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From: Rob Stewart (stewart_at_[hidden])
Date: 2005-03-05 10:32:23

From: "Richard Peters" <r.a.peters_at_[hidden]>
> The bigint type proposed for the C++ standard library does not permit the
> use of expression templates. Using expression templates has a positive and a
> negative aspect: A significant speedup can be gained using expression
> templates. The downside is that templates cannot deduce the correct type of
> expressions, for example:
> template<class T> void f(T a, T b) will not work when invoked as f(x + y,
> x - y), because x + y returns an object of type different from x - y.
> Because the C++ standard library proposal specifies the result type of the
> operators to be of type const integer, a library implementing that proposal
> cannot use expression templates.

PMFJI, but I wonder whether this would work:

   template <typename T, typename U>
   void f(T a, U b)
      typedef typename <magical_incantation<T, U>::type V;
      f_impl<V>(a, b);

a and b can have different types, but then magical_incantation
computes a common type to which both can be converted and the
implementation function can be invoked with that type.

I may be off base, and you may have already tried this approach,
but I just wanted to mention it if it could help.

Rob Stewart                           stewart_at_[hidden]
Software Engineer           
Susquehanna International Group, LLP  using std::disclaimer;

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