Re: map with pair as key

From:

"Peter" <peterf@xpedion.com>

Newsgroups:

comp.lang.c++

Date:

20 Jun 2006 14:34:14 -0700

Message-ID:

<1150839254.266148.102850@u72g2000cwu.googlegroups.com>

kietzi@web.de wrote:

Hello world,
I was wondering whether it would be possible to create a map which uses
a pair of ints as key and a float as value. I have used maps with const

a pair provides all the required operators so this is fine.

char*[] as key, but have so far not been successful to use a version

a map with char ** as the key?
char ** does not provide any operators thus your code would not
compile.

which uses pairs as keys.

For instance, I would like to set up the map as follows:

struct eqstr {
    bool operator()(pair<int,int> s1, pair<int,int> s2) const{
        return ((s1.first==s2.first) && (s1.second==s2.second));
    }
};

this operator is provided by pair so you don't need to provide it.

std::map<std::pair<int,int>*, float, hash<const char*>, eqstr>
connections;

a map using a pointer to a pair as key?
This code does not compile.
What is the problem with:

std::map<std::pair<int, int>, float>

Unforunately, this does not work. How would I put elements into the map
and how could I access them? Where could be the problem with the eqstr
struct and map-initialization?

Thanks a lot you guys...

Tim