Daniel Fischer
However, since you're asking about cost, which indicates that you care for performance, the above would be better written as
[x*x*x | x <- list]
unless you depend on the small differences in the outcome [I'm not quite sure how many bits may be affected, not many, typically none or one]. Functions like (**), exp, log, sin, cos, ... are slow, very slow. If the exponent is a small (positive) integer, specifically giving a sequence of multiplication steps is much faster, also using (^) instead of (**) is faster for small exponents (but slower than an explicit multiplication sequence).
Neither does this really match my intuition, nor can I confirm it with an experiment. Applying (** 3) a million times to a Double takes a second and gives me the expected Infinity. Applying (^3) or (\x -> x*x*x) a million times to the same value, well, I didn't want to wait for it to finish. The experiment was ran with the following codes in GHCi: iterate (** 3) 1.000000001 !! 1000000 iterate (^3) 1.000000001 !! 1000000 iterate (\x -> x*x*x) 1.000000001 !! 1000000 Note that exponentiation is a cheap operation on Double. Greets Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/