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Front Page / Sequences / Intrinsic Metafunctions / clear

clear

Synopsis

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

Description

Returns an empty sequence concept-identical to Sequence.

Header

#include <boost/mpl/clear.hpp>

Model of

Tag Dispatched Metafunction

Parameters

Parameter Requirement Description
Sequence Extensible Sequence or Extensible Associative Sequence A sequence to get an empty "copy" of.

Expression semantics

For any Extensible Sequence or Extensible Associative Sequence s:

typedef clear<s>::type t; 
Return type:Extensible Sequence or Extensible Associative Sequence.
Semantics:

Equivalent to

typedef erase< s, begin<s>::type, end<s>::type >::type t;
Postcondition:empty<s>::value == true.

Complexity

Amortized constant time.

Example

typedef vector_c<int,1,3,5,7,9,11> odds;
typedef clear<odds>::type nothing;

BOOST_MPL_ASSERT(( empty<nothing> ));

See also

Extensible Sequence, Extensible Associative Sequence, erase, empty, begin, end