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source: downloads/boost_1_34_1/libs/mpl/doc/src/refmanual/distance.rst @ 29

Last change on this file since 29 was 29, checked in by landauf, 17 years ago

updated boost from 1_33_1 to 1_34_1
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distance

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.

Parameters

Parameter Requirement Description
First, Last |Forward Iterator| Iterators to compute a distance between.

Expression semantics

For any |Forward Iterator|s first and last:

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

|Integral Constant|.
Precondition:

[first, last) is a valid range.
Semantics:

Equivalent to

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

is_same< advance<first,n>::type, last >::value == true.

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);

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