empty

Synopsis

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

Description

シーケンスがemptyの時のみ，c::value == trueになるように，汎整数定数cを返す．

Definition

#include "boost/mpl/empty.hpp"

Parameters

Parameter	Requirement	Description
`Sequence`	Sequenceのモデル

Expression semantics

Expression Expression type Precondition Semantics Postcondition

typedef empty<Sequence>::type c; bool Integral Constantのモデル typedef is_same< begin<Sequence>::type,end<Sequence>::type >::type c;と等価

Expression	Expression type	Precondition	Semantics	Postcondition
`typedef empty<Sequence>::type c;`	`bool` Integral Constantのモデル		`typedef is_same< begin<Sequence>::type,end<Sequence>::type >::type c;`と等価

Complexity

償却定数時間

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)