On Thu, Feb 24, 2005 at 05:17:50PM +0000, Nicholas Clark wrote: : 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.
I belive that mechanism doesn't actually combine with parameter MMD to pick the original routine to call based on context. If I recall, it only comes into play at the time you actually try to return. Larry
