3 Mar
2003
3 Mar
'03
11:57 p.m.
Andrew J Bromage
G'day.
On Mon, Mar 03, 2003 at 11:49:29AM +0200, Cagdas Ozgenc wrote:
Yes, I thought about these too. Do you find these functions practically useful? Can you give an example where I can utilize these functions?
Functions like this are useful for plugging into higher-order functions to tailor them for your specific needs.
Here's an artificial example:
length = sum . map (const 1)
Incidentally, here's another artificial example:
indices = zipWith const [0..]
This can be used to define scanl, incidentally:
scanl f z xn = [foldl f z (take i xn) | i <- indices (undefined:xn)]
(where the undefined: just reflects the fact that we want one more element than xn has). Jon Cast