Parse defs and externs

[kaleidoscope-hs.git] / AST.hs

diff --git a/AST.hs b/AST.hs
index c766afc1570140a77690e9f19259a68def0ac967..7dad3a19e91eab9f12657101bd224b5c81742d07 100644 (file)
--- a/AST.hs
+++ b/AST.hs
@@ -1,5 +1,6 @@
 module AST where
 
+import Data.Char
 import Text.Read 
 import Text.ParserCombinators.ReadP hiding ((+++), choice)
 
@@ -21,9 +22,6 @@ instance Read Expr where
                     ]
     where parseNum = Num <$> readPrec
           parseVar = Var <$> lift (munch1 isAlpha)
-          -- use 'prec 1' and 'step' so that parsing 'a'
-          -- can only go one step deep, to prevent ininfite
-          -- recursion
           parseBinOp s prc op = prec prc $ do
             a <- step readPrec
             lift $ do
@@ -33,3 +31,27 @@ instance Read Expr where
             b <- readPrec
             return (BinOp op a b)
             
+data Prototype = Prototype String [String]
+  deriving Show
+
+instance Read Prototype where
+  readPrec = lift $ do
+    name <- munch1 isAlpha
+    params <- between (char '(') (char ')') $
+                sepBy (munch1 isAlpha) skipSpaces
+    return (Prototype name params)
+
+data AST = Function Prototype Expr
+         | Extern Prototype
+         | TopLevelExpr Expr
+  deriving Show
+
+instance Read AST where
+  readPrec = parseFunction +++ parseExtern +++ parseTopLevel
+    where parseFunction = do
+            lift $ string "def" >> skipSpaces
+            Function <$> readPrec <*> readPrec
+          parseExtern = do
+            lift $ string "extern" >> skipSpaces
+            Extern <$> readPrec
+          parseTopLevel = TopLevelExpr <$> readPrec