Problem with distance and STL map

[tron.thomas]

I have tried the following code on three different compilers and all
three produce programs that hang and fail to complete successfully.

#include <map>
#include <string>
#include <iostream>
#include <iterator>

int main()
{
typedef std::map<int, std::string> Values;
typedef Values::iterator Iterator;
Values values;

values[1] = "one";
values[2] = "two";
values[3] = "three";
values[4] = "four";
values[5] = "five";

Iterator first = values.find(4);
Iterator second = values.find(2);

std::cout << "The distance is " << std::distance(first, second) <<
".\n";

return 0;
}

I did not find any documentation that would indicate this should not
work.
How valid is the use of distance with an SLT map?

[Pete Becker]

tr*********@verizon.net wrote:

I did not find any documentation that would indicate this should not
work.
How valid is the use of distance with an SLT map?

For anything other than a random access iterator, distance increments
its first argument until it's equal to its second argument. Since the
first argument in the code follows the second argument, distance can't work.

--

Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)

[Ali Çehreli]

<tr*********@verizon.net> wrote in message
news:11*********************@o13g2000cwo.googlegro ups.com...

I have tried the following code on three different compilers and all
three produce programs that hang and fail to complete successfully.

#include <map>
#include <string>
#include <iostream>
#include <iterator>

int main()
{
typedef std::map<int, std::string> Values;
typedef Values::iterator Iterator;
Values values;

values[1] = "one";
values[2] = "two";
values[3] = "three";
values[4] = "four";
values[5] = "five";

Iterator first = values.find(4);
Iterator second = values.find(2);

std::cout << "The distance is " << std::distance(first, second) <<
".\n";

return 0;
}

I did not find any documentation that would indicate this should not
work.
How valid is the use of distance with an SLT map?

Like other standard algorithms, distance has no knowledge of containers. It
works with a pair of iterators. What your usage fails to meet is the
requirement that the second iterator must be reachable from the first
iterator.

Ali
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