Re: [Haskell-cafe] Re: Solving a geometry problem with Haskell

On Sat, 12 Jan 2008, Achim Schneider wrote:

"Rafael Almeida" wrote:

...

perfectSquares :: [Integer] perfectSquares = zipWith (*) [1..] [1..]

...

isPerfectSquare :: Integer -> Bool isPerfectSquare x = (head $ dropWhile (

what about

module Main where

isPerfectSquare :: Integer -> Bool isPerfectSquare n = sqrrt == fromIntegral (truncate sqrrt) where sqrrt = sqrt $ fromIntegral n

? It's a hell alot faster, but I have no idea if some numerical property of square roots could make it give different results than your version, in rare cases.

The rare cases occur for big numbers. http://www.haskell.org/haskellwiki/Generic_number_type#isSquare