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From: volkert@nivoba.de (Volkert)
Newsgroups: comp.lang.eiffel,comp.lang.ada
Subject: Re: ANN: SPARK Book - Sample Chapters now free on-line
Date: 1 May 2003 05:54:51 -0700
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"Neil Groves" <neilgroves_no_spam@dial.pipex.com> wrote in message news:<vaqcvcruvo1493@corp.supernews.com>...
> I thought that SPARK required contra-variance which is fundamentally
> incompatible with the covariance in Eiffel?
There is no concept of contra-/co-variance in Spark. 
As i understand Spark, the redefinition of a procedure (method) 
in a child of a tagged type (class) must have >>exactly<< the 
same procdure signature as given with the parent type. A very 
strong conformance rule, but remember: Spark has NO references (entities) 
and NO dispatching (class wide types with offers you dynamic binding)

Volkert