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oropon/RPN Calculator

Created January 14, 2014 13:13
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RPN Calculator
module Main where
main = print $ calc cs
cs = "3 4 + 5 2 - * 4 2 / +"
calc :: String -> Float
calc = calc' [] . words
calc' :: [Float] -> [String] -> Float
calc' [x] [] = x
calc' (x':x:xs) (y:ys)
| y == "+" = calc' (x + x' : xs) ys
| y == "-" = calc' (x - x' : xs) ys
| y == "*" = calc' (x * x' : xs) ys
| y == "/" = calc' (x / x' : xs) ys
calc' stk (y:ys) = calc' (read y : stk) ys
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