Synopsis

template<
      typename Sequence
    , typename State
    , typename ForwardOp
    >
struct 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 every element of the sequence in the range |begin/end<Sequence>| in order.

Header

#include <boost/mpl/fold.hpp>

Parameters

Expression semantics

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

typedef fold<s,state,op>::type t;

typedef iter_fold< s,state,apply<op,_1,deref<_2> > >::type t;

Complexity

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

Example

typedef vector<long,float,short,double,float,long,long double> types;
typedef fold<
      types
    , int_<0>
    , if_< is_float<_2>,next<_1>,_1 >
    >::type number_of_floats;
BOOST_MPL_ASSERT_RELATION( number_of_floats::value, ==, 4 );

See also

|Algorithms|, |accumulate|, |reverse_fold|, |iter_fold|, |reverse_iter_fold|, |copy|, |copy_if|