Larry Evans wrote:
On 07/07/2007 11:49 AM, Eric Niebler wrote: [snip]
template<typename Expr> struct wrap { explicit wrap(Expr const &expr) {} };
Thanks very much Eric; however, I found that with the following:
template<typename Expr> struct wrap #define INHERIT_EXPR #ifdef INHERIT_EXPR : Expr #endif { explicit wrap(Expr const &expr) { std::cout<<"Wrap::CTOR\n"; } };
the wrap CTOR is not called when:
WrapItUp::call( _1 + _2, i, i );
is executed. OTOH, if INHERIT_EXPR is undefined, then wrap CTOR *is* called.
This is construct<> being too clever by a half. The expr<> struct doesn't have a constructor. It uses brace initialization. The construct<> transform tries to accommodate that by using brace initialization for things that look like Proto expressions. But I see now that it can't really know, so I should break this up into separate construct<> and pod_construct<> transforms. -- Eric Niebler Boost Consulting www.boost-consulting.com