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[Home]iter_fold

Synopsis

template<
      typename Sequence
    , typename State
    , typename ForwardOp
    >
struct iter_fold
{
    typedef unspecified type;
};

Description

Returns the result of the successive application of binary ForwardOp to the result of the previous ForwardOp invocation (State if it's the first call) and each iterator in the range [begin<Sequence>::type,end<Sequence>::type) in the linear order.

Definition

#include "boost/mpl/iter_fold.hpp"

Parameters

 Parameter  Requirement  Description  
SequenceA model of SequenceA sequence to iterate.
StateA typeThe initial state for the first ForwardOp application.
ForwardOpA model of [Lambda Function]The operation to be executed on forward traversal.

Expression semantics

 Expression  Expression type  Precondition  Semantics  Postcondition 
typedef iter_fold<Sequence,T,Op>::type t;A typeEquivalent to typedef lambda<Op>::type op; typedef begin<Sequence>::type i1; typedef apply<op,T,i1>::type t1; typedef i1::next i2; typedef apply<op,t1,i2>::type t2; ...; typedef apply<op,T,in>::type tn; typedef in::next last; typedef tn t, where n == size<Sequence>::type::value and last is identical to end<Sequence>::type; Equivalent to typedef T t; if the sequence is empty.

Complexity

Linear. Exactly size<Sequence>::type::value applications of ForwardOp.

Example

typedef list_c<int,5,-1,0,7,2,0,-5,4> numbers;
typedef iter_fold<
      numbers
    , begin<numbers>::type
    , if_< less< deref<_1>, deref<_2> >,_2,_1 >
    >::type max_element_iter;

BOOST_STATIC_ASSERT(max_element_iter::type::value == 7);

See also

Algorithms, iter_fold_backward, fold, fold_backward, copy, copy_backward


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Last edited July 19, 2002 1:16 am