Re: [pro] why :key arguments?

On Mon, Jul 4, 2011 at 11:31 AM, Tamas Papp tkpapp@gmail.com wrote:

Why do some CL library functions have :key arguments?

[...]

but it is a bit cumbersome.  I can make my code simpler by relying on calls like

(quantiles (map 'vector key vector) quantiles)

This not only conses "a bit more", it also duplicates traversal efforts - The original list must be traversed, and the consed-up list of key values as well. I think it is prudent that the CL library functions offer ways to reduce consing for cases where "a bit" is too much (and "a bit" can become a lot if a program operates on long lists).

-Hans