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MiyamonY/rpn.hs

Created February 27, 2015 13:01
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rpn.hs
solveRPN :: String -> Double
solveRPN = head . foldl foldingFunction [] . words
where foldingFunction (x:y:ys) "*" = (y * x) : ys
foldingFunction (x:y:ys) "+" = (y + x) : ys
foldingFunction (x:y:ys) "-" = (y - x) : ys
foldingFunction (x:y:ys) "/" = (y / x) : ys
foldingFunction (x:y:ys) "^" = (y ** x) : ys
foldingFunction (x:xs) "ln" = log x : xs
foldingFunction xs "sum" = [sum xs]
foldingFunction xs numberString = read numberString : xs
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