On Mon, May 30, 2011 at 1:51 PM, Vicente BOTET <vicente.botet@wanadoo.fr>wrote:
Hi,
I've tried to add a configuration point in Boost.Conversion via overloading and ADL, but while the internal call of the library can find them using a trick that adds a parameter that contains the type of the return type, the user is not able to find them without using the same this trick, but this is too dark to be natural for user code.
Next follows a simplified code of the problem. The following
namespace N { struct S{};
template (*typename T*) T fct1(S const& s) { return T(s); } template (*typename T*) void fct2(T &t, S const& s) { t=s; } }
void test () { N::S s1; N::S s2; fct2(s2, s1); s2=fct1(*N::S*)(s1); // (1) }
Results in a compile error in (1)
error: ‘fct1’ was not declared in this scope
Is it standard behavior that fct1 can not be found by ADL?
Thanks, Vicente
P.S. Please replace (* and *) by angle brackets.
AFAIK, this is standard behavior. Explicitly providing template parameters to a function call (as well as namespace qualification and putting the function name in parentheses) disables ADL. I don't think you can provide an extension framework for Boost.Conversion without the result type appearing somewhere in the customization function's function parameters. I don't really view that as any "darker" than, say, using Boost.EnableIf, or any of a number of other TMP hacks...they are all constrained from a (perhaps) more ideal syntax and form by the constraints of the language. - Jeff