Andrew J Bromage wrote:

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