Add for loops

[kaleidoscope-hs-old.git] / AST.hs

diff --git a/AST.hs b/AST.hs
index 720413652e4343740ad6268e0a866b0576e4c4aa..e5ea72ad3e059e33b71cb387b82a100b4c207a3a 100644 (file)
--- a/AST.hs
+++ b/AST.hs
@@ -2,47 +2,58 @@ module AST where
 
 import Data.Char
 import Text.Read
-import Text.ParserCombinators.ReadP hiding ((+++), choice)
+import Text.ParserCombinators.ReadP hiding ((+++), (<++), choice)
 
 newtype Program = Program [AST]
   deriving Show
 
 instance Read Program where
-  readPrec = fmap Program $ lift $ sepBy1 (readS_to_P reads) $ do
+  readPrec = fmap Program $ lift $ do
+    asts <- sepBy1 (readS_to_P reads) $ do
       skipSpaces
       char ';'
       skipSpaces
+    optional $ char ';'
+    skipSpaces
+    return asts
 
 data AST = Function String [String] Expr
+         | Extern String [String]
          | Eval Expr
   deriving Show
-data Expr = Num Float
+data Expr = Num Double
           | BinOp BinOpType Expr Expr
           | Var String
           | Call String [Expr]
           | If Expr Expr Expr
+          | For String Expr Expr (Maybe Expr) Expr
   deriving Show
 data BinOpType = Add | Sub | Mul | Cmp Ordering
   deriving Show
 
 instance Read AST where
-  readPrec = parseFunction +++ (Eval <$> readPrec)
-    where parseFunction = lift $ do
-            skipSpaces
-            string "def"
-            skipSpaces
+  readPrec = parseFunction +++ parseExtern +++ (Eval <$> readPrec)
+    where parseFunction = do
+            lift $ string "def" >> skipSpaces
+            (name, params) <- parsePrototype
+            lift skipSpaces
+            Function name params <$> readPrec
+          parseExtern = do
+            lift $ string "extern" >> skipSpaces
+            uncurry Extern <$> parsePrototype
+          parsePrototype = lift $ do
             name <- munch1 isAlpha
             params <- between (char '(') (char ')') $
                       sepBy (munch1 isAlpha) skipSpaces
-            skipSpaces
-            body <- readS_to_P reads
-            return (Function name params body)
+            return (name, params)
 
 instance Read Expr where
-  readPrec = choice [ parseNum
+  readPrec = choice [ parseParens
+                    , parseNum
                     , parseVar
                     , parseCall
                     , parseIf
+                    , parseFor
                     , parseBinOp "+" Add
                     , parseBinOp "-" Sub
                     , parseBinOp "*" Mul
@@ -50,7 +61,9 @@ instance Read Expr where
                     , parseBinOp "<" (Cmp LT)
                     , parseBinOp "==" (Cmp EQ)
                     ]
-    where parseNum = Num <$> readPrec
+    where parseParens = step $ lift $
+            between (char '(') (char ')') (readS_to_P reads)
+          parseNum = Num <$> readPrec
           parseVar = Var <$> lift (munch1 isAlpha)
           parseCall = do
             func <- lift (munch1 isAlpha)
@@ -59,13 +72,12 @@ instance Read Expr where
                               (skipSpaces >> char ',' >> skipSpaces)
             return (Call func params)
           parseBinOp s typ = step $ do
-            a <- prec 11 readPrec
+            a <- prec 11 readPrec -- set recursion limit of 11
             lift $ do
               skipSpaces
               string s
               skipSpaces
-            b <- readPrec
-            return (BinOp typ a b)
+            BinOp typ a <$> readPrec
           parseIf = do
             lift $ do
               string "if"
@@ -82,3 +94,18 @@ instance Read Expr where
               skipSpaces
             elseE <- step readPrec
             return (If cond thenE elseE)
+          parseFor = do
+            lift $ do
+              string "for"
+              skipSpaces
+            identifier <- lift (munch1 isAlpha)
+            lift $ skipSpaces >> char '=' >> skipSpaces
+            start <- step readPrec
+            lift $ skipSpaces >> char ',' >> skipSpaces
+            cond <- step readPrec
+            step' <- (do
+              lift $ skipSpaces >> char ',' >> skipSpaces
+              Just <$> step readPrec) <++ pure Nothing
+            lift $ skipSpaces >> string "in" >> skipSpaces
+            body <- step readPrec
+            return (For identifier start cond step' body)