Support for list literals in Lambdas

Adds support for REPL namespacing, primarily to avoid `main` collisions.
Also adds a library function for an ergonomic pattern matching function
that I've been noodling on. I might explore ways to make list syntax
less annoying specifically for pattern matching like this.

.gitignore

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

README.md

@@ -2,7 +2,9 @@
 
 ## 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 is under active development and you can expect breaking changes with nearly every commit.
+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 should expect breaking changes with every commit.*
 
 tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
@@ -14,7 +16,7 @@ tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)
 - Lambda abstraction syntax: `id = (\a : a)`
 - List, Number, and String literals: `[(2) ("Hello")]` 
 - Function application: `not (not false)`
-- Higher order/first-class functions: `map (\a : lconcat a "!") [("Hello")]`
+- Higher order/first-class functions: `map (\a : append a "!") [("Hello")]`
 - Intensionality blurs the distinction between functions and data (see REPL examples)
 - Simple module system for code organization
 
@@ -23,9 +25,9 @@ tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)
 ```
 tricu < -- Anything after `--` on a single line is a comment
 tricu < id = (\a : a) -- Lambda abstraction is eliminated to tree calculus terms
-tricu < head (map (\i : lconcat i " world!") [("Hello, ")])
+tricu < head (map (\i : append i " world!") [("Hello, ")])
 tricu > "Hello,  world!"
-tricu < id (head (map (\i : lconcat i " world!") [("Hello, ")]))
+tricu < id (head (map (\i : append i " world!") [("Hello, ")]))
 tricu > "Hello,  world!"
 
 tricu < -- Intensionality! We can inspect the structure of a function or data.

demos/equality.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = lambdaEqualsTC
 

demos/levelOrderTraversal.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" Lib
+!import "../lib/list.tri" !Local
 
 main = exampleTwo
 -- Level Order Traversal of a labelled binary tree
@@ -37,21 +38,21 @@ processLevel = y (\self queue : if (emptyList? queue)
   [] 
   (pair (map label queue) (self (filter 
     (\node : not? (emptyList? node)) 
-      (lconcat (map left queue) (map right queue))))))
+      (append (map left queue) (map right queue))))))
 
 levelOrderTraversal_ = \a : processLevel (t a t)
 
 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))))))
+  (append 
+    (append (map (\x : append x " ") (head levels)) "") 
+    (if (emptyList? (tail levels)) "" (append (t (t 10 t) t) (self (tail levels))))))
 
 levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
 
-flatten = foldl (\acc x : lconcat acc x) ""
+flatten = foldl (\acc x : append acc x) ""
 
-levelOrderTraversal = \s : lconcat (t 10 t) (flatten (levelOrderToString s))
+levelOrderTraversal = \s : append (t 10 t) (flatten (levelOrderToString s))
 
 exampleOne = levelOrderTraversal [("1") 
                                  [("2") [("4") t t] t] 

demos/size.tri

@@ -1,18 +1,8 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = size size
 
-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

demos/toSource.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = toSource not?
 -- Thanks to intensionality, we can inspect the structure of a given value

flake.nix

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

lib/base.tri

@@ -1,13 +1,8 @@
 false = t
 _     = t
 true  = 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)
 id    = \a : a
+const = \a b : a
 pair  = t
 if    = \cond then else : t (t else (t t then)) t cond
 
@@ -15,6 +10,8 @@ y = ((\mut wait fun : wait mut (\x : fun (wait mut x)))
      (\x : x x)
      (\a0 a1 a2 : t (t a0) (t t a2) a1))
 
+compose = \f g x : f (g x)
+
 triage = \leaf stem fork : t (t leaf stem) fork
 test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
 
@@ -24,21 +21,6 @@ matchBool = (\ot of : triage
   (\_ _ : ot)
 )
 
-matchList = \a b : triage a _ b
-
-matchPair = \a   : triage _ _ a
-
-not? = matchBool false true
-and? = matchBool id (\_ : false)
-emptyList? = matchList true (\_ _ : false)
-
-head = matchList t (\head _ : head)
-tail = matchList t (\_ tail : tail)
-
-lconcat = y (\self : matchList
-  (\k : k)
-  (\h r k : pair h (self r k)))
-
 lAnd = (triage
   (\_     : false)
   (\_ x   : x)
@@ -49,11 +31,22 @@ lOr = (triage
   (\_ _   : true)
   (\_ _ _ : true))
 
-map_ = y (\self :
-  matchList
-    (\_ : t)
-    (\head tail f : pair (f head) (self tail f)))
-map = \f l : map_ l f
+matchPair = \a : triage _ _ a
+
+not? = matchBool false true
+and? = matchBool id (\_ : false)
+
+or? = (\x z : 
+  matchBool 
+    (matchBool true true z)
+    (matchBool true false z)
+    x)
+
+xor? = (\x z : 
+  matchBool 
+    (matchBool false true z)
+    (matchBool true false z)
+    x)
 
 equal? = y (\self : triage
   (triage
@@ -71,13 +64,11 @@ equal? = y (\self : triage
       (\_ : false)
       (\bx by : lAnd (self ax bx) (self ay by))))
 
-filter_ = y (\self : matchList
-  (\_ : t)
-  (\head tail f : matchBool (t head) i (f head) (self tail f)))
-filter  = \f l : filter_ l f
-
-foldl_ = y (\self f l x : matchList (\acc : acc) (\head tail acc : self f tail (f acc head)) l x)
-foldl  = \f x l : foldl_ f l x
-
-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
+succ = y (\self :
+  triage
+    1
+    t
+    (triage
+      (t (t t))
+      (\_ tail : t t (self tail))
+      t))

lib/list.tri

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

lib/patterns.tri

@@ -0,0 +1,35 @@
+!import "list.tri" !Local
+
+match_ = y (\self value patterns :
+  triage
+    t
+    (\_ : t)
+    (\pattern rest :
+      triage
+        t
+        (\_ : t)
+        (\test result :
+          if (test value)
+             (result value)
+             (self value rest))
+        pattern)
+    patterns)
+
+match = (\value patterns :
+  match_ value (map (\sublist :
+    pair (head sublist) (head (tail sublist)))
+    patterns))
+
+otherwise = const (t t)
+
+-- matchExample = (\x : match x [[(equal? 1)  (\_ : "one")]
+--                               [(equal? 2)  (\_ : "two")]
+--                               [(equal? 3)  (\_ : "three")]
+--                               [(equal? 4)  (\_ : "four")]
+--                               [(equal? 5)  (\_ : "five")]
+--                               [(equal? 6)  (\_ : "six")]
+--                               [(equal? 7)  (\_ : "seven")]
+--                               [(equal? 8)  (\_ : "eight")]
+--                               [(equal? 9)  (\_ : "nine")]
+--                               [(equal? 10) (\_ : "ten")]
+--                               [ otherwise  (\_ : "I ran out of fingers!")]])

src/Eval.hs

@@ -19,16 +19,16 @@ evalSingle env term
       Nothing ->
         let res = evalAST env body
         in Map.insert "!result" res (Map.insert name res env)
-  | SApp func arg <- term 
+  | SApp func arg <- term
   = let res = apply (evalAST env func) (evalAST env arg)
       in Map.insert "!result" res env
-  | SVar name <- term 
+  | SVar name <- term
   = case Map.lookup name env of
         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 
+  | otherwise
   = Map.insert "!result" (evalAST env term) env
 
 evalTricu :: Env -> [TricuAST] -> Env
@@ -74,9 +74,10 @@ elimLambda = go
     -- Composition optimization
     go (SLambda [f] (SLambda [g] (SLambda [x] body)))
       | body == SApp (SVar f) (SApp (SVar g) (SVar x)) = _B
-    go (SLambda [f] (SLambda [x] (SLambda [y] body)))
-      | body == SApp (SApp (SVar f) (SVar y)) (SVar x) = _C
     -- General elimination
+    go (SLambda [v] (SList xs))
+      = elimLambda (SLambda [v] (foldr wrapTLeaf TLeaf xs))
+        where wrapTLeaf m r = SApp (SApp TLeaf m) r
     go (SLambda (v:vs) body)
       | null vs                    = toSKI v (elimLambda body)
       | otherwise                  = elimLambda (SLambda [v] (SLambda vs body))
@@ -97,7 +98,6 @@ elimLambda = go
     _K       = parseSingle "t t"
     _I       = parseSingle "t (t (t t)) t"
     _B       = parseSingle "t (t (t t (t (t (t t t)) t))) (t t)"
-    _C       = parseSingle "t (t (t (t (t t (t (t (t t t)) t))) (t (t (t t (t t))) (t (t (t t t)) t)))) (t t (t t))"
     _TRIAGE  = parseSingle "t (t (t t (t (t (t t t))))) t"
 
 isFree :: String -> TricuAST -> Bool
@@ -144,18 +144,23 @@ reorderDefs env defs
 
 buildDepGraph :: [TricuAST] -> Map.Map String (Set.Set String)
 buildDepGraph topDefs
-  | not (null duplicateNames) =
+  | not (null conflictingDefs) =
       errorWithoutStackTrace $
-        "Duplicate definitions detected: " ++ show duplicateNames
+        "Conflicting definitions detected: " ++ show conflictingDefs
   | 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
+    defsMap = Map.fromListWith (++)
+      [(name, [(name, body)]) | SDef name _ body <- topDefs]
+
+    conflictingDefs =
+      [ name
+      | (name, defs) <- Map.toList defsMap
+      , let bodies = map snd defs
+      , not $ all (== head bodies) (tail bodies)
+      ]
 
 sortDeps :: Map.Map String (Set.Set String) -> [String]
 sortDeps graph = go [] Set.empty (Map.keys graph)

src/FileEval.hs

@@ -6,12 +6,34 @@ import Parser
 import Research
 
 import Data.List       (partition)
+import Data.Maybe      (mapMaybe)
 import Control.Monad   (foldM)
 import System.IO
+import System.FilePath (takeDirectory, normalise, (</>))
 
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 
+extractMain :: Env -> Either String T
+extractMain env =
+  case Map.lookup "main" env of
+    Just result -> Right result
+    Nothing -> Left "No `main` function detected"
+
+processImports :: Set.Set FilePath -> FilePath -> FilePath -> [TricuAST]
+                 -> Either String ([TricuAST], [(FilePath, String, FilePath)])
+processImports seen base currentPath asts =
+  let (imports, nonImports) = partition isImp asts
+      importPaths = mapMaybe getImportInfo imports
+  in if currentPath `Set.member` seen
+     then Left $ "Encountered cyclic import: " ++ currentPath
+     else Right (nonImports, importPaths)
+  where
+    isImp (SImport _ _) = True
+    isImp _ = False
+    getImportInfo (SImport p n) = Just (p, n, makeRelativeTo currentPath p)
+    getImportInfo _ = Nothing
+
 evaluateFileResult :: FilePath -> IO T
 evaluateFileResult filePath = do
   contents <- readFile filePath
@@ -19,11 +41,11 @@ evaluateFileResult filePath = do
   case parseProgram tokens of
     Left err -> errorWithoutStackTrace (handleParseError err)
     Right ast -> do
-      ast <- preprocessFile filePath
-      let finalEnv = evalTricu Map.empty ast
-      case Map.lookup "main" finalEnv of
-        Just finalResult -> return finalResult
-        Nothing -> errorWithoutStackTrace "No `main` function detected"
+      processedAst <- preprocessFile filePath
+      let finalEnv = evalTricu Map.empty processedAst
+      case extractMain finalEnv of
+        Right result -> return result
+        Left err -> errorWithoutStackTrace err
 
 evaluateFile :: FilePath -> IO Env
 evaluateFile filePath = do
@@ -46,37 +68,33 @@ evaluateFileWithContext env filePath = do
       pure $ evalTricu env ast
 
 preprocessFile :: FilePath -> IO [TricuAST]
-preprocessFile = preprocessFile' Set.empty
+preprocessFile p = preprocessFile' Set.empty p p
 
-preprocessFile' :: Set.Set FilePath -> FilePath -> IO [TricuAST]
-preprocessFile' inProgress filePath
-  | filePath `Set.member` inProgress = 
-      errorWithoutStackTrace $ "Encountered cyclic import: " ++ filePath
-  | otherwise = do
-      contents <- readFile filePath
-      let tokens = lexTricu contents
-      case parseProgram tokens of
-        Left err -> errorWithoutStackTrace (handleParseError err)
-        Right asts -> do
-          let (imports, nonImports) = partition isImport asts
-          let newInProgress = Set.insert filePath inProgress
-          importedASTs <- concat <$> mapM (processImport newInProgress "") imports
-          pure $ importedASTs ++ nonImports
+preprocessFile' :: Set.Set FilePath -> FilePath -> FilePath -> IO [TricuAST]
+preprocessFile' seen base currentPath = do
+  contents <- readFile currentPath
+  let tokens = lexTricu contents
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right ast ->
+      case processImports seen base currentPath ast of
+        Left err -> errorWithoutStackTrace err
+        Right (nonImports, importPaths) -> do
+          let seen' = Set.insert currentPath seen
+          imported <- concat <$> mapM (processImportPath seen' base) importPaths
+          pure $ imported ++ nonImports
   where
-    isImport :: TricuAST -> Bool
-    isImport (SImport _ _) = True
-    isImport _             = False
+    processImportPath seen base (path, name, importPath) = do
+      ast <- preprocessFile' seen base importPath
+      pure $ map (nsDefinition (if name == "!Local" then "" else name))
+           $ filter (not . isImp) ast
+    isImp (SImport _ _) = True
+    isImp _ = False
 
-    processImport :: Set.Set FilePath -> String -> TricuAST -> IO [TricuAST]
-    processImport prog currentModule (SImport path "!Local") = do
-      ast <- preprocessFile' prog path
-      let defs = filter (not . isImport) ast
-      pure $ map (nsDefinition currentModule) defs
-    processImport prog _ (SImport path name) = do
-      ast <- preprocessFile' prog path
-      let defs = filter (not . isImport) ast
-      pure $ map (nsDefinition name) defs
-    processImport _ _ _ = error "Unexpected non-import in processImport"
+makeRelativeTo :: FilePath -> FilePath -> FilePath
+makeRelativeTo f i =
+    let d = takeDirectory f
+    in normalise $ d </> i
 
 nsDefinitions :: String -> [TricuAST] -> [TricuAST]
 nsDefinitions moduleName = map (nsDefinition moduleName)
@@ -85,7 +103,7 @@ nsDefinition :: String -> TricuAST -> TricuAST
 nsDefinition "" def = def
 nsDefinition moduleName (SDef name args body)
   | isPrefixed name = SDef name args (nsBody moduleName body)
-  | otherwise = SDef (nsVariable moduleName name) 
+  | otherwise = SDef (nsVariable moduleName name)
                         args (nsBody moduleName body)
 nsDefinition moduleName other =
   nsBody moduleName other
@@ -106,7 +124,7 @@ nsBody moduleName (TStem subtree) =
   TStem (nsBody moduleName subtree)
 nsBody moduleName (SDef name args body)
   | isPrefixed name = SDef name args (nsBody moduleName body)
-  | otherwise = SDef (nsVariable moduleName name) 
+  | otherwise = SDef (nsVariable moduleName name)
                         args (nsBody moduleName body)
 nsBody _ other = other
 
@@ -116,13 +134,20 @@ nsBodyScoped moduleName args body = case body of
     if name `elem` args
       then SVar name
       else nsBody moduleName (SVar name)
-  SApp func arg -> SApp (nsBodyScoped moduleName args func) (nsBodyScoped moduleName args arg)
-  SLambda innerArgs innerBody -> SLambda innerArgs (nsBodyScoped moduleName (args ++ innerArgs) innerBody)
-  SList items -> SList (map (nsBodyScoped moduleName args) items)
-  TFork left right -> TFork (nsBodyScoped moduleName args left) (nsBodyScoped moduleName args right)
-  TStem subtree -> TStem (nsBodyScoped moduleName args subtree)
+  SApp func arg ->
+    SApp (nsBodyScoped moduleName args func) (nsBodyScoped moduleName args arg)
+  SLambda innerArgs innerBody ->
+    SLambda innerArgs (nsBodyScoped moduleName (args ++ innerArgs) innerBody)
+  SList items ->
+    SList (map (nsBodyScoped moduleName args) items)
+  TFork left right ->
+    TFork (nsBodyScoped moduleName args left)
+          (nsBodyScoped moduleName args right)
+  TStem subtree ->
+    TStem (nsBodyScoped moduleName args subtree)
   SDef name innerArgs innerBody ->
-    SDef (nsVariable moduleName name) innerArgs (nsBodyScoped moduleName (args ++ innerArgs) innerBody)
+    SDef (nsVariable moduleName name) innerArgs
+         (nsBodyScoped moduleName (args ++ innerArgs) innerBody)
   other -> other
 
 isPrefixed :: String -> Bool

src/Lexer.hs

@@ -59,7 +59,7 @@ keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
 identifier :: Lexer LToken
 identifier = do
   first <- lowerChar <|> char '_'
-  rest  <- many $ letterChar 
+  rest  <- many $ letterChar
               <|> digitChar <|> char '_' <|> char '-' <|> char '?'
               <|> char '$'  <|> char '#' <|> char '@' <|> char '%'
   let name = first : rest

src/Main.hs

@@ -8,7 +8,9 @@ import Research
 
 import Control.Monad          (foldM)
 import Control.Monad.IO.Class (liftIO)
+import Data.Version           (showVersion)
 import Text.Megaparsec        (runParser)
+import Paths_tricu            (version)
 import System.Console.CmdArgs
 
 import qualified Data.Map as Map
@@ -52,10 +54,12 @@ decodeMode = TDecode
 
 main :: IO ()
 main = do
+  let versionStr = "tricu Evaluator and REPL " ++ showVersion version
   args <- cmdArgs $ modes [replMode, evaluateMode, decodeMode]
     &= help "tricu: Exploring Tree Calculus"
     &= program "tricu"
-    &= summary "tricu Evaluator and REPL"
+    &= summary versionStr
+    &= versionArg [explicit, name "version", summary versionStr]
   case args of
     Repl -> do
       putStrLn "Welcome to the tricu REPL"

src/Parser.hs

@@ -255,9 +255,9 @@ parseSingleItemM = do
 
 parseVarM :: ParserM TricuAST
 parseVarM = do
-  token <- satisfyM (\case 
+  token <- satisfyM (\case
     LNamespace _ -> True
-    LIdentifier _ -> True 
+    LIdentifier _ -> True
     _ -> False)
   case token of
     LNamespace ns -> do

src/REPL.hs

@@ -8,59 +8,109 @@ import Research
 
 import Control.Exception         (SomeException, catch)
 import Control.Monad.IO.Class    (liftIO)
-import Control.Monad.Catch (handle, MonadCatch)
+import Control.Monad.Catch       (handle, MonadCatch)
+import Control.Monad.Trans.Class (lift)
+import Control.Monad.Trans.Maybe (MaybeT(..), runMaybeT)
 import Data.Char                 (isSpace)
-import Data.List                 (dropWhile, dropWhileEnd, intercalate)
+import Data.List                 ( dropWhile
+                                 , dropWhileEnd
+                                 , isPrefixOf)
 import System.Console.Haskeline
 
 import qualified Data.Map as Map
 
 repl :: Env -> IO ()
-repl env = runInputT defaultSettings (withInterrupt (loop env))
+repl env = runInputT settings (withInterrupt (loop env True))
   where
-    loop :: Env -> InputT IO ()
-    loop env = handle (interruptHandler env) $ do
+    settings :: Settings IO
+    settings = Settings
+      { complete = completeWord Nothing " \t" completeCommands
+      , historyFile = Just ".tricu_history"
+      , autoAddHistory = True
+      }
+
+    completeCommands :: String -> IO [Completion]
+    completeCommands str = return $ map simpleCompletion $
+      filter (str `isPrefixOf`) commands
+      where
+        commands = ["!exit", "!decode", "!definitions", "!import"]
+
+    loop :: Env -> Bool -> InputT IO ()
+    loop env decode = handle (interruptHandler env decode) $ do
       minput <- getInputLine "tricu < "
       case minput of
         Nothing -> outputStrLn "Exiting tricu"
         Just s
+          | strip s == "" -> loop env decode
           | strip s == "!exit" -> outputStrLn "Exiting tricu"
-          | strip s == "" -> loop env
-          | strip s == "!import" -> do
-              path <- getInputLine "File path to load < "
-              case path of
-                Nothing -> do
-                  outputStrLn "No input received; stopping import."
-                  loop env
-                Just p -> do
-                  loadedEnv <- liftIO $ evaluateFileWithContext env 
-                    (strip p) `catch` \e -> errorHandler env e
-                  loop $ Map.delete "!result" (Map.union loadedEnv env)
-          | take 2 s == "--" -> loop env
+          | strip s == "!decode" -> do
+              outputStrLn $ "Decoding " ++ (if decode then "disabled" else "enabled")
+              loop env (not decode)
+          | strip s == "!definitions" -> do
+              let defs = Map.keys $ Map.delete "!result" env
+              if null defs
+                then outputStrLn "No definitions discovered."
+                else do
+                  outputStrLn "Available definitions:"
+                  mapM_ outputStrLn defs
+              loop env decode
+          | "!import" `isPrefixOf` strip s -> handleImport env decode
+          | take 2 s == "--" -> loop env decode
           | otherwise -> do
-              newEnv <- liftIO $ processInput env s `catch` errorHandler env
-              loop newEnv
+              newEnv <- liftIO $ processInput env s decode `catch` errorHandler env
+              loop newEnv decode
 
-    interruptHandler :: Env -> Interrupt -> InputT IO ()
-    interruptHandler env _ = do
+    handleImport :: Env -> Bool -> InputT IO ()
+    handleImport env decode = do
+      result <- runMaybeT $ do
+        let fileSettings = setComplete completeFilename defaultSettings
+        path <- MaybeT $ runInputT fileSettings $
+          getInputLineWithInitial "File path to load < " ("", "")
+
+        contents <- liftIO $ readFile (strip path)
+
+        if | Left err <- parseProgram (lexTricu contents) -> do
+               lift $ outputStrLn $ "Parse error: " ++ handleParseError err
+               MaybeT $ return Nothing
+           | Right ast <- parseProgram (lexTricu contents) -> do
+               ns <- MaybeT $ runInputT defaultSettings $
+                 getInputLineWithInitial "Namespace (or !Local for no namespace) < " ("", "")
+
+               processedAst <- liftIO $ preprocessFile (strip path)
+               let namespacedAst | strip ns == "!Local" = processedAst
+                                | otherwise = nsDefinitions (strip ns) processedAst
+                   loadedEnv = evalTricu env namespacedAst
+               return loadedEnv
+
+      if | Nothing <- result -> do
+             outputStrLn "Import cancelled."
+             loop env decode
+         | Just loadedEnv <- result ->
+             loop (Map.delete "!result" loadedEnv) decode
+
+    interruptHandler :: Env -> Bool -> Interrupt -> InputT IO ()
+    interruptHandler env decode _ = do
       outputStrLn "Interrupted with CTRL+C\n\
                   \You can use the !exit command or CTRL+D to exit"
-      loop env
+      loop env decode
 
-    processInput :: Env -> String -> IO Env
-    processInput env input = do
+    processInput :: Env -> String -> Bool -> IO Env
+    processInput env input decode = do
       let asts   = parseTricu input
           newEnv = evalTricu env asts
-      if
-        | Just r <- Map.lookup "!result" newEnv -> do
-          putStrLn $ "tricu > " ++ decodeResult r
-        | otherwise -> return ()
+      case Map.lookup "!result" newEnv of
+        Just r -> do
+          putStrLn $ "tricu > " ++
+            if decode
+              then decodeResult r
+              else show r
+        Nothing -> pure ()
       return newEnv
-    
+
     errorHandler :: Env -> SomeException -> IO (Env)
     errorHandler env e = do
       putStrLn $ "Error: " ++ show e
       return env
-    
+
     strip :: String -> String
     strip = dropWhileEnd isSpace . dropWhile isSpace

src/Research.hs

@@ -53,7 +53,7 @@ data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii | Decode
   deriving (Show, Data, Typeable)
 
 -- Environment containing previously evaluated TC terms
-type Env = Map.Map String T 
+type Env = Map.Map String T
 
 -- Tree Calculus Reduction
 apply :: T -> T -> T
@@ -122,7 +122,7 @@ formatResult Ascii        = toAscii
 formatResult Decode       = decodeResult
 
 toSimpleT :: String -> String
-toSimpleT s = T.unpack 
+toSimpleT s = T.unpack
   $ replace "Fork" "t"
   $ replace "Stem" "t"
   $ replace "Leaf" "t"

test/Spec.hs

@@ -30,7 +30,7 @@ tests = testGroup "Tricu Tests"
   , parser
   , simpleEvaluation
   , lambdas
-  , baseLibrary
+  , providedLibraries
   , fileEval
   , modules
   , demos
@@ -341,139 +341,107 @@ lambdas = testGroup "Lambda Evaluation Tests"
    , testCase "Lambda with a list literal" $ do
         let input = "f = (\\x : x)\nf [t (t t)]"
         runTricu input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+
+  , testCase "Lambda with list literal" $ do
+      let input = "(\\a : [(a)]) 1"
+      runTricu input @?= "Fork (Fork (Stem Leaf) Leaf) Leaf"
   ]
 
-baseLibrary :: TestTree
-baseLibrary = testGroup "Library Tests"
-  [ testCase "K combinator 1" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "k (t) (t t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Leaf
-
-  , testCase "K combinator 2" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "k (t t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Stem Leaf
-
-  , testCase "K combinator 3" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "k (t t t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork Leaf Leaf
-
-  , testCase "S combinator" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "s (t) (t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork Leaf (Stem Leaf)
-
-  , testCase "SKK == I (fully expanded)" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "s k k"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork (Stem (Stem Leaf)) (Stem Leaf)
-
-  , testCase "I combinator" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "i not?"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) (Fork Leaf (Fork Leaf Leaf))
-
-  , testCase "Triage test Leaf" $ do
-      library <- evaluateFile "./lib/base.tri"
+providedLibraries :: TestTree
+providedLibraries = testGroup "Library Tests"
+  [ testCase "Triage test Leaf" $ do
+      library <- evaluateFile "./lib/list.tri"
       let input = "test t"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Leaf\""
 
   , testCase "Triage test (Stem Leaf)" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "test (t t)"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Stem\""
 
   , testCase "Triage test (Fork Leaf Leaf)" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "test (t t t)"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Fork\""
 
   , testCase "Boolean NOT: true" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? true"
           env = result $ evalTricu library (parseTricu input)
       env @?= Leaf
 
   , testCase "Boolean NOT: false" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? false"
           env = result $ evalTricu library (parseTricu input)
       env @?= Stem Leaf
 
 
   , testCase "Boolean AND TF" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t t) (t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND FT" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t) (t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND FF" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t) (t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND TT" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t t) (t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "List head" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "head [(t) (t t) (t t t)]"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "List tail" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "head (tail (tail [(t) (t t) (t t t)]))"
           env = evalTricu library (parseTricu input)
       result env @?= Fork Leaf Leaf
 
   , testCase "List map" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "head (tail (map (\\a : (t t t)) [(t) (t) (t)]))"
           env = evalTricu library (parseTricu input)
       result env @?= Fork Leaf Leaf
 
   , testCase "Empty list check" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "emptyList? []"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "Non-empty list check" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? (emptyList? [(1) (2) (3)])"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "Concatenate strings" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "lconcat \"Hello, \" \"world!\""
+      library <- evaluateFile "./lib/list.tri"
+      let input = "append \"Hello, \" \"world!\""
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Hello, world!\""
 
   , testCase "Verifying Equality" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "equal? (t t t) (t t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
@@ -490,12 +458,12 @@ fileEval = testGroup "File evaluation tests"
       res @?= Fork (Stem Leaf) Leaf
 
   , testCase "Mapping and Equality" $ do
-      library <- liftIO $ evaluateFile "./lib/base.tri"
+      library <- liftIO $ evaluateFile "./lib/list.tri"
       fEnv    <- liftIO $ evaluateFileWithContext library "./test/map.tri"
       (mainResult fEnv) @?= Stem Leaf
 
   , testCase "Eval and decoding string" $ do
-      library <- liftIO $ evaluateFile "./lib/base.tri"
+      library <- liftIO $ evaluateFile "./lib/list.tri"
       res <- liftIO $ evaluateFileWithContext library "./test/string.tri"
       decodeResult (result res) @?= "\"String test!\""
   ]

test/cycle-1.tri

@@ -1,4 +1,4 @@
 
-!import "test/cycle-2.tri" Cycle2
+!import "cycle-2.tri" Cycle2
 
 cycle1 = t Cycle2.cycle2

test/cycle-2.tri

@@ -1,4 +1,4 @@
 
-!import "test/cycle-1.tri" Cycle1
+!import "cycle-1.tri" Cycle1
 
 cycle2 = t Cycle1.cycle1

test/local-ns/1.tri

@@ -1,4 +1,4 @@
 
-!import "test/local-ns/2.tri" Two
+!import "2.tri" Two
 
 main = Two.x

test/local-ns/2.tri

@@ -1,2 +1,2 @@
 
-!import "test/local-ns/3.tri" !Local
+!import "3.tri" !Local

test/local-ns/3.tri

@@ -1,2 +1 @@
-
 x = 3

test/map.tri

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

test/multi-level-A.tri

@@ -1,2 +1,2 @@
-!import "./test/multi-level-B.tri" B
+!import "multi-level-B.tri" B
 main = B.main

test/multi-level-B.tri

@@ -1,2 +1,2 @@
-!import "./test/multi-level-C.tri" C
+!import "multi-level-C.tri" C
 main = C.val

test/namespace-A.tri

@@ -1,2 +1,2 @@
-!import "./test/namespace-B.tri" B
+!import "namespace-B.tri" B
 main = B.x

test/string.tri

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

test/vars-A.tri

@@ -1,6 +1,6 @@
 
-!import "./test/vars-B.tri" B
+!import "vars-B.tri" B
 
-!import "./test/vars-C.tri" C
+!import "vars-C.tri" C
 
 main = B.y (C.z)

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.13.0
+version:        0.16.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
@@ -27,10 +27,12 @@ executable tricu
     , cmdargs
     , containers
     , exceptions
+    , filepath
     , haskeline
     , megaparsec
     , mtl
     , text
+    , transformers
   other-modules:
     Eval
     FileEval
@@ -54,6 +56,7 @@ test-suite tricu-tests
     , cmdargs
     , containers
     , exceptions
+    , filepath
     , haskeline
     , megaparsec
     , mtl
@@ -61,6 +64,7 @@ test-suite tricu-tests
     , tasty-hunit
     , tasty-quickcheck
     , text
+    , transformers
   default-language:    Haskell2010
   other-modules:
     Eval