On Jan 3, 2013, at 2:09 AM, Gershom Bazerman
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
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.