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From: cs450a03@uc780.umd.edu
Newsgroups: comp.lang.misc,comp.object,comp.lang.eiffel
Subject: RE: CHALLENGE: heterogeneous collections
Message-ID: <27MAR91.23472366@uc780.umd.edu>
Date: 27 Mar 91 23:47:23 GMT
References: <1991Mar25.220525.11087@leland.Stanford.EDU> <1991Mar26.101051.29527@irisa.fr> <519@eiffel.UUCP> <1991Mar28.030354.25051@leland.Stanford.EDU>
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Urs Hoelzle writes:
>Suppose you have two classes T and SubT, where SubT is a subtype of T
>(in the strict sense of `subtype').  You also have the lists
> ...
>Now the problem: List[T] is not a subtype of List[SubT] because of the
>insert method (contravariance).  Thus, someProc(listB) is illegal even
> ...

That's not a problem, that's a slice of code.

Raul Rockwell