On Wed, Dec 21, 2005 at 10:25:09AM -0800, Randal L. Schwartz wrote: > >>>>> "Uri" == Uri Guttman <[EMAIL PROTECTED]> writes: > > Uri> i will let damian handle this one (if he sees it). but an idea would be > Uri> to allow some form ofkey extraction via a closure with lazy evaluation > Uri> of the secondary (and slower) key. > > I still don't see that. I understand about the lazy key evaluation. > However, the sort block in Perl5 contains more than just two key > computations: it also contains the logic to decide *how* to compare > the keys, and *when* more information is needed (a secondary key step, > for example). Not sure how you're going to replace that with just > information about how to compute "a key". I think you've had your head > inside GRT for too long. :) > > So, for the simple case (string sort against some function of each item), > I can see the need for a good shortcut. However, the general case (let > me tell you how to sort two items), you'll still need a very perl5-ish > interface.
If I understand the p6 way correctly (which is not necessarily true :-) it provides the key computation function in addition to the comparison function. So, the key computation can return a list of keys for each value (possibly in lazy not-yet-evaluated for so that the computation is only incurred the first time that that key component is actually used). The comparison function is often simpler than a p5 comparison function (because of the existance of the key function and because of the smarter match capabilities) but could still be as complicated a a p5 sort comparison function for those rare cases that really need it. --
