Setting first and second of pair<>

[pmatos]

Hi all,

Is there a way of (after creating a pair) set its first and second
element of not? (pair is definitely a read-only struct)?

Cheers,

Paulo Matos

[John Carson]

"pmatos" <po**@sat.inesc-id.pt> wrote in message
news:11**********************@f14g2000cwb.googlegr oups.com

Hi all,

Is there a way of (after creating a pair) set its first and second
element of not? (pair is definitely a read-only struct)?

#include <iostream>
#include <utility>
using namespace std;

int main()
{
std::pair<int, const char *> p;
p.first = 5;
p.second = "C-style string";
cout << p.first << endl;
cout << p.second << endl;
}
--
John Carson

[Rolf Magnus]

pmatos wrote:

Hi all,

Is there a way of (after creating a pair) set its first and second
element of not?
Yes.

#include <utility>
#include <iostream>

int main()
{
std::pair<int, int> p(1,2);
std::cout << p.first << '/' << p.second << '\n';
p.first = 3;
p.second = 5;
std::cout << p.first << '/' << p.second << '\n';
}
(pair is definitely a read-only struct)?

It is not. What makes you think so?

[pmatos]

John Carson wrote:

"pmatos" <po**@sat.inesc-id.pt> wrote in message
news:11**********************@f14g2000cwb.googlegr oups.com

Hi all,

Is there a way of (after creating a pair) set its first and second
element of not? (pair is definitely a read-only struct)?
#include <iostream>
#include <utility>
using namespace std;

int main()
{
std::pair<int, const char *> p;
p.first = 5;
p.second = "C-style string";
cout << p.first << endl;
cout << p.second << endl;
}

That's wierd.
If I have:
list<pair<int, int> > l;
l.push_back(pair<int,int>(1,1));
l.begin()->first = 2;

Says the pair is a read-only structure.

Any ideas?
--
John Carson

[John Carson]

"pmatos" <po**@sat.inesc-id.pt> wrote in message
news:11**********************@g49g2000cwa.googlegr oups.com

John Carson wrote:

#include <iostream>
#include <utility>
using namespace std;

int main()
{
std::pair<int, const char *> p;
p.first = 5;
p.second = "C-style string";
cout << p.first << endl;
cout << p.second << endl;
}

That's wierd.
If I have:
list<pair<int, int> > l;
l.push_back(pair<int,int>(1,1));
l.begin()->first = 2;

Says the pair is a read-only structure.

If that is your exact code, then it should work. So either your compiler /
library version is broken or this is not your exact code.

What happens with:

list<int > l;
l.push_back(1);
*l.begin() = 2;

?

--
John Carson

[benben]

That's wierd.
If I have:
list<pair<int, int> > l;
l.push_back(pair<int,int>(1,1));
or l.push_back(make_pair(1, 1));
l.begin()->first = 2;

Says the pair is a read-only structure.

Any ideas?

I compiled the code and it runs fine. Is it a compiler-error? "read-only
structure" is not a common term to me.

[pmatos]

Thanks all, the problems was that I was accessing it through
const_iterator to list. :)

Cheers,

Paulo Matos

benben wrote:

That's wierd.
If I have:
list<pair<int, int> > l;
l.push_back(pair<int,int>(1,1));

or l.push_back(make_pair(1, 1));

l.begin()->first = 2;

Says the pair is a read-only structure.

Any ideas?

I compiled the code and it runs fine. Is it a compiler-error? "read-only
structure" is not a common term to me.