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

   1 .. Algorithms/Querying Algorithms//find_if |20
   2
   3 find_if
   4 =======
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename Sequence
  13         , typename Pred
  14         >
  15     struct find_if
  16     {
  17         typedef |unspecified| type;
  18     };
  19
  20
  21
  22 Description
  23 -----------
  24
  25 Returns an iterator to the first element in ``Sequence`` that satisfies
  26 the predicate ``Pred``.
  27
  28
  29 Header
  30 ------
  31
  32 .. parsed-literal::
  33
  34     #include <boost/mpl/find_if.hpp>
  35
  36
  37
  38 Parameters
  39 ----------
  40
  41 +---------------+-------------------------------+-----------------------------------+
  42 | Parameter     | Requirement                   | Description                       |
  43 +===============+===============================+===================================+
  44 | ``Sequence``  | |Forward Sequence|            | A sequence to search in.          |
  45 +---------------+-------------------------------+-----------------------------------+
  46 | ``Pred``      | Unary |Lambda Expression|     | A search condition.               |
  47 +---------------+-------------------------------+-----------------------------------+
  48
  49
  50 Expression semantics
  51 --------------------
  52
  53 For any |Forward Sequence| ``s`` and unary |Lambda Expression| ``pred``:
  54
  55
  56 .. parsed-literal::
  57
  58     typedef find_if<s,pred>::type i;
  59
  60 :Return type:
  61     |Forward Iterator|.
  62
  63 :Semantics:
  64     ``i`` is the first iterator in the range |begin/end<s>| such that
  65
  66     .. parsed-literal::
  67
  68         apply< pred,deref<i>::type >::type::value == true
  69
  70     If no such iterator exists, ``i`` is identical to ``end<s>::type``.
  71
  72
  73 Complexity
  74 ----------
  75
  76 Linear. At most ``size<s>::value`` applications of ``pred``.
  77
  78
  79 Example
  80 -------
  81
  82 .. parsed-literal::
  83
  84     typedef vector<char,int,unsigned,long,unsigned long> types;
  85     typedef find_if<types, is_same<_1,unsigned> >::type iter;
  86
  87     BOOST_MPL_ASSERT(( is_same< deref<iter>::type, unsigned > ));
  88     BOOST_MPL_ASSERT_RELATION( iter::pos::value, ==, 2 );
  89
  90
  91 See also
  92 --------
  93
  94 |Querying Algorithms|, |find|, |count_if|, |lower_bound|
  95
  96
  97 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  98    Distributed under the Boost Software License, Version 1.0. (See accompanying
  99    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)