| .. Algorithms/Querying Algorithms//find_if |20 |
| |
| find_if |
| ======= |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename Pred |
| > |
| struct find_if |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns an iterator to the first element in ``Sequence`` that satisfies |
| the predicate ``Pred``. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/find_if.hpp> |
| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-------------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===============================+===================================+ |
| | ``Sequence`` | |Forward Sequence| | A sequence to search in. | |
| +---------------+-------------------------------+-----------------------------------+ |
| | ``Pred`` | Unary |Lambda Expression| | A search condition. | |
| +---------------+-------------------------------+-----------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Forward Sequence| ``s`` and unary |Lambda Expression| ``pred``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef find_if<s,pred>::type i; |
| |
| :Return type: |
| |Forward Iterator|. |
| |
| :Semantics: |
| ``i`` is the first iterator in the range |begin/end<s>| such that |
| |
| .. parsed-literal:: |
| |
| apply< pred,deref<i>::type >::type::value == true |
| |
| If no such iterator exists, ``i`` is identical to ``end<s>::type``. |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. At most ``size<s>::value`` applications of ``pred``. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector<char,int,unsigned,long,unsigned long> types; |
| typedef find_if<types, is_same<_1,unsigned> >::type iter; |
| |
| BOOST_MPL_ASSERT(( is_same< deref<iter>::type, unsigned > )); |
| BOOST_MPL_ASSERT_RELATION( iter::pos::value, ==, 2 ); |
| |
| |
| See also |
| -------- |
| |
| |Querying Algorithms|, |find|, |count_if|, |lower_bound| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
