Author: larry Date: Tue May 29 17:38:24 2007 New Revision: 14408 Modified: doc/trunk/design/syn/S06.pod
Log: Extensibility of "is cached" explained, as requested by gabriele renzi++ Modified: doc/trunk/design/syn/S06.pod ============================================================================== --- doc/trunk/design/syn/S06.pod (original) +++ doc/trunk/design/syn/S06.pod Tue May 29 17:38:24 2007 @@ -13,9 +13,9 @@ Maintainer: Larry Wall <[EMAIL PROTECTED]> Date: 21 Mar 2003 - Last Modified: 21 May 2007 + Last Modified: 29 May 2007 Number: 6 - Version: 84 + Version: 85 This document summarizes Apocalypse 6, which covers subroutines and the @@ -1472,12 +1472,32 @@ =item C<is cached> -Marks a subroutine as being memoized. +Marks a subroutine as being memoized, or at least memoizable. The +compiler is free to choose any kind of caching algorithm (including +non-expiring, random, lru, pseudo-lru, or adaptive algoritms, or +even no caching algorithm at all). The run-time system is free to +choose any kind of maximum cache size depending on the availability +of memory and trends in usage patterns. You may suggest a particular +cache size by passing a numeric argument, and some of the possible +algorithms may pay attention to it. You may also pass C<*> for the +size to request a non-expiring cache (complete memoization). The +compiler is free to ignore this too. + +The intent of this pragma is to specify performance hints without +mandating any exact behavior. Use of this pragma should not change +semantics of the program, and this pragma will not be extended to +reinvent other existing ways of achieving the same effect. To gain +more control, write your own trait handler to allow the use of a more +specific trait, such as "C<is lru(42)>". Alternately, just +use a state hash keyed on the sub's argument capture to write +your own memoization with complete control from within the subroutine +itself. =item C<is inline> I<Suggests> to the compiler that the subroutine is a candidate for -optimization via inlining. +optimization via inlining. Basically promises that nobody is going +to try to wrap this subroutine (or that if they do, you don't care). =item C<is tighter>/C<is looser>/C<is equiv>
