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Front Page / Iterators / Iterator Metafunctions / advance

advance

Synopsis

template<
      typename Iterator
    , typename N
    >
struct advance
{
    typedef unspecified type;
};

Description

Moves Iterator by the distance N. For bidirectional and random access iterators, the distance may be negative.

Header

#include <boost/mpl/advance.hpp>

Parameters

Parameter Requirement Description
Iterator Forward Iterator An iterator to advance.
N Integral Constant A distance.

Model Of

Tag Dispatched Metafunction

Expression semantics

For a Forward Iterator iter and arbitrary Integral Constant n:

typedef advance<iter,n>::type j;
Return type:

Forward Iterator.

Precondition:

If Iterator is a Forward Iterator, n::value must be nonnegative.

Semantics:

Equivalent to:

typedef iter i0;
typedef next<i0>::type i1;
...
typedef next<in-1>::type j;

if n::value > 0, and

typedef iter i0;
typedef prior<i0>::type i1;
...
typedef prior<in-1>::type j;

otherwise.

Postcondition:

j is dereferenceable or past-the-end; distance<iter,j>::value == n::value if n::value > 0, and distance<j,iter>::value == n::value otherwise.

Complexity

Amortized constant time if iter is a model of Random Access Iterator, otherwise linear time.

Example

typedef range_c<int,0,10> numbers;
typedef begin<numbers>::type first;
typedef end<numbers>::type last;

typedef advance<first,int_<10> >::type i1;
typedef advance<last,int_<-10> >::type i2;

BOOST_MPL_ASSERT(( boost::is_same<i1,last> ));
BOOST_MPL_ASSERT(( boost::is_same<i2,first> ));

See also

Iterators, Tag Dispatched Metafunction, distance, next