"Costello, Roger L."
This book [1] has a neat, simple example of making code more efficient.
[...]
Thus, by a little rework the number of multiplications is reduced from three to two. That is a significant efficiency improvement.
Cool, aye?
As Matthias noted correctly this is a well known method for exponentiation with arbitrary integer exponents (works even for rational exponents in certain groups). I would like to add that exactly this method drives the (^) exponentiation function, so your function becomes quad :: Num a => a -> a quad = (^4) and benefits from the same exponential speedup, although writing the direct multiplication may give you a performance improvement by a constant factor, which may or may not be significant. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/