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Front Page / Metafunctions / Logical Operations / and_

and_

Synopsis

template<
      typename F1
    , typename F2
    ...
    , typename Fn = unspecified
    >
struct and_
{
    typedef unspecified type;
};

Description

Returns the result of short-circuit logical and (&&) operation on its arguments.

Header

#include <boost/mpl/and.hpp>
#include <boost/mpl/logical.hpp>

Parameters

Parameter Requirement Description
F1, F2,... Fn Nullary Metafunction Operation's arguments.

Expression semantics

For arbitrary nullary Metafunctions f1, f2,... fn:

typedef and_<f1,f2,...,fn>::type r;
Return type:Integral Constant.
Semantics:r is false_ if either of f1::type::value, f2::type::value,... fn::type::value expressions evaluates to false, and true_ otherwise; guarantees left-to-right evaluation; the operands subsequent to the first fi metafunction that evaluates to false are not evaluated.
typedef and_<f1,f2,...,fn> r;
Return type:

Integral Constant.

Semantics:

Equivalent to

struct r : and_<f1,f2,...,fn>::type {};

Example

struct unknown;

BOOST_MPL_ASSERT(( and_< true_,true_ > ));
BOOST_MPL_ASSERT_NOT(( and_< false_,true_ > ));
BOOST_MPL_ASSERT_NOT(( and_< true_,false_ > ));
BOOST_MPL_ASSERT_NOT(( and_< false_,false_ > ));
BOOST_MPL_ASSERT_NOT(( and_< false_,unknown > )); // OK
BOOST_MPL_ASSERT_NOT(( and_< false_,unknown,unknown > )); // OK too

See also

Metafunctions, Logical Operations, or_, not_