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<P>&copy;Copyright 1996 Rogue Wave Software</P>
<H2>distance</H2>
<HR><PRE>     Iterator Operation</PRE><HR>
<A NAME="Summary"><H3>Summary</H3></A>
<P>Computes the distance between two iterators</P>
<PRE></PRE>
<H3>Contents</H3>
<UL>
<A HREF="#Synopsis"><LI>Synopsis</LI></A>
<A HREF="#Description"><LI>Description</LI></A>
<A HREF="#Example"><LI>Example</LI></A>
<A HREF="#Warning"><LI>Warning</LI></A>
<A HREF="#See Also"><LI>See Also</LI></A>
</UL>
<A NAME="Synopsis"><H3>Synopsis</H3></A>
<PRE>#include &#60;iterator></PRE>
<PRE>
template &#60;class InputIterator, class Distance>
 void distance (InputIterator first,
                InputIterator last,
                Distance&#38; n);</PRE>
<A NAME="Description"><H3>Description</H3></A>
<P>The <B><I>distance</B></I> template function computes the distance between two iterators and stores that value in <SAMP>n</SAMP>.  The last iterator must be reachable from the first iterator.</P>
<P><B><I>distance</B></I> increments <SAMP>n</SAMP> by the number of times it takes to get from <SAMP>first</SAMP> to <SAMP>last</SAMP>. <B><I>distance</B></I> must be a three argument function that stores the result into a reference instead of returning the result, because the distance type cannot be deduced from built-in iterator types such as<SAMP> int*</SAMP>.</P>
<A NAME="Example"><H3>Example</H3></A>
<PRE>//
// distance.cpp
//
 #include &#60;iterator>
 #include &#60;vector>
 #include &#60;iostream.h> 

int main()
 {
   //
   //Initialize a vector using an array
   //
   int arr[6] = {3,4,5,6,7,8};
   vector&#60;int> v(arr,arr+6);
   //
   //Declare a list iterator, s.b. a ForwardIterator
   //
   vector&#60;int>::iterator itr = v.begin()+3;
   //
   //Output the original vector
   //
   cout &#60;&#60; "For the vector: ";
   copy(v.begin(),v.end(),ostream_iterator&#60;int>(cout," "));
   cout &#60;&#60; endl &#60;&#60; endl;
   cout &#60;&#60; "When the iterator is initialized to point to "
        &#60;&#60; *itr &#60;&#60; endl;
   //
   // Use of distance
   //
   vector&#60;int>::difference_type dist = 0;
   distance(v.begin(), itr, dist);
   cout &#60;&#60; "The distance between the beginning and itr is " 
        &#60;&#60; dist &#60;&#60; endl;
   return 0;
 }
Output : 
For the vector: 3 4 5 6 7 8
When the iterator is initialized to point to 6
The distance between the beginning and itr is 3
</PRE>
<A NAME="Warning"><H3>Warning</H3></A>
<P>If your compiler does not support default template parameters then you need to always supply the <SAMP>Allocator</SAMP> template argument. For instance you'll have to write:</P>
<PRE>vector &#60;int, allocator></PRE>
<P>instead of:</P>
<PRE>vector &#60;int></PRE>
<A NAME="See Also"><H3>See Also</H3></A>
<P><A HREF="Seq_6405.htm"><B><I>Sequences</B></I></A>, <A HREF="Ran_7047.htm"><B><I>Random Access Iterators</B></I></A></P>
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