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Front Page / Algorithms / Transformation Algorithms / reverse_copy_if

reverse_copy_if

Synopsis

template<
      typename Sequence
    , typename Pred
    , typename In = unspecified
    >
struct reverse_copy_if
{
    typedef unspecified type;
};

Description

Returns a reversed, filtered copy of the original sequence containing the elements that satisfy the predicate Pred.

[Note: This wording applies to a no-inserter version(s) of the algorithm. See the Expression semantics subsection for a precise specification of the algorithm's details in all cases — end note]

Header

#include <boost/mpl/copy_if.hpp>

Model of

Reversible Algorithm

Parameters

Parameter Requirement Description
Sequence Forward Sequence A sequence to copy.
Pred Unary Lambda Expression A copying condition.
In Inserter An inserter.

Expression semantics

The semantics of an expression are defined only where they differ from, or are not defined in Reversible Algorithm.

For any Forward Sequence s, an unary Lambda Expression pred, and an Inserter in:

typedef reverse_copy_if<s,pred,in>::type r; 
Return type:A type
Semantics:

Equivalent to

typedef lambda<pred>::type p;
typedef lambda<in::operation>::type op;

typedef reverse_fold<
      s
    , in::state
    , eval_if<
          apply_wrap1<p,_2>
        , apply_wrap2<op,_1,_2>
        , identity<_1>
        >
    >::type r;

Complexity

Linear. Exactly size<s>::value applications of pred, and at most size<s>::value applications of in::operation.

Example

typedef reverse_copy_if<
      range_c<int,0,10>
    , less< _1, int_<5> >
    , front_inserter< vector<> >
    >::type result;

BOOST_MPL_ASSERT_RELATION( size<result>::value, ==, 5 );
BOOST_MPL_ASSERT(( equal<result,range_c<int,0,5> > ));

See also

Transformation Algorithms, Reversible Algorithm, copy_if, reverse_copy, remove_if, replace_if