replace_if

Synopsis

template<
      typename Sequence
    , typename Pred
    , typename NewType
    >
struct replace_if
{
    typedef unspecified type;
};

Description

Performs a conditional replacement operation on the sequence. The algorithm returns a new sequence which contains all the elements from [begin<Sequence>::type, end<Sequence>::type) range where every type that satisfies the predicate Pred has been replaced with a NewType. The result sequence preserves all the functional and performance characteristics of the original Sequence, including its size, but not identity.

Definition

#include "boost/mpl/replace_if.hpp"

Parameters

Expression semantics

Expression	Expression type	Precondition	Semantics	Postcondition
typedef replace_if<Sequence,Pred,NewType>::type s;	A model of Extensible Sequence		Equivalent to typedef lambda<Pred>::type pred; typedef transform< Sequence, if_< apply1<pred,_1>,NewType,_1> >::type t;.

Complexity

Linear. Performs exactly size<Sequence>::type::value applications of Pred, and at most size<Sequence>::type::value insertions.

Example

typedef list_c<int,1,4,5,2,7,5,3,5>::type numbers;
typedef replace_if< numbers, greater<_,4>, int_<0> >::type result;
typedef list_c<int,1,4,0,2,0,0,3,0>::type answer;
BOOST_STATIC_ASSERT((equal< answer,result >::type::value));

See also

Algorithms, replace, transform