Raphael Descamps wrote: > I personally don't understand why we don't have a exclude and alias > operator in Perl 6 but I have not read all the synopses and don't have > an overview.
I don't think that it's explicitly spelled out anywhere; but the reason is fairly straightforward: exclude and alias would break the interface. Take Stringy as an example: when a class says "does Stringy", it's making certain promises about its syntax and semantics: e.g., it will have a "method say", and "method say" should result in sending a string of text to an output stream. Thus, any routine that asks for "Stringy $x" as one of its parameters should be able to put "$x.say" in its code and get the expected results. But if Foo does Stringy but excludes or aliases .say, a routine that asks for a Stringy $x but receives a Foo $x will run into problems the moment "$x.say" shows up in its code. If .say was excluded, the semantics are no longer available at all. If it was aliased, the semantics are still available under another name; but that does the routine no good, because it has no idea what the new name is, or even that it exists. Either way, "$x.say" will not do what the routine intended it to do. The interface is broken. -- Jonathan "Dataweaver" Lang
