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protect is an identity wrapper for a Metafunction Class that prevents its argument from being recognized as a bind expression.
#include <boost/mpl/protect.hpp>
| Parameter | Requirement | Description |
|---|---|---|
| F | Metafunction Class | A metafunction class to wrap. |
For any Metafunction Class f:
typedef protect<f> g;
| Return type: | |
|---|---|
| Semantics: | If f is a bind expression, equivalent to
struct g
{
template<
typename U1 = unspecified,... typename Un = unspecified
>
struct apply
: apply_wrapn<f,U1,...Un>
{
};
};
otherwise equivalent to typedef f g;. |
FIXME
struct f
{
template< typename T1, typename T2 > struct apply
{
// ...
};
};
typedef bind<_1, protect< bind<f,_1,_2> > >
typedef apply_wrap0< f0 >::type r1;
typedef apply_wrap0< g0 >::type r2;
typedef apply_wrap2< f2,int,char >::type r3;
BOOST_MPL_ASSERT(( is_same<r1,char> ));
BOOST_MPL_ASSERT(( is_same<r2,char> ));
BOOST_MPL_ASSERT(( is_same<r3,char> ));