Hello, Both my Hugs and my GHCi report a type error when presented with this. A possible repaired version looks like this: calc :: String -> Float calc = g . foldl f [] . words where f (x:y:zs) "+" = y+x:zs f (x:y:zs) "-" = y-x:zs f (x:y:zs) "*" = y*x:zs f (x:y:zs) "/" = y/x:zs f xs y = read y : xs g [r] = r Not as small, but still quite nice. Regards Thorkil On Tuesday 30 May 2006 15:10, Sebastian Sylvan wrote:
A bit OT perhaps, but I'd just like to point out this wonderful little code snippet from the Haskell wiki-page that I've always liked, in case nobody's seen it:
calc :: String -> Float calc = foldl f [] . words where f (x:y:zs) "+" = y+x:zs f (x:y:zs) "-" = y-x:zs f (x:y:zs) "*" = y*x:zs f (x:y:zs) "/" = y/x:zs f xs y = read y : xs
That's it. An RPN evaluator in a couple of lines.