Re: Who discovered the type erasure technique in C++?

From:
Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org>
Newsgroups:
comp.lang.c++.moderated
Date:
Tue, 19 Aug 2008 03:41:33 CST
Message-ID:
<K5tqIp.MDx@beaver.cs.washington.edu>
marlow.andrew@googlemail.com wrote:

On 17 Aug, 15:48, "Roshan Naik" <naikr...@gmail.com> wrote:

   I am wondering who first figured out how to do this in C++ ?
Boost::Function and Boost::Expressive libraries both use it and my Castor
library (mpprogramming.com/cpp) also relies on it very heavily. I thought
Eric Niebler might be the one, but at NWCPP he told me that he too had
picked it up from somewhere else.


I have never heard of type erasure in C++. I have come across it in
java though. I always thought it was there for compatibility with
containers before java had generics. What exactly does it mean in C++
please?

Regards,

Andrew Marlow


Without being called as such, it's of use in the implementation of
Variant (www.oonumerics.org/tmpw01/alexandrescu.pdf, see also three
subsequent articles http://www.erdani.org/publications/cuj-04-2002.html,
http://www.erdani.org/publications/cuj-06-2002.html,
http://www.erdani.org/publications/cuj-08-2002.html).

What gives it away in C++ is a type with a template constructor that
uses the type to create a dynamically polymorphic object.

Andrei

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