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> ));