On 27 September 2010 12:51, Johan Brichau <[email protected]> wrote: > > On 27 Sep 2010, at 11:28, Igor Stasenko wrote: > >> On 27 September 2010 11:54, Johan Brichau <[email protected]> wrote: >>> >>> On 27 Sep 2010, at 10:38, Lukas Renggli wrote: >>> >>>>> Am I wrong? >>>> >>>> Yes, almost always one should probably use #= instead of #==. >>> >>> I will add that to the exercise :-) >>> The exercise actually makes students aware of the difference between >>> strings and symbols (which should be pointer-equal) >>> >> >> I think you can avoid using 'equal' word when describing a #== comparison. >> It can be explained as 'test whether comparands are same object or not' >> while #= is test whether two objects equal or not. > > Yes, this is exactly what the exercise is doing. > I want them to be aware that equal _symbols_ are the same objects, but that > equal _strings_ are not, which is why I let them evaluate: > > a := #foobar. > b := #foobar. > a == b. > > a := 'foobar'. > b := 'foobar'. > a == b > > The problem is that evaluating the second snippet also yields true in > Pharo/Squeak, so I cannot illustrate it using these snippets (which works > fine in Visualworks, btw). > > Yes, this is a compiler optimization and, yes, people should use #= instead > of #== normally. But imho the optimization yields a wrong semantics, which is > why I posted the email. > > I have absolutely no clue if it can be changed (I am not familiar with the > compiler implementation *at all*), but I would be happy to look over the > shoulder of an experienced compiler hacker during the next sprint to learn ;-) > Why waiting for sprint?
Implement String>>literalEqueal: anObject ^ self == anObject and then you have 'aaa' == 'aaa' -> false :) > cheers > Johan > _______________________________________________ > Pharo-project mailing list > [email protected] > http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project > -- Best regards, Igor Stasenko AKA sig. _______________________________________________ Pharo-project mailing list [email protected] http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
