data Expr = Num Float
| Var String
| BinOp BinOp Expr Expr
+ | Call String [Expr]
deriving Show
data BinOp = Add | Sub | Mul | Cmp Ordering
deriving Show
instance Read Expr where
- readPrec = choice [ parseNum
+ readPrec = parens $ choice [ parseNum
, parseVar
+ , parseCall
, parseBinOp "<" 10 (Cmp LT)
, parseBinOp "+" 20 Add
, parseBinOp "-" 20 Sub
skipSpaces
b <- readPrec
return (BinOp op a b)
+ parseCall = do
+ func <- lift (munch1 isAlpha)
+ params <- lift $ between (char '(') (char ')') $
+ sepBy (readS_to_P reads)
+ (skipSpaces >> char ',' >> skipSpaces)
+ return (Call func params)
data Prototype = Prototype String [String]
deriving Show