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How to use std::copy with std::map?

P: n/a
Should the following work? It does on some compilers. How can I get it to
work on g++ 3.2?
On g++ 3.2 it keeps telling me that there is no such function operator <<
for ostream and pair<string,string>. But there is!
And I can call it! And it works! So why cannot std::copy find it?

thanks,
Siegfried

template<typename K, typename V>
ostream& operator<<(ostream& os, std::pair<K,V>& p){ return os << p.first <<
p.second; }

std::map<string,string> m; m[(string)"hello"] = (string)"there";
std::copy(m.begin(), m.end(), ostream_iterator<std::pair<string,string>
(cout, ",");

May 3 '06 #1
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P: n/a
Siegfried Heintze wrote:
Should the following work? It does on some compilers. How can I get
it to work on g++ 3.2?
Compiler-specific questions should be asked in the newsgroup dedicated
to that compiler. Try gnu.g++.help.
On g++ 3.2 it keeps telling me that there is no such function
operator << for ostream and pair<string,string>. But there is!
Where?
And I can call it! And it works! So why cannot std::copy find it?

thanks,
Siegfried

template<typename K, typename V>
ostream& operator<<(ostream& os, std::pair<K,V>& p){ return os <<
p.first << p.second; }
Is that what you wrote? Where does this definition appear? In
the global scope?
std::map<string,string> m; m[(string)"hello"] = (string)"there";
std::copy(m.begin(), m.end(),
ostream_iterator<std::pair<string,string>
(cout, ",");


Argument-dependent lookup (ADL) does not look in all the namespaces.
It limits its search to the types involved and the namespaces where
those types are defined. You need to place your operator in 'std'
namespace.

Next time please follow the recommendations of FAQ 5.8.

V
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May 4 '06 #2

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