develooper Front page | perl.perl6.language | Postings from March 2005

Re: Adding linear interpolation to an array

Thread Previous | Thread Next
From:
David Storrs
Date:
March 10, 2005 10:37
Subject:
Re: Adding linear interpolation to an array
Message ID:
20050310183708.GA58463@megazone.bigpanda.com
> At 17:53 +0100 3/10/05, Thomas Sandlaß wrote:
[request for clarification of 'covariant' and 'contravariant' usage]
> >'Co' means together like in coproduction. And 'contra' is the opposite
> >as in counterproductive. With instanciating parametric types the question
> >arises how a subtype relation between instanciating types propagates
> >to the template. E.g with Int <: Num, covariance would result in
> >Array[Int] <: Array[Num]. Referential classes are actually quite difficult
> >because upon write they are contravariant and covariant when read!
> >So a third case of uncomparable types is needed as well, or it is the default
> >if nothing else is specified.

Thomas,

I appreciate you attempting to explain this, but it remains clear as
mud, at least to me.  Could you please try again, using very short,
very non-technical words and not assuming a mathematical or
scientific background on the part of your reader?

Something that would help: We could all look the words up in a
dictionary, so we don't need a definition.  What we need is a
clarification, in simple terms, of what *you* mean by them, in this
context. 

Thank you.

--Dks

Thread Previous | Thread Next


nntp.perl.org: Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at ask@perl.org | Group listing | About