tricu and other functional languages, it is usually placed near the top
of the module. The evaluator gracefully handles the situation of passing
multiple files where the intermediary "library" files do not have main functions.

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

@@ -54,16 +54,12 @@ jobs:
           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
+        uses: akkuman/gitea-release-action@v1
         with:
           files: |-
             ./tricu
-          api_key: '${{ secrets.RELEASE_TOKEN }}'
+          token: '${{ secrets.RELEASE_TOKEN }}'
+          body: '${{ gitea.event.head_commit.message }}'
           pre_release: true

README.md

@@ -2,7 +2,7 @@
 
 ## Introduction
 
-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 (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) terms, but minimal syntax sugar is included to provide a useful programming tool. tricu is under active development and you can expect breaking changes with nearly every commit.
 
 tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
@@ -71,7 +71,7 @@ tricu eval [OPTIONS]
 
   -f --file=FILE  Input file path(s) for evaluation.
                     Defaults to stdin.
-  -t --form=FORM  Optional output form: (tree|fsl|ast|ternary|ascii).
+  -t --form=FORM  Optional output form: (tree|fsl|ast|ternary|ascii|decode).
                     Defaults to tricu-compatible `t` tree form.
 
 tricu decode [OPTIONS]

demos/equality.tri

@@ -1,19 +1,21 @@
+main = lambdaEqualsTC
+
 -- We represent `false` with a Leaf and `true` with a Stem Leaf
-false = t
-true  = t t
+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`
-triage = (\a b c : t (t a b) c)
-matchBool = (\ot 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? = matchBool false true
+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
@@ -25,11 +27,11 @@ not_Lambda? = matchBool false true
 lambdaEqualsTC = equal? not_TC? not_Lambda?
 
 -- Here are some checks to verify their extensional behavior is the same:
-true_TC?  = not_TC? false
-false_TC? = not_TC? true
+true_TC?  = not_TC? demo_false
+false_TC? = not_TC? demo_true
 
-true_Lambda?  = not_Lambda? false
-false_Lambda? = not_Lambda? 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

@@ -1,11 +1,10 @@
+main = exampleTwo
 -- 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`. 
+-- We model labelled binary trees as nested lists where values act as labels. We
+-- require explicit notation of empty nodes. Empty nodes can be represented
+-- with an empty list, `[]`, which evaluates to a single node `t`.
 --
 -- Example tree inputs:
 -- [("1") [("2") [("4") t t] t] [("3") [("5") t t] [("6") t t]]]]
@@ -15,43 +14,42 @@
 --     2   3
 --    /   /  \
 --   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)) 
+  (if (emptyList? (tail node)) 
     [] 
     (head (tail node))))
 
-right = (\node : if (emptyList node) 
+right = (\node : if (emptyList? node) 
   [] 
-  (if (emptyList (tail node)) 
+  (if (emptyList? (tail node)) 
     [] 
-    (if (emptyList (tail (tail node))) 
+    (if (emptyList? (tail (tail 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)) 
       (lconcat (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) 
   "" 
   (lconcat 
     (lconcat (map (\x : lconcat x " ") (head levels)) "") 
-    (if (emptyList (tail levels)) "" (lconcat (t (t 10 t) t) (self (tail levels))))))
+    (if (emptyList? (tail levels)) "" (lconcat (t (t 10 t) t) (self (tail levels))))))
 
-levelOrderToString = (\s : toLineString (levelOrderTraversal_ s))
+levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
 
 flatten = foldl (\acc x : lconcat acc x) ""
 
-levelOrderTraversal = (\s : lconcat (t 10 t) (flatten (levelOrderToString s)))
+levelOrderTraversal = \s : lconcat (t 10 t) (flatten (levelOrderToString s))
 
 exampleOne = levelOrderTraversal [("1") 
                                  [("2") [("4") t t] t] 
@@ -61,5 +59,3 @@ 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

@@ -1,19 +1,21 @@
-compose = (\f g x : f (g x))
+main = size size
 
-succ = y (\self : 
-  triage 
-    1 
-    t 
-    (triage 
-      (t (t t)) 
-      (\_ tail : t t (self tail)) 
+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)) 
+size = (\x :
+  (y (\self x :
+    compose succ
+      (triage
+        (\x : x)
+        self
+        (\x y : compose (self x) (self y))
         x)) x 0))

demos/toSource.tri

@@ -1,3 +1,4 @@
+main = toSource not?
 -- Thanks to intensionality, we can inspect the structure of a given value
 -- even if it's a function. This includes lambdas which are eliminated to
 -- Tree Calculus (TC) terms during evaluation.
@@ -8,7 +9,7 @@
 -- 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)
+-- triage = (\leaf stem fork : t (t leaf stem) fork)
 
 -- Base case of a single Leaf
 sourceLeaf = t (head "t")
@@ -40,7 +41,7 @@ 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)))"

lib/base.tri

@@ -7,37 +7,26 @@ 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)
+id    = \a : 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
 
-triage = (\leaf stem fork : t (t leaf stem) fork)
+y = ((\mut wait fun : wait mut (\x : fun (wait mut x)))
+     (\x : x x)
+     (\a0 a1 a2 : t (t a0) (t t a2) a1))
+
+triage = \leaf stem fork : t (t leaf stem) fork
 test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
 
-matchBool = (\ot of : triage 
-  of 
-  (\_ : ot) 
+matchBool = (\ot of : triage
+  of
+  (\_ : ot)
   (\_ _ : ot)
 )
 
-matchList = (\oe oc : triage 
-  oe 
-  _ 
-  oc
-)
+matchList = \a b : triage a _ b
 
-matchPair = (\op : triage 
-  _ 
-  _ 
-  op
-)
+matchPair = \a   : triage _ _ a
 
 not? = matchBool false true
 and? = matchBool id (\_ : false)
@@ -46,51 +35,49 @@ emptyList? = matchList true (\_ _ : false)
 head = matchList t (\head _ : head)
 tail = matchList t (\_ tail : tail)
 
-lconcat = y (\self : matchList 
-  (\k : k) 
+lconcat = y (\self : matchList
+  (\k : k)
   (\h r k : pair h (self r k)))
 
-lAnd = (triage 
-  (\_     : false) 
-  (\_ x   : x) 
-  (\_ _ x : x)
-)
+lAnd = (triage
+  (\_     : false)
+  (\_ x   : x)
+  (\_ _ x : x))
 
-lOr = (triage 
-  (\x     : x) 
-  (\_ _   : true) 
-  (\_ _ _ : true)
-)
+lOr = (triage
+  (\x     : x)
+  (\_ _   : true)
+  (\_ _ _ : true))
 
-map_ = y (\self : 
-  matchList 
-    (\_ : t) 
+map_ = y (\self :
+  matchList
+    (\_ : t)
     (\head tail f : pair (f head) (self tail f)))
-map = (\f l : map_ l f)
+map = \f l : map_ l f
 
-equal? = y (\self : triage 
-  (triage 
-    true 
-    (\_   : false) 
-    (\_ _ : false)) 
-  (\ax : 
-    triage 
-      false 
-      (self ax) 
-      (\_ _ : false)) 
-  (\ax ay : 
-    triage 
-      false 
-      (\_ : false) 
+equal? = y (\self : triage
+  (triage
+    true
+    (\_   : false)
+    (\_ _ : false))
+  (\ax :
+    triage
+      false
+      (self ax)
+      (\_ _ : false))
+  (\ax ay :
+    triage
+      false
+      (\_ : false)
       (\bx by : lAnd (self ax bx) (self ay by))))
 
-filter_ = y (\self : matchList 
-  (\_ : t) 
+filter_ = y (\self : matchList
+  (\_ : t)
   (\head tail f : matchBool (t head) i (f head) (self tail f)))
-filter  = (\f l : filter_ l 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  = \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  = \f x l : foldr_ x f l

src/Eval.hs

@@ -3,19 +3,19 @@ module Eval where
 import Parser
 import Research
 
+import Data.List (partition)
 import Data.Map  (Map)
-
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 
 evalSingle :: Env -> TricuAST -> Env
 evalSingle env term
-  | SFunc name [] body <- term =
+  | SDef name [] body <- term =
       if
-        | Map.member name env -> 
-            errorWithoutStackTrace $ 
+        | Map.member name env ->
+            errorWithoutStackTrace $
               "Error: Identifier '" ++ name ++ "' is already defined."
-        | otherwise -> 
+        | otherwise ->
             let res = evalAST env body
             in Map.insert "__result" res (Map.insert name res env)
   | SApp func arg <- term =
@@ -23,18 +23,23 @@ evalSingle env term
       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"
+        Just v  ->
+          Map.insert "__result" v env
+        Nothing ->
+          errorWithoutStackTrace $ "Variable `" ++ name ++ "` not defined\n\
+          \This error should never occur here. Please report this as an issue."
   | otherwise =
       Map.insert "__result" (evalAST env term) env
 
 evalTricu :: Env -> [TricuAST] -> Env
-evalTricu env []     = env
-evalTricu env [x]    =
-  let updatedEnv = evalSingle env x
-  in Map.insert "__result" (result updatedEnv) updatedEnv
-evalTricu env (x:xs) =
-  evalTricu (evalSingle env x) xs
+evalTricu env x = go env (reorderDefs env x)
+  where
+    go env []     = env
+    go env [x]    =
+      let updatedEnv = evalSingle env x
+      in Map.insert "__result" (result updatedEnv) updatedEnv
+    go env (x:xs) =
+      evalTricu (evalSingle env x) xs
 
 evalAST :: Env -> TricuAST -> T
 evalAST env term
@@ -54,16 +59,29 @@ evalAST env term
         (errorWithoutStackTrace $ "Variable " ++ name ++ " not defined")
         name env
 
--- https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf
--- Chapter 4: Lambda-Abstraction
 elimLambda :: TricuAST -> TricuAST
 elimLambda = go
   where
+    -- η-reduction
+    go (SLambda [v] (SApp f (SVar x)))
+      | v == x && not (isFree v f) = elimLambda f
+    -- Triage optimization
+    go (SLambda [a] (SLambda [b] (SLambda [c] body)))
+      | body == triageBody         = _TRIAGE
+      where
+        triageBody =
+          (SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c))
+    -- Composition optimization
+    go (SLambda [f] (SLambda [g] (SLambda [x] body)))
+      | body == composeBody        = _COMPOSE
+      where
+        composeBody = SApp (SVar f) (SApp (SVar g) (SVar x))
+    -- General elimination
     go (SLambda (v:vs) body)
-      | null vs              = toSKI v (elimLambda body)
-      | otherwise            = elimLambda (SLambda [v] (SLambda vs body))
-    go (SApp f g)            = SApp (elimLambda f) (elimLambda g)
-    go x                     = x
+      | 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
@@ -73,25 +91,96 @@ 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
+      | otherwise        = errorWithoutStackTrace "Unhandled toSKI conversion"
 
-    _S = parseSingle "t (t (t t t)) t"
-    _K = parseSingle "t t"
-    _I = parseSingle "t (t (t t)) t"
-    
-    isFree x = Set.member x . freeVars
-    freeVars (SVar    v    ) = Set.singleton v
-    freeVars (SInt    _    ) = Set.empty
-    freeVars (SStr    _    ) = Set.empty
-    freeVars (SList   s    ) = foldMap freeVars s
-    freeVars (SApp    f a  ) = freeVars f <> freeVars a
-    freeVars (TLeaf        ) = Set.empty
-    freeVars (SFunc   _ _ 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
+    _S       = parseSingle "t (t (t t t)) t"
+    _K       = parseSingle "t t"
+    _I       = parseSingle "t (t (t t)) t"
+    _TRIAGE  = parseSingle "t (t (t t (t (t (t t t))))) t"
+    _COMPOSE = parseSingle "t (t (t t (t (t (t t t)) t))) (t t)"
+
+isFree :: String -> TricuAST -> Bool
+isFree x = Set.member x . freeVars
+
+freeVars :: TricuAST -> Set.Set String
+freeVars (SVar    v    ) = Set.singleton v
+freeVars (SInt    _    ) = Set.empty
+freeVars (SStr    _    ) = Set.empty
+freeVars (SList   s    ) = foldMap freeVars s
+freeVars (SApp    f a  ) = freeVars f <> freeVars a
+freeVars (TLeaf        ) = Set.empty
+freeVars (SDef   _ _ b) = freeVars b
+freeVars (TStem   t    ) = freeVars t
+freeVars (TFork   l r  ) = freeVars l <> freeVars r
+freeVars (SLambda v b  ) = foldr Set.delete (freeVars b) v
+
+reorderDefs :: Env -> [TricuAST] -> [TricuAST]
+reorderDefs env defs
+  | not (null missingDeps) =
+      errorWithoutStackTrace $
+        "Missing dependencies detected: " ++ show missingDeps
+  | otherwise = orderedDefs ++ others
+  where
+    (defsOnly, others) = partition isDef defs
+    graph              = buildDepGraph defsOnly
+    sortedDefs         = sortDeps graph
+    defMap             = Map.fromList [(name, def) | def@(SDef name _ _) <- defsOnly]
+    orderedDefs        = map (\name -> defMap Map.! name) sortedDefs
+    topDefNames        = Set.fromList (Map.keys defMap)
+    envNames           = Set.fromList (Map.keys env)
+    freeVarsDefs       = foldMap (\(SDef _ _ body) -> freeVars body) defsOnly
+    freeVarsOthers     = foldMap freeVars others
+    allFreeVars        = freeVarsDefs <> freeVarsOthers
+    validNames         = topDefNames `Set.union` envNames
+    missingDeps        = Set.toList (allFreeVars `Set.difference` validNames)
+
+    isDef (SDef _ _ _) = True
+    isDef _            = False
+
+buildDepGraph :: [TricuAST] -> Map.Map String (Set.Set String)
+buildDepGraph topDefs
+  | not (null duplicateNames) =
+      errorWithoutStackTrace $
+        "Duplicate definitions detected: " ++ show duplicateNames
+  | otherwise =
+      Map.fromList
+        [ (name, depends topDefs (SDef name [] body))
+        | SDef name _ body <- topDefs]
+  where
+    names = [name | SDef name _ _ <- topDefs]
+    duplicateNames =
+      [ name | (name, count) <- Map.toList (countOccurrences names) , count > 1]
+    countOccurrences = foldr (\x -> Map.insertWith (+) x 1) Map.empty
+
+sortDeps :: Map.Map String (Set.Set String) -> [String]
+sortDeps graph = go [] (Map.keys graph)
+  where
+    go sorted [] = sorted
+    go sorted remaining
+      | null ready =
+          errorWithoutStackTrace
+            "ERROR: Top-level cyclic dependency detected and prohibited\n\
+           \RESOLVE: Use nested lambdas"
+      | otherwise = go (sorted ++ ready) notReady
+      where
+        ready    = [ name | name <- remaining
+                    , all (`elem` sorted) (Set.toList (graph Map.! name))]
+        notReady =
+          [ name | name <- remaining , name `notElem` ready]
+
+depends :: [TricuAST] -> TricuAST -> Set.Set String
+depends topDefs (SDef _ _ body) =
+  Set.intersection
+    (Set.fromList [n | SDef n _ _ <- topDefs])
+    (freeVars body)
+depends _ _ = Set.empty
 
 result :: Env -> T
 result r = case Map.lookup "__result" r of
   Just a -> a
-  Nothing -> errorWithoutStackTrace "No __result field found in provided environment"
+  Nothing -> errorWithoutStackTrace "No __result field found in provided env"
+
+mainResult :: Env -> T
+mainResult r = case Map.lookup "main" r of
+  Just  a -> a
+  Nothing -> errorWithoutStackTrace "No valid definition for `main` found."

src/FileEval.hs

@@ -13,9 +13,9 @@ evaluateFileResult filePath = do
   contents <- readFile filePath
   let asts = parseTricu contents
   let finalEnv = evalTricu Map.empty asts
-  case Map.lookup "__result" finalEnv of
+  case Map.lookup "main" finalEnv of
     Just finalResult -> return finalResult
-    Nothing -> errorWithoutStackTrace "No expressions to evaluate found"
+    Nothing -> errorWithoutStackTrace "No `main` function detected"
 
 evaluateFile :: FilePath -> IO Env
 evaluateFile filePath = do

src/Main.hs

@@ -1,6 +1,6 @@
 module Main where
 
-import Eval                   (evalTricu, result)
+import Eval                   (evalTricu, mainResult, result)
 import FileEval
 import Parser                 (parseTricu)
 import REPL
@@ -16,7 +16,7 @@ import qualified Data.Map as Map
 data TricuArgs
   = Repl
   | Evaluate { file :: [FilePath], form :: EvaluatedForm }
-  | Decode { file :: [FilePath] }
+  | TDecode { file :: [FilePath] }
   deriving (Show, Data, Typeable)
 
 replMode :: TricuArgs
@@ -31,7 +31,7 @@ evaluateMode = Evaluate
       \ Defaults to stdin."
       &= name "f" &= typ "FILE"
     , form = TreeCalculus &= typ "FORM"
-      &= help "Optional output form: (tree|fsl|ast|ternary|ascii).\n \
+      &= help "Optional output form: (tree|fsl|ast|ternary|ascii|decode).\n \
       \ Defaults to tricu-compatible `t` tree form."
       &= name "t"
   }
@@ -40,7 +40,7 @@ evaluateMode = Evaluate
   &= name "eval"
 
 decodeMode :: TricuArgs
-decodeMode = Decode
+decodeMode = TDecode
   { file = def
     &= help "Optional input file path to attempt decoding.\n \
     \ Defaults to stdin."
@@ -70,10 +70,10 @@ main = do
         (filePath:restFilePaths) -> do
             initialEnv <- evaluateFile filePath
             finalEnv <- foldM evaluateFileWithContext initialEnv restFilePaths
-            pure $ result finalEnv
+            pure $ mainResult finalEnv
       let fRes = formatResult form result
       putStr fRes
-    Decode { file = filePaths } -> do
+    TDecode { file = filePaths } -> do
       value <- case filePaths of
         [] -> getContents
         (filePath:_) -> readFile filePath

src/Parser.hs

@@ -85,13 +85,10 @@ scnParserM :: ParserM ()
 scnParserM = skipMany $ do
   t  <- lookAhead anySingle
   st <- get
-  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
-
+  if | (parenDepth st > 0 || bracketDepth st > 0) && (t == LNewline) ->
+       void $ satisfyM (== LNewline)
+     | otherwise ->
+       fail "In nested context or no space token" <|> empty
 
 eofM :: ParserM ()
 eofM = lift eof
@@ -109,32 +106,23 @@ parseExpressionM = choice
 
 parseFunctionM :: ParserM TricuAST
 parseFunctionM = do
-  LIdentifier name <- satisfyM $ \case
-    LIdentifier _ -> True
-    _             -> False
-  args <- many $ satisfyM $ \case
-    LIdentifier _ -> True
-    _             -> False
+  let ident = (\case LIdentifier _ -> True; _ -> False)
+  LIdentifier name <- satisfyM ident
+  args <- many $ satisfyM ident
   _    <- satisfyM (== LAssign)
   scnParserM
   body <- parseExpressionM
-  pure (SFunc name (map getIdentifier args) body)
+  pure (SDef name (map getIdentifier args) body)
 
 parseLambdaM :: ParserM TricuAST
-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)
+parseLambdaM = do
+  let ident = (\case LIdentifier _ -> True; _ -> False)
+  _      <- satisfyM (== LBackslash)
+  params <- some (satisfyM ident)
+  _      <- satisfyM (== LColon)
+  scnParserM
+  body  <- parseLambdaExpressionM
+  pure $ foldr (\param acc -> SLambda [getIdentifier param] acc) body params
 
 parseLambdaExpressionM :: ParserM TricuAST
 parseLambdaExpressionM = choice
@@ -180,9 +168,8 @@ parseAtomicBaseM = choice
 
 parseTreeLeafM :: ParserM TricuAST
 parseTreeLeafM = do
-  _ <- satisfyM $ \case
-    LKeywordT -> True
-    _         -> False
+  let keyword = (\case LKeywordT -> True; _ -> False)
+  _ <- satisfyM keyword
   notFollowedBy $ lift $ satisfy (== LAssign)
   pure TLeaf
 
@@ -248,37 +235,38 @@ parseGroupedItemM = do
 
 parseSingleItemM :: ParserM TricuAST
 parseSingleItemM = do
-  token <- satisfyM $ \case
-    LIdentifier _ -> True
-    LKeywordT     -> True
-    _             -> False
-  case token of
-    LIdentifier name -> pure (SVar name)
-    LKeywordT        -> pure TLeaf
-    _                -> fail "Unexpected token in list item"
+  token <- satisfyM (\case LIdentifier _ -> True; LKeywordT -> True; _ -> False)
+  if | LIdentifier name <- token -> pure (SVar name)
+     | token == LKeywordT        -> pure TLeaf
+     | otherwise                 -> fail "Unexpected token in list item"
 
 parseVarM :: ParserM TricuAST
 parseVarM = do
-  LIdentifier name <- satisfyM $ \case
-    LIdentifier _ -> True
-    _             -> False
-  if name == "t" || name == "__result"
-    then fail ("Reserved keyword: " ++ name ++ " cannot be assigned.")
-    else pure (SVar name)
+  satisfyM (\case LIdentifier _ -> True; _ -> False) >>= \case
+    LIdentifier name
+      | name == "t" || name == "__result" ->
+        fail ("Reserved keyword: " ++ name ++ " cannot be assigned.")
+      | otherwise                         ->
+         pure (SVar name)
+    _ -> fail "Unexpected token while parsing variable"
 
 parseIntLiteralM :: ParserM TricuAST
 parseIntLiteralM = do
-  LIntegerLiteral value <- satisfyM $ \case
-    LIntegerLiteral _ -> True
-    _                 -> False
-  pure (SInt value)
+  let intL = (\case LIntegerLiteral _ -> True; _ -> False)
+  token <- satisfyM intL
+  if | LIntegerLiteral value <- token ->
+       pure (SInt value)
+     | otherwise                      ->
+       fail "Unexpected token while parsing integer literal"
 
 parseStrLiteralM :: ParserM TricuAST
 parseStrLiteralM = do
-  LStringLiteral value <- satisfyM $ \case 
-    LStringLiteral _ -> True
-    _ -> False
-  pure (SStr value)
+  let strL = (\case LStringLiteral _ -> True; _ -> False)
+  token <- satisfyM strL
+  if | LStringLiteral value <- token ->
+       pure (SStr value)
+     | otherwise                     ->
+       fail "Unexpected token while parsing string literal"
 
 getIdentifier :: LToken -> String
 getIdentifier (LIdentifier name) = name

src/REPL.hs

@@ -59,10 +59,3 @@ repl env = runInputT defaultSettings (loop env)
     
     strip :: String -> String
     strip = dropWhileEnd isSpace . dropWhile isSpace
-
-decodeResult :: T -> String
-decodeResult tc
-  | Right num  <- toNumber tc = show num
-  | Right str  <- toString tc = "\"" ++ str ++ "\""
-  | Right list <- toList tc   = "[" ++ intercalate ", " (map decodeResult list) ++ "]"
-  | otherwise                 = formatResult TreeCalculus tc

src/Research.hs

@@ -19,7 +19,7 @@ data TricuAST
   | SInt Int
   | SStr String
   | SList [TricuAST]
-  | SFunc String [String] TricuAST
+  | SDef String [String] TricuAST
   | SApp TricuAST TricuAST
   | TLeaf
   | TStem TricuAST
@@ -45,7 +45,7 @@ data LToken
   deriving (Show, Eq, Ord)
 
 -- Output formats
-data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii
+data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii | Decode
   deriving (Show, Data, Typeable)
 
 -- Environment containing previously evaluated TC terms
@@ -115,6 +115,7 @@ formatResult FSL          = show
 formatResult AST          = show . toAST
 formatResult Ternary      = toTernaryString
 formatResult Ascii        = toAscii
+formatResult Decode       = decodeResult
 
 toSimpleT :: String -> String
 toSimpleT s = T.unpack 
@@ -147,4 +148,9 @@ toAscii tree = go tree "" True
         ++ go left (prefix ++ (if isLast then "    " else "|   ")) False
         ++ go right (prefix ++ (if isLast then "    " else "|   ")) True
 
--- Utility
+decodeResult :: T -> String
+decodeResult tc
+  | Right num  <- toNumber tc = show num
+  | Right str  <- toString tc = "\"" ++ str ++ "\""
+  | Right list <- toList tc   = "[" ++ intercalate ", " (map decodeResult list) ++ "]"
+  | otherwise                 = formatResult TreeCalculus tc

test/Spec.hs

@@ -25,16 +25,17 @@ 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"]
@@ -74,8 +75,8 @@ lexerTests = testGroup "Lexer Tests"
           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
@@ -84,7 +85,7 @@ parserTests = testGroup "Parser Tests"
 
   , testCase "Parse function definitions" $ do
       let input = "x = (\\a b c : a)"
-          expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
+          expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
       parseSingle input @?= expect
 
   , testCase "Parse nested Tree Calculus terms" $ do
@@ -104,7 +105,7 @@ parserTests = testGroup "Parser Tests"
 
   , testCase "Parse function with applications" $ do
       let input  = "f = (\\x : t x)"
-          expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
+          expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
       parseSingle input @?= expect
 
   , testCase "Parse nested lists" $ do
@@ -146,7 +147,7 @@ parserTests = testGroup "Parser Tests"
 
   , testCase "Parse nested parentheses in function body" $ do
       let input  = "f = (\\x : t (t (t t)))"
-          expect = SFunc "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
+          expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
       parseSingle input @?= expect
 
   , testCase "Parse lambda abstractions" $ do
@@ -156,12 +157,12 @@ parserTests = testGroup "Parser Tests"
 
   , testCase "Parse multiple arguments to lambda abstractions" $ do
       let input  = "x = (\\a b : a)"
-          expect = SFunc "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
+          expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
       parseSingle input @?= expect
 
   , testCase "Grouping T terms with parentheses in function application" $ do
       let input  = "x = (\\a : a)\nx (t)"
-          expect = [SFunc "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
+          expect = [SDef "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
       parseTricu input @?= expect
 
   , testCase "Comments 1" $ do
@@ -175,8 +176,8 @@ parserTests = testGroup "Parser Tests"
       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
@@ -244,7 +245,7 @@ evaluationTests = testGroup "Evaluation Tests"
       (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 <- try (evaluate (runTricu input)) :: IO (Either SomeException String)
@@ -260,8 +261,8 @@ 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"
@@ -340,8 +341,8 @@ lambdaEvalTests = testGroup "Lambda Evaluation Tests"
         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)"
@@ -476,8 +477,8 @@ libraryTests = testGroup "Library Tests"
       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
@@ -487,11 +488,32 @@ fileEvaluationTests = testGroup "Evaluation tests"
       res @?= Fork (Stem Leaf) Leaf
 
   , testCase "Mapping and Equality" $ do
-      res <- liftIO $ evaluateFileResult "./test/map.tri"
-      res @?= Stem Leaf
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      fEnv    <- liftIO $ evaluateFileWithContext library "./test/map.tri"
+      (mainResult fEnv) @?= Stem Leaf
 
   , testCase "Eval and decoding string" $ do
       library <- liftIO $ evaluateFile "./lib/base.tri"
       res <- liftIO $ evaluateFileWithContext library "./test/string.tri"
       decodeResult (result res) @?= "\"String test!\""
   ]
+
+demos :: TestTree
+demos = testGroup "Test provided demo functionality"
+  [ testCase "Structural equality demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/equality.tri"
+      decodeResult (result res) @?= "t t"
+  , testCase "Convert values back to source code demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/toSource.tri"
+      decodeResult (result res) @?= "\"(t (t (t t) (t t t)) (t t (t t t)))\""
+  , testCase "Determining the size of functions" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/size.tri"
+      decodeResult (result res) @?= "454"
+  , testCase "Level Order Traversal demo" $ do
+      library <- liftIO $ evaluateFile "./lib/base.tri"
+      res     <- liftIO $ evaluateFileWithContext library "./demos/levelOrderTraversal.tri"
+      decodeResult (result res) @?= "\"\n1 \n2 3 \n4 5 6 7 \n8 11 10 9 12 \""
+  ]

test/comments-1.tri

@@ -2,7 +2,7 @@
 -- t (t t) (t (t t t))
 -- t (t t t) (t t)
 -- x = (\a : a)
-t (t t) t -- Fork (Stem Leaf) Leaf
+main = t (t t) t -- Fork (Stem Leaf) Leaf
 -- t t
 -- x
 -- x = (\a : a)

test/fork.tri

@@ -1 +1 @@
-t t t 
+main = t t t 

test/map.tri

@@ -1,24 +1,2 @@
-false = t
-true = t t
-_ = t
-k = t t
-i = t (t k) t
-s = t (t (k t)) t
-m = s i i
-b = s (k s) k
-c = s (s (k s) (s (k k) s)) (k k)
-iC = (\a b c : s a (k c) b)
-yi = (\i : b m (c b (i m)))
-y = yi iC
-triage = (\a b c : t (t a b) c)
-pair = t
-matchList = (\oe oc : triage oe _ oc)
-lconcat = y (\self : matchList (\k : k) (\h r k : pair h (self r k)))
-hmap = y (\self : matchList (\f : t) (\hd tl f : pair (f hd) (self tl f)))
-map = (\f l : hmap l f)
-lAnd = triage (\x : false) (\_ x : x) (\_ _ x : x)
-lOr = triage (\x : x) (\_ _ : true) (\_ _ x : true)
-equal = y (\self : triage (triage true (\z : false) (\y z : false)) (\ax : triage false (self ax) (\y z : false)) (\ax ay : triage false (\z : false) (\bx by : lAnd (self ax bx) (self ay by))))
-
 x = map (\i : lconcat "Successfully concatenated " i) [("two strings!")]
-equal x [("Successfully concatenated two strings!")]
+main = equal? x [("Successfully concatenated two strings!")]

test/size.tri

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

test/undefined.tri

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

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.7.0
+version:        0.11.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co