gistfile1.txt

module Expressions where

import Text.ParserCombinators.Parsec
import Control.Monad
import Control.Monad.Error
import System.IO

data Term a = IntVal Integer
            | StrVal String
            | RealVal Double

data Expr a =  BinOp String (Expr a) (Expr a)
            |  UnOp String (Expr a)
            |  Fun  String (Expr a)
            |  Ident String 
            |  IfElse (Expr a) (Expr a) (Expr a)
            |  Cond   (Expr a) [Expr a]
            |  Term a
            deriving (Show, Eq)

evaluate :: (Eq a) => Expr a -> b
evaluate (BinOp "+" e1 e2) = (evaluate e1) + (evaluate e2)
evaluate (Term (IntVal i)) = i
evaluate (Term (StrVal s)) = s
evaluate (Term (RealVal r)) = r
evaluate _ = undefined


------
Expressions.hs:24:30:
    Couldn't match type `Integer' with `[Char]'
    Expected type: b
      Actual type: String
    In the expression: s
    In an equation for `evaluate': evaluate (Term (StrVal s)) = s

Expressions.hs:25:31:
    Couldn't match type `Integer' with `Double'
    Expected type: b
      Actual type: Double
    In the expression: r
    In an equation for `evaluate': evaluate (Term (RealVal r)) = r
Failed, modules loaded: none.