exprparse/test.icl

   1 module test
   2
   3 import StdEnv
   4
   5 import Data.Functor
   6 import Control.Applicative
   7
   8 import Text.Parsers.Simple.Core
   9 import Text.Parsers.Simple.Chars
  10
  11 preprocess :: [Char] -> [Char]
  12 preprocess c = ['((((':foldr prep ['))))'] c]
  13 where
  14         prep '(' cs = ['(','(','(','(':cs]
  15         prep ')' cs = [')',')',')',')':cs]
  16         prep '^' cs = [')','^','(':cs]
  17         prep '*' cs = [')',')','*','(','(':cs]
  18         prep '/' cs = [')',')','/','(','(':cs]
  19         prep '+' cs = [')',')',')','+','(','(','(':cs]
  20         prep '-' cs = [')',')',')','-','(','(','(':cs]
  21         prep c cs   = [c:cs]
  22
  23 :: Expr = BinOp Expr Char Expr | Lit Int | Var [Char]
  24
  25 parseExpr :: Parser Char Expr
  26 parseExpr
  27         =   BinOp <$ pToken '(' <*> parseExpr <*> pOneOf ['^*/+-'] <*> parseExpr <* pToken ')'
  28         <|> Var <$> some pAlpha
  29         <|> Lit o toInt o toString <$> some pDigit
  30
  31 Start = parse parseExpr (preprocess ['a'])
  32 //Start = parse parseExpr (preprocess ['a*b+c^d/e'])