X-Git-Url: https://git.lukelau.me/?p=kaleidoscope-hs-old.git;a=blobdiff_plain;f=AST.hs;h=99b6d42a23b9af254c8767ac969accc8248f03bb;hp=720413652e4343740ad6268e0a866b0576e4c4aa;hb=749e5a29af22fc74b8c597485de9be6485ccc62f;hpb=fff481b022d2d5ed24ce3faf686ca783e7860741

diff --git a/AST.hs b/AST.hs
index 7204136..99b6d42 100644
--- a/AST.hs
+++ b/AST.hs
@@ -8,15 +8,20 @@ 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]
@@ -26,20 +31,24 @@ 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
@@ -50,7 +59,9 @@ 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 +70,12 @@ 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"