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Front Page / Algorithms / Iteration Algorithms / iter_fold

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 order.

Header

#include <boost/mpl/iter_fold.hpp>

Parameters

Parameter Requirement Description
Sequence Forward Sequence A sequence to iterate.
State Any type The initial state for the first ForwardOp application.
ForwardOp Binary Lambda Expression The operation to be executed on forward traversal.

Expression semantics

For any Forward Sequence s, binary Lambda Expression op, and an arbitrary type state:

typedef iter_fold<s,state,op>::type t; 
Return type:A type.
Semantics:

Equivalent to

typedef begin<Sequence>::type i1;
typedef apply<op,state,i1>::type state1;
typedef next<i1>::type i2;
typedef apply<op,state1,i2>::type state2;
...
typedef apply<op,staten-1,in>::type staten; 
typedef next<in>::type last; 
typedef staten t;

where n == size<s>::value and last is identical to end<s>::type; equivalent to typedef state t; if empty<s>::value == true.

Complexity

Linear. Exactly size<s>::value applications of op.

Example

typedef vector_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_MPL_ASSERT_RELATION( deref<max_element_iter>::type::value, ==, 7 );

See also

Algorithms, reverse_iter_fold, fold, reverse_fold, copy