в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

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2010-05-25T10:29:31Z

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==Advance the iterator==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <list>
#include <algorithm>
using namespace std;
int main()
{
list<int> coll;
// insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll.push_back(i);
}
list<int>::iterator pos = coll.begin();
// print actual element
cout << *pos << endl;
// step three elements forward
advance (pos, 3);
// print actual element
cout << *pos << endl;
// step one element backward
advance (pos, -1);
// print actual element
cout << *pos << endl;
}</source>
<pre class=codeResult>1
4
3</pre>

==Convert iterator to reverse iterator==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector<int> coll;
// insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll.push_back(i);
}
// find position of element with value 5
vector<int>::iterator pos;
pos = find (coll.begin(), coll.end(),
5);
// print value to which iterator pos refers
cout << "pos: " << *pos << endl;
// convert iterator to reverse iterator rpos
vector<int>::reverse_iterator rpos(pos);
// print value to which reverse iterator rpos refers
cout << "rpos: " << *rpos << endl;
}</source>
<pre class=codeResult>pos: 5
rpos: 4</pre>

==Find a value in map by key==

<source lang="cpp">#include <iostream>
#include <map>
using namespace std;
int main()
{
map<char, int> m;
// put pairs into map
for(int i=0; i<26; i++) {
m.insert(pair<char, int>("A"+i, 65+i));
}
char ch = "G";
map<char, int>::iterator p;

// find value given key
p = m.find(ch);
if(p != m.end())
cout << "Its ASCII value is " << p->second;
else
cout << "Key not in map.\n";
return 0;
}</source>
<pre class=codeResult>Its ASCII value is 71</pre>

==iterator template==

<source lang="cpp">#include <vector>
#include <iterator>
#include <iostream>
using std::vector;
using std::cout;
using std::endl;
template <typename IteratorType>
void iteratorTraitsTest(IteratorType it)
{
typename std::iterator_traits<IteratorType>::value_type temp;
temp = *it;
cout << temp << endl;
}
int main(int argc, char** argv)
{
vector<int> v;
v.push_back(5);
iteratorTraitsTest(v.begin());
return (0);
}</source>

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в 14:21, 25 мая 2010

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