Re: Sharing generic bodies across instantiations.

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 28 Lip, 18:32, "Peter C. Chapin" <pcc482...@gmail.com> wrote:

> The C++ community doesn't talk much
> about a shared implementation of templates. Is that because it's just
> unreasonably difficult in C++?

Or maybe just pointless, regardless of the difficulty.

I don't see any reason for doing it, really. The only possible reason
would be to minimize the size of executable, possibly targeting some
very constrained environment, but there are ways to do it more
efficiently than with code sharing in templates - the technique, based
on making a facade template implemented in terms of non-template
actual code, was described by Scott Meyers, although at the moment I
don't remember exactly which of his book covered it. The major
advantage of this technique was *no performance penalty*. That is -
small *and* fast code.

In other words, the real reason for not having such compiler
implementations might be that simply nobody needs them. Imagine
yourself as a compiler vendor and try to answer a question if it makes
sense to invest effort in this implementation strategy. If nobody asks
for it, then probably not - and the market position of those Ada
compilers that do it (code sharing) when compared to those that don't
might indicate that this technique is not terribly shaking the Ada
community either.

--
Maciej Sobczak * http://www.inspirel.com

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