Add parenthesis to parsing

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

diff --git a/AST.hs b/AST.hs
index 424cfbe7b13010e0960e4b88a1675cdcfa3b3f0f..73523d6d4c8a37cef977d5614d355aaac13756af 100644 (file)
--- a/AST.hs
+++ b/AST.hs
@@ -1,26 +1,87 @@
 module AST where
 
+import Data.Char
 import Text.Read
 import Text.ParserCombinators.ReadP hiding ((+++), choice)
 
-data BinOpType = Add | Sub | Mul
+newtype Program = Program [AST]
+  deriving Show
+
+instance Read Program where
+  readPrec = fmap Program $ lift $ sepBy1 (readS_to_P reads) $ do
+    skipSpaces
+    char ';'
+    skipSpaces
+
+data AST = Function String [String] Expr
+         | Eval Expr
   deriving Show
 data Expr = Num Float
           | BinOp BinOpType Expr Expr
+          | Var String
+          | Call String [Expr]
+          | If Expr 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
+            name <- munch1 isAlpha
+            params <- between (char '(') (char ')') $
+                      sepBy (munch1 isAlpha) skipSpaces
+            skipSpaces
+            body <- readS_to_P reads
+            return (Function name params body)
 
 instance Read Expr where
-  readPrec = choice [ parseNum
-                    , parseBinOp '+' Add
-                    , parseBinOp '-' Sub
-                    , parseBinOp '*' Mul
+  readPrec = choice [ parseParens
+                    , parseNum
+                    , parseVar
+                    , parseCall
+                    , parseIf
+                    , parseBinOp "+" Add
+                    , parseBinOp "-" Sub
+                    , parseBinOp "*" Mul
+                    , parseBinOp ">" (Cmp GT)
+                    , parseBinOp "<" (Cmp LT)
+                    , parseBinOp "==" (Cmp EQ)
                     ]
-    where parseNum = Num <$> readPrec
-          parseBinOp c typ = step $ do
+    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)
+            params <- lift $ between (char '(') (char ')') $
+                        sepBy (readS_to_P reads)
+                              (skipSpaces >> char ',' >> skipSpaces)
+            return (Call func params)
+          parseBinOp s typ = step $ do
             a <- prec 11 readPrec
             lift $ do
               skipSpaces
-              char c
+              string s
               skipSpaces
             b <- readPrec
             return (BinOp typ a b)
+          parseIf = do
+            lift $ do
+              string "if"
+              skipSpaces
+            cond <- step readPrec
+            lift $ do
+              skipSpaces
+              string "then"
+              skipSpaces
+            thenE <- step readPrec
+            lift $ do
+              skipSpaces
+              string "else"
+              skipSpaces
+            elseE <- step readPrec
+            return (If cond thenE elseE)