erase_key

Synopsis

template<
      typename AssocSeq
    , typename Key
    >
struct erase_key
{
    typedef unspecified type;
};

Description

Erases elements associated with the key Key in the Extensible Associative Sequence AssocSeq .

Header

#include <boost/mpl/erase_key.hpp>

Model of

Tag Dispatched Metafunction

Parameters

Parameter	Requirement	Description
`AssocSeq`	Extensible Associative Sequence	A sequence to erase elements from.
`Key`	Any type	A key for the elements to be removed.

Expression semantics

For any Extensible Associative Sequence s, and arbitrary type key:

typedef erase_key<s,key>::type r;

Return type:	Extensible Associative Sequence.
Semantics:	`r` is concept-identical and equivalent to `s` except that `has_key<r,k>::value == false`.
Postcondition:	`size<r>::value == size<s>::value - 1`.

Complexity

Amortized constant time.

Example

typedef map< pair<int,unsigned>, pair<char,long> > m;
typedef erase_key<m,char>::type m1;

BOOST_MPL_ASSERT_RELATION( size<m1>::type::value, ==, 1 );
BOOST_MPL_ASSERT(( is_same< at<m1,char>::type,void_ > ));
BOOST_MPL_ASSERT(( is_same< at<m1,int>::type,unsigned > ));