There have been lots of proposals to fix the CATCALL problems in recent years. None have been implemented (at least in ISE/GEC compilers. And tecomp has been abandonded by its author - he is now writing a series of blogs about a vapourware product called "Modern Eiffel").
I don't find the CATCALL problem a great problem in practice (one gets used to avoiding the problem). But it is a nasty whole in the theory of the type system. On 3 January 2013 22:07, Timon Gehr <timon.g...@gmx.ch> wrote: > On 01/02/2013 11:19 PM, MigMit wrote: > >> >> On Jan 3, 2013, at 2:09 AM, Gershom Bazerman <gersh...@gmail.com> wrote: >> >> On 1/2/13 4:29 PM, MigMit wrote: >>> >>>> >>>> BTW. Why you think that Eiffel type system is unsafe? >>>>> >>>> Well, if I remember correctly, if you call some method of a certain >>>> object, and this call compiles, you can't be certain that this object >>>> actually has this method. Could be that this object belongs to some >>>> subclass which removes this method. >>>> >>>> >>> Eiffel doesn't handle the relationship of co- and contra-variance of >>> arguments with subtyping in a principled way. This is apparently known as >>> the "catcall" problem. See, e.g., this article: >>> http://www.eiffelroom.org/**node/517<http://www.eiffelroom.org/node/517> >>> >> >> Yes, variance is another big source of unsafety, that's for sure. And >> another reason I think there is no real "theory" behind Eiffel, just a >> bunch of features (or "concepts") boiled together. >> >> > There seem to be efforts to fix this: > http://tecomp.sourceforge.net/**index.php?file=doc/papers/**proof/<http://tecomp.sourceforge.net/index.php?file=doc/papers/proof/> > > The resulting language appears to be type safe: > http://tecomp.sourceforge.net/**index.php?file=doc/papers/** > lang/modern_eiffel.txt#**chapter_20<http://tecomp.sourceforge.net/index.php?file=doc/papers/lang/modern_eiffel.txt#chapter_20> > > > > > > ______________________________**_________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/**mailman/listinfo/haskell-cafe<http://www.haskell.org/mailman/listinfo/haskell-cafe> >
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe