ceph/src/boost/libs/mpl/doc/src/refmanual/erase_key.rst

   1 .. Sequences/Intrinsic Metafunctions//erase_key
   2
   3 erase_key
   4 =========
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename AssocSeq
  13         , typename Key
  14         >
  15     struct erase_key
  16     {
  17         typedef |unspecified| type;
  18     };
  19
  20
  21
  22 Description
  23 -----------
  24
  25 Erases elements associated with the key ``Key`` in the |Extensible Associative Sequence|
  26 ``AssocSeq`` .
  27
  28 Header
  29 ------
  30
  31 .. parsed-literal::
  32
  33     #include <boost/mpl/erase_key.hpp>
  34
  35
  36 Model of
  37 --------
  38
  39 |Tag Dispatched Metafunction|
  40
  41
  42 Parameters
  43 ----------
  44
  45 +---------------+-----------------------------------+-----------------------------------------------+
  46 | Parameter     | Requirement                       | Description                                   |
  47 +===============+===================================+===============================================+
  48 | ``AssocSeq``  | |Extensible Associative Sequence| | A sequence to erase elements from.            |
  49 +---------------+-----------------------------------+-----------------------------------------------+
  50 | ``Key``       | Any type                          | A key for the elements to be removed.         |
  51 +---------------+-----------------------------------+-----------------------------------------------+
  52
  53
  54 Expression semantics
  55 --------------------
  56
  57 For any |Extensible Associative Sequence| ``s``, and arbitrary type ``key``:
  58
  59
  60 .. parsed-literal::
  61
  62     typedef erase_key<s,key>::type r;
  63
  64 :Return type:
  65     |Extensible Associative Sequence|.
  66
  67 :Semantics:
  68     ``r`` is |concept-identical| and equivalent to ``s`` except that
  69     ``has_key<r,k>::value == false``.
  70
  71 :Postcondition:
  72     ``size<r>::value == size<s>::value - 1``.
  73
  74
  75
  76 Complexity
  77 ----------
  78
  79 Amortized constant time.
  80
  81
  82 Example
  83 -------
  84
  85 .. parsed-literal::
  86
  87     typedef map< pair<int,unsigned>, pair<char,long> > m;
  88     typedef erase_key<m,char>::type m1;
  89
  90     BOOST_MPL_ASSERT_RELATION( size<m1>::type::value, ==, 1 );
  91     BOOST_MPL_ASSERT(( is_same< at<m1,char>::type,void\_ > ));
  92     BOOST_MPL_ASSERT(( is_same< at<m1,int>::type,unsigned > ));
  93
  94
  95 See also
  96 --------
  97
  98 |Extensible Associative Sequence|, |erase|, |has_key|, |insert|
  99
 100
 101 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 102    Distributed under the Boost Software License, Version 1.0. (See accompanying
 103    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)