Allow lambda expressions without explicit paren

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)`.
 

demos/equality.tri

@@ -6,7 +6,7 @@ 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_triage = \a b c : t (t a b) c
 demo_matchBool = (\ot of : demo_triage
   of
   (\_ : ot)

demos/levelOrderTraversal.tri

@@ -17,9 +17,9 @@
 --   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)) 
     [] 
@@ -39,7 +39,7 @@ processLevel = y (\self queue : if (emptyList? queue)
     (\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) 
   "" 
@@ -47,11 +47,11 @@ toLineString = y (\self levels : if (emptyList? levels)
     (lconcat (map (\x : lconcat x " ") (head levels)) "") 
     (if (emptyList? (tail levels)) "" (lconcat (t (t 10 t) t) (self (tail levels))))))
 
-levelOrderToString = (\s : toLineString (levelOrderTraversal_ s))
+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] 

demos/size.tri

@@ -1,4 +1,4 @@
-compose = (\f g x : f (g x))
+compose = \f g x : f (g x)
 
 succ = y (\self : 
   triage 

demos/toSource.tri

@@ -40,7 +40,7 @@ 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

@@ -7,15 +7,15 @@ s     = t (t (k t)) t
 m     = s i i
 b     = s (k s) k
 c     = s (s (k s) (s (k k) s)) (k k)
-id    = (\a : a)
+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
 
 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)
+triage = \leaf stem fork : t (t leaf stem) fork
 test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
 
 matchBool = (\ot of : triage 
@@ -24,17 +24,9 @@ matchBool = (\ot of : triage
   (\_ _ : ot)
 )
 
-matchList = (\oe oc : triage 
+matchList = \a b : triage a _ b
-  oe 
-  _ 
-  oc
-)
 
-matchPair = (\op : triage 
+matchPair = \a   : triage _ _ a
-  _ 
-  _ 
-  op
-)
 
 not? = matchBool false true
 and? = matchBool id (\_ : false)
@@ -50,20 +42,18 @@ lconcat = y (\self : matchList
 lAnd = (triage 
   (\_     : false) 
   (\_ x   : x) 
-  (\_ _ x : x)
+  (\_ _ x : x))
-)
 
 lOr = (triage 
   (\x     : x) 
   (\_ _   : true) 
-  (\_ _ _ : true)
+  (\_ _ _ : true))
-)
 
 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 
@@ -84,10 +74,10 @@ equal? = y (\self : triage
 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

@@ -54,8 +54,6 @@ 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
@@ -68,9 +66,9 @@ elimLambda = go
       where
         triageBody =
           (SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c))
-    -- Compose optimization
+    -- Composition optimization
     go (SLambda [f] (SLambda [g] (SLambda [x] body))) 
-      | body == composeBody = _COMPOSE
+      | body == composeBody        = _COMPOSE
       where
         composeBody = SApp (SVar f) (SApp (SVar g) (SVar x))
     -- General elimination

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

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.7.0
+version:        0.9.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co