Subject: [Boost-users] [boost::format] operator % could use call_traits<..>::parameter_type
From: Luc Bourhis (luc_j_bourhis_at_[hidden])
Date: 2012-06-24 19:22:32
Hi,
consider a library featuring code like
template <..., unsigned Rank, ...> struct Foo { ... static unsigned const rank = Rank; .... };
as well as
boost::format(...) % Foo::rank
Such code will link if and only if a definition for Foo::rank is provided because the interface of operator % is
template <class T>
operator%(const T& x)
This is not possible in the library, as I do not know which values of Rank will be used by client code. Thus the only possibility is a hat trick like
boost::format(...) % (Foo::rank+0)
If operator % took integral types by value instead, this would alleviate the problem. Hence the suggestion to use call_traits<T>::parameter_type instead of T const &.
Of course, the same could be said of many functions other than format::operator%
Best wishes,
Luc Bourhis