empty

Synopsis

template<
      typename Sequence
    >
struct empty
{
    typedef unspecified type;
};

Description

Returns an Integral Constant c such that c::value == true if and only if the sequence is empty.

Definition

#include "boost/mpl/empty.hpp"

Parameters

Expression semantics

Expression	Expression type	Precondition	Semantics	Postcondition
typedef empty<Sequence>::type c;	A model of bool Integral Constant		Equivalent to typedef is_same< begin<Sequence>::type,end<Sequence>::type >::type c;

Complexity

Amortized constant time.

Example

typedef range_c<int,0,0> empty_range;
typedef list<long,float,double> types;

BOOST_STATIC_ASSERT(empty<empty_range>::value)
BOOST_STATIC_ASSERT(!empty<types>::value)

See also

Sequence, size, begin, end