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Re: Re: [v3] PATCH: PR 20599 (variadic templates, take two) (4/4)

On 9/20/06, Paolo Carlini <> wrote:
Douglas Gregor wrote:

> This is part 4 of 4. It contains changes to libstdc++'s TR1
> implementation to make full use of variadic templates, eliminating
> all of the preprocessor metaprogramming that we're using now.

+  // Define a large number of placeholders. There is no way to
+  // simplify this with variadic templates, because we're introducing
+  // unique names for each.
+  namespace placeholders { namespace {
+    _Placeholder<1> _1;
[snip gazillions of placeholders]
+ } }

Certainly a minor nit, but I'm curious about this issue: are there any concrete plans to address it? Seems strange to have it in the final standard, I never saw something similar before...

I don't know of any plans to address this issue. TR1 basically just says that there are objects _1, _2, _3, etc. (up to _10, at least). Since each has a unique name, we'd need some kind of language solution to get rid of the repetition. It doesn't fit into variadic templates at all; I can't even think of anywhere it does fit.


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