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BOOST_MPL_HAS_XXX_TEMPLATE_DEF

Synopsis

#define BOOST_MPL_HAS_XXX_TEMPLATE_DEF(name) \
    unspecified token sequence \
/**/

Description

Expands into the definition of a boolean Metafunction has_name such that for any type x has_name<x>::value == true if and only if x is a class type and has a nested template member x::template name with no more than BOOST_MPL_LIMIT_METAFUNCTION_ARITY parameters.

On deficient compilers not capable of performing the detection, has_name<x>::value is always false. A boolean configuration macro, BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE, is provided to signal or override the "deficient" status of a particular compiler.

[Note: BOOST_MPL_HAS_XXX_TEMPLATE_DEF is a simplified front end to the BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF introspection macro — end note]

Header

#include <boost/mpl/has_xxx.hpp>

Parameters

Parameter Requirement Description
name A legal identifier token A name of the template member being detected.

Expression semantics

For any legal C++ identifier name:

BOOST_MPL_HAS_XXX_TEMPLATE_DEF(name)
Precondition:

Appears at namespace scope.

Return type:

None.

Semantics:

Equivalent to

BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF(
      BOOST_PP_CAT(has_,name), name, false
    )

Example

BOOST_MPL_HAS_XXX_TEMPLATE_DEF(xxx)

struct test1  {};
struct test2  { void xxx(); };
struct test3  { int xxx; };
struct test4  { static int xxx(); };
struct test5  { typedef int xxx; };
struct test6  { struct xxx; };
struct test7  { typedef void (*xxx)(); };
struct test8  { typedef void (xxx)(); };
struct test9  { template< class T > struct xxx {}; };

BOOST_MPL_ASSERT_NOT(( has_xxx<test1> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test2> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test3> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test4> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test5> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test6> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test7> ));
BOOST_MPL_ASSERT_NOT(( has_xxx<test8> ));

#if !defined(BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE)
BOOST_MPL_ASSERT(( has_xxx<test9> ));
#endif

BOOST_MPL_ASSERT(( has_xxx<test9, true_> ));

See also

Macros, BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF, BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE, BOOST_MPL_LIMIT_METAFUNCTION_ARITY