can not reference make_pair?

[John Black]

Hi,
I have this code piece,

vector<int> v1, v2;
vector<pair<int , int> > uups;
....

transform(v1.be gin(), v1.end(), v2.begin(), uups.end(),
ptr_fun(make_pa ir));

But my gcc compiler complains that "no matching function for call to
`ptr_fun(<unkno wn type>". Do you know what's wrong here?

Thanks.

[Jonathan Turkanis]

Re: can not reference make_pair?


"John Black" <black@eed.co m> wrote in message
news:cne57b$iv8 3@cliff.xsj.xil inx.com...[color=blue]
> Hi,
> I have this code piece,
>
> vector<int> v1, v2;
> vector<pair<int , int> > uups;
> ....
>
> transform(v1.be gin(), v1.end(), v2.begin(), uups.end(),
> ptr_fun(make_pa ir));[/color]

std::make_pair is a function template; to retrieve a function pointer to one of
its specializations you must use a cast or assign it to a function pointer
variable, as in the following:

#include <algorithm>
#include <functional>
#include <utility>
#include <vector>

using namespace std;

int main()
{
pair<int, int> (*make_int_pair ) (int, int) = make_pair;

vector<int> v1, v2;
vector<pair<int , int> > uups;
transform(v1.be gin(), v1.end(), v2.begin(), uups.end(),
ptr_fun(make_in t_pair));
}

One more thing: I'm not sure the standard guarantees that make_pair doesn't have
additional function parameters with default values. Probably someone else here
knows.
[color=blue]
> Thanks.[/color]

Jonathan

[ES Kim]

Re: can not reference make_pair?

"John Black" <black@eed.co m> wrote in message
news:cne57b$iv8 3@cliff.xsj.xil inx.com...[color=blue]
> Hi,
> I have this code piece,
>
> vector<int> v1, v2;
> vector<pair<int , int> > uups;
> ....
>
> transform(v1.be gin(), v1.end(), v2.begin(), uups.end(),
> ptr_fun(make_pa ir));
>
> But my gcc compiler complains that "no matching function for call to
> `ptr_fun(<unkno wn type>". Do you know what's wrong here?
>
> Thanks.[/color]

make_pair is not a function, just a template. But make_pair<int, int> is.
One more thing: you must "push_back" the result into uups, not just
placing it at the end.

transform(v1.be gin(), v1.end(), v2.begin(), back_inserter(u ups),
ptr_fun(make_pa ir<int, int>));

--
ES Kim