On Fri, Feb 25, 2005 at 12:45:45AM +0800, Autrijus Tang wrote: > On Wed, Feb 23, 2005 at 12:17:19PM -0800, Larry Wall wrote: > > : And how does all this combine with the notion of context? > > > > Lazily, for the most part. In some cases we can determine context at > > compile time, but often not. Certainly a subroutine cannot determine > > what context it was called in until it's actually called, unless we > > venture into return-value MMD, which has problems resolving against > > parameter MMD.
> However, retval-based MMD is neccessary to ensure compile-time > dispatch, and plays really well with type inferencing in general. > So another solution is to mark ambiguate retval-based dispatches as > ill-typed, and let the programmer resolve it by explicit type > annotation. But making it default is probably too much B&D. Not that the tail should wag the dog, but as I remember it, parrot can do return-value MMD "for free", because the continuation-passing style of function calling means that actually there's no difference between a function call and a function return. [It's all just one maze of non-local gotos :-)] So if I understand it correctly, there's no speed hit in doing return- value MMD. Just a sanity hit. Nicholas Clark
