# 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

@@ -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

@@ -1,3 +1,5 @@
+main = lambdaEqualsTC
+
 -- We represent `false` with a Leaf and `true` with a Stem Leaf
 demo_false = t
 demo_true  = t t

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 nested lists where values act as labels. We
--- 
+-- require explicit notation of empty nodes. Empty nodes can be represented
--- We model labelled binary trees as sublists where values act as labels. We
+-- with an empty list, `[]`, which evaluates to a single node `t`.
--- require explicit not?ation of empty nodes. Empty nodes can be represented 
--- with an empty list, `[]`, which is equivalent to a single node `t`. 
 --
 -- Example tree inputs:
 -- [("1") [("2") [("4") t t] t] [("3") [("5") t t] [("6") t t]]]]
@@ -15,7 +14,6 @@
 --     2   3
 --    /   /  \
 --   4   5    6
---
 
 label = \node : head node
 
@@ -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

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

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.

lib/base.tri

@@ -18,9 +18,9 @@ y = ((\mut wait fun : wait mut (\x : fun (wait mut x)))
 triage = \leaf stem fork : t (t leaf stem) fork
 test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
 
-matchBool = (\ot of : triage 
+matchBool = (\ot of : triage
-  of 
+  of
-  (\_ : ot) 
+  (\_ : ot)
   (\_ _ : ot)
 )
 
@@ -35,44 +35,44 @@ emptyList? = matchList true (\_ _ : false)
 head = matchList t (\head _ : head)
 tail = matchList t (\_ tail : tail)
 
-lconcat = y (\self : matchList 
+lconcat = y (\self : matchList
-  (\k : k) 
+  (\k : k)
   (\h r k : pair h (self r k)))
 
-lAnd = (triage 
+lAnd = (triage
-  (\_     : false) 
+  (\_     : false)
-  (\_ x   : x) 
+  (\_ x   : x)
   (\_ _ x : x))
 
-lOr = (triage 
+lOr = (triage
-  (\x     : x) 
+  (\x     : x)
-  (\_ _   : true) 
+  (\_ _   : true)
   (\_ _ _ : true))
 
-map_ = y (\self : 
+map_ = y (\self :
-  matchList 
+  matchList
-    (\_ : t) 
+    (\_ : t)
     (\head tail f : pair (f head) (self tail f)))
 map = \f l : map_ l f
 
-equal? = y (\self : triage 
+equal? = y (\self : triage
-  (triage 
+  (triage
-    true 
+    true
-    (\_   : false) 
+    (\_   : false)
-    (\_ _ : false)) 
+    (\_ _ : false))
-  (\ax : 
+  (\ax :
-    triage 
+    triage
-      false 
+      false
-      (self ax) 
+      (self ax)
-      (\_ _ : false)) 
+      (\_ _ : false))
-  (\ax ay : 
+  (\ax ay :
-    triage 
+    triage
-      false 
+      false
-      (\_ : false) 
+      (\_ : false)
       (\bx by : lAnd (self ax bx) (self ay by))))
 
-filter_ = y (\self : matchList 
+filter_ = y (\self : matchList
-  (\_ : t) 
+  (\_ : t)
   (\head tail f : matchBool (t head) i (f head) (self tail f)))
 filter  = \f l : filter_ l f
 

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 -> 
+        | Map.member name env ->
-            errorWithoutStackTrace $ 
+            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
+        Just v  ->
-        Nothing -> errorWithoutStackTrace $ "Variable `" ++ name ++ "` not defined"
+          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 = go env (reorderDefs env x)
-evalTricu env [x]    =
+  where
-  let updatedEnv = evalSingle env x
+    go env []     = env
-  in Map.insert "__result" (result updatedEnv) updatedEnv
+    go env [x]    =
-evalTricu env (x:xs) =
+      let updatedEnv = evalSingle env x
-  evalTricu (evalSingle env x) xs
+      in Map.insert "__result" (result updatedEnv) updatedEnv
+    go env (x:xs) =
+      evalTricu (evalSingle env x) xs
 
 evalAST :: Env -> TricuAST -> T
 evalAST env term
@@ -61,13 +66,13 @@ elimLambda = go
     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))) 
+    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))) 
+    go (SLambda [f] (SLambda [g] (SLambda [x] body)))
       | body == composeBody        = _COMPOSE
       where
         composeBody = SApp (SVar f) (SApp (SVar g) (SVar x))
@@ -93,20 +98,89 @@ elimLambda = go
     _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 x = Set.member x . freeVars
+isFree :: String -> TricuAST -> Bool
-    freeVars (SVar    v    ) = Set.singleton v
+isFree x = Set.member x . freeVars
-    freeVars (SInt    _    ) = Set.empty
+
-    freeVars (SStr    _    ) = Set.empty
+freeVars :: TricuAST -> Set.Set String
-    freeVars (SList   s    ) = foldMap freeVars s
+freeVars (SVar    v    ) = Set.singleton v
-    freeVars (SApp    f a  ) = freeVars f <> freeVars a
+freeVars (SInt    _    ) = Set.empty
-    freeVars (TLeaf        ) = Set.empty
+freeVars (SStr    _    ) = Set.empty
-    freeVars (SFunc   _ _ b) = freeVars b
+freeVars (SList   s    ) = foldMap freeVars s
-    freeVars (TStem   t    ) = freeVars t
+freeVars (SApp    f a  ) = freeVars f <> freeVars a
-    freeVars (TFork   l r  ) = freeVars l <> freeVars r
+freeVars (TLeaf        ) = Set.empty
-    freeVars (SLambda v b  ) = foldr Set.delete (freeVars b) v
+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

@@ -112,7 +112,7 @@ parseFunctionM = do
   _    <- satisfyM (== LAssign)
   scnParserM
   body <- parseExpressionM
-  pure (SFunc name (map getIdentifier args) body)
+  pure (SDef name (map getIdentifier args) body)
 
 parseLambdaM :: ParserM TricuAST
 parseLambdaM = do

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

@@ -85,7 +85,7 @@ parser = 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
@@ -105,7 +105,7 @@ parser = 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
@@ -147,7 +147,7 @@ parser = 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
@@ -157,12 +157,12 @@ parser = 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
@@ -488,8 +488,9 @@ fileEval = testGroup "File evaluation tests"
       res @?= Fork (Stem Leaf) Leaf
 
   , testCase "Mapping and Equality" $ do
-      res <- liftIO $ evaluateFileResult "./test/map.tri"
+      library <- liftIO $ evaluateFile "./lib/base.tri"
-      res @?= Stem Leaf
+      fEnv    <- liftIO $ evaluateFileWithContext library "./test/map.tri"
+      (mainResult fEnv) @?= Stem Leaf
 
   , testCase "Eval and decoding string" $ do
       library <- liftIO $ evaluateFile "./lib/base.tri"

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:        0.9.0
+version:        0.11.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co