Definition dependency analysis

tricu now allows defining terms in any order and will resolve
dependencies to ensure that they're evaluated in the right order.
Undefined terms are detected and throw errors during dependency
ordering.
For now we can't define top-level mutually recursive terms.

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

@@ -1,19 +1,19 @@
 -- We represent `false` with a Leaf and `true` with a Stem Leaf
-false = t
+demo_false = t
-true  = t 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)
+demo_triage = \a b c : t (t a b) c
-matchBool = (\ot of : triage
+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 +25,11 @@ 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
+true_TC?  = not_TC? demo_false
-false_TC? = not_TC? true
+false_TC? = not_TC? demo_true
 
-true_Lambda?  = not_Lambda? false
+true_Lambda?  = not_Lambda? demo_false
-false_Lambda? = not_Lambda? true
+false_Lambda? = not_Lambda? demo_true
 
 bothTrueEqual?  = equal? true_TC?  true_Lambda?
 bothFalseEqual? = equal? false_TC? false_Lambda?

demos/levelOrderTraversal.tri

@@ -1,11 +1,9 @@
 -- 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
--- 
--- 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`. 
+-- 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 +13,42 @@
 --     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] 

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
@@ -17,3 +17,5 @@ size = (\x :
         self
         (\x y : compose (self x) (self y))
         x)) x 0))
+
+size size

demos/toSource.tri

@@ -8,7 +8,7 @@
 -- 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 +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

@@ -7,18 +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)
-iC    = (\a b c : s a (k c) b)
+id    = \a : a
-iD    = b (b iC) iC
-iE    = b (b iD) iC
-yi    = (\i : b m (c b (i m)))
-y     = yi iC
-yC    = yi iD
-yD    = yi iE
-id    = (\a : a)
 pair  = t
-if    = (\cond then else : t (t else (t t then)) t cond)
+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
@@ -27,17 +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)
@@ -53,20 +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
@@ -87,10 +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

@@ -3,14 +3,14 @@ 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 $
@@ -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
@@ -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)
+      | null vs                    = toSKI v (elimLambda body)
-      | otherwise            = elimLambda (SLambda [v] (SLambda vs body))
+      | otherwise                  = elimLambda (SLambda [v] (SLambda vs body))
-    go (SApp f g)            = SApp (elimLambda f) (elimLambda g)
+    go (SApp f g)                  = SApp (elimLambda f) (elimLambda g)
-    go x                     = x
+    go x                           = x
 
     toSKI x (SVar y)
       | x == y           = _I
@@ -73,25 +91,91 @@ 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"
+    _S       = parseSingle "t (t (t t t)) t"
-    _K = parseSingle "t t"
+    _K       = parseSingle "t t"
-    _I = parseSingle "t (t (t 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 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"

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)
+  pure (SDef 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

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

test/Spec.hs

@@ -25,16 +25,17 @@ runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
 
 tests :: TestTree
 tests = testGroup "Tricu Tests"
-  [ lexerTests
+  [ lexer
-  , parserTests
+  , parser
-  , evaluationTests
+  , simpleEvaluation
-  , lambdaEvalTests
+  , lambdas
-  , libraryTests
+  , baseLibrary
-  , fileEvaluationTests
+  , fileEval
+  , demos
   ]
 
-lexerTests :: TestTree
+lexer :: TestTree
-lexerTests = testGroup "Lexer Tests"
+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
+parser :: TestTree
-parserTests = testGroup "Parser Tests"
+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
+simpleEvaluation :: TestTree
-evaluationTests = testGroup "Evaluation Tests"
+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
+lambdas :: TestTree
-lambdaEvalTests = testGroup "Lambda Evaluation Tests"
+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
+baseLibrary :: TestTree
-libraryTests = testGroup "Library Tests"
+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
+fileEval :: TestTree
-fileEvaluationTests = testGroup "Evaluation tests"
+fileEval = testGroup "File evaluation tests"
   [ testCase "Forks" $ do
       res <- liftIO $ evaluateFileResult "./test/fork.tri"
       res @?= Fork Leaf Leaf
@@ -495,3 +496,23 @@ fileEvaluationTests = testGroup "Evaluation tests"
       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/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:        0.10.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co