[boost] Re: Interesting Boost Implementation Details?

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-01-12 10:29:23

David Abrahams wrote:

> * The way that Boost.MPL uses partial specialization on template
> template parameters to peel apart lambda expressions and turn them into
> metafunction classes.

I thought I understand how it's done, but now that I am trying to apply this
to my own problem, it seems that default template parameters may be a
showstopper in applying this technique, at least in some compilers.  For
example if I have:

template<class T> struct do_something;

template<template<class> class T, class P0>
struct do_something<T<P0> >
{};

template<template<class, class> class T, class P0, class P1>
struct do_something<T<P0, P1> >
{};

GCC 3.4.2 can't figure out which specialization to use for, e.g.,
std::vector.  At the same time VC71 is fine with this, and chooses the one
with 2 parameteres.

Unfortunately I am unable to find my way around the MPL source to figure out
what's really done...

Can you clarify this?

Thanks in advance,
Arkadiy