Am Montag, den 19.10.2009, 16:43 -0700 schrieb Jon Lang: > 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.
You're of course right! It's clearly explained in Apocalypse 12 (Conflict Resolution): "A role without implementation degenerates to an interface". I don't know why but I didn't realised before that not implementing exclude and alias was in fact an important design decision: I have probably read to much traits papers and not enough Apocalyses ;) On one side you lose flexibility to resolve some composition conflicts but the fact that a role also define a contract is of course a big win, particulary for a language like perl 6 supporting optional statical typing. The traits paper only focus on dynamic typing. It also explain why perl 6 as a so strong support for delegation, as it is the proposed way to solve composition conflicts. It's time to read Apacalyse 12 again as I am now able to anderstand it :)
