On 07/27/12 13:08, Steven Watanabe wrote:
AMDG
On 07/27/2012 09:49 AM, Larry Evans wrote:
The attached, when compiled with:
#define CONSTRUCTIBLE_PH
fails compilation despite satisfying this Concept constraint mentioned above.
It doesn't satisfy the requirements.
However, when:
//#define CONSTRUCTIBLE_PH
it compiles & runs OK. The compiling version just doesn't use a placeholder in the args to Sig of constructible.
Why doesn't the one with the placeholder in the Sig args compile? Maybe I'm not understanding what's meant by:
Concept must contain a matching instance of constructible.
Could you please explain what I'm missing?
You're passing an argument of type ph_value<_a>. How would constructible<_a(const _a&)> (which is the copy constructor) be viable?
Because, when _a in constructible<_a(const _a&)> is replaced by the binding, it becomes, IIUC, constructible<ph_value<_a>(const ph_value<_a>&)> and this is the same as the compiling version of binding_of.cpp. I thought this replacement is what would happen based on the example: constructible<_a(const _b&, const _c&)> from: http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... Why is the replacement done in the construction.html example and not in bindings_of.cpp? Hmmm... Ok, the example has any args, from which the bindings<ConceptA> can be gotten. But those same bindings are available from the binding<ConceptA> arg in bindings_of.cpp creation of a_dup. Obviously I'm still missing something, but I've no clue what :( Any help would be appreciated. -regards, Larry