Synopsis

template<
      typename First
    , typename Last
    >
struct distance
{
    typedef |unspecified| type;
};

Description

Returns the distance between First and Last iterators, that is, an |Integral Constant| n such that advance<First,n>::type is identical to Last.

Header

#include <boost/mpl/distance.hpp>

Parameters

Model Of

|Tag Dispatched Metafunction|

Expression semantics

For any |Forward Iterator|s first and last:

typedef distance<first,last>::type n;

typedef iter_fold<
      iterator_range<first,last>
    , long_<0>
    , next<_1>
    >::type n;

Complexity

Amortized constant time if first and last are |Random Access Iterator|s, otherwise linear time.

Example

typedef range_c<int,0,10>::type range;
typedef begin<range>::type first;
typedef end<range>::type last;
BOOST_MPL_ASSERT_RELATION( (distance<first,last>::value), ==, 10);

See also

|Iterators|, |Tag Dispatched Metafunction|, |advance|, |next|, |prior|