No match for operator<

[Laurense]

I'm using a map and, at the time of compilation, I get this error:

no match for ?operator<? in ?__x < __y?
line 230, external location: /usr/include/c++/4.4/bits/stl_function.h

I am using g++ under Linux. My map is declared as follows:

map<MyEvent, void(*)()> nameMap;

I need to combine a function (returning void) to a certain event. When this event is raised, the associated function is called.

Can someone help me why and what is the error message refers to?

[void]

Did you tried entering this in the code?

#include <map>
using namespace std;

And is MyEvent is defined somewhere? Maybe it's better if it carries a few lines of code in more

I thus established:

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

int main ()
{

map<int, void(*)()> nameMap;

return 0;
}

So surely the problem is the definition of MyEvent

[Laurense]

Originally Posted by void

Did you tried entering this in the code?

#include <map>
using namespace std;

And is MyEvent is defined somewhere? Maybe it's better if it carries a few lines of code in more

MyEvent is taken from an external library. And, of course, I imported the header <map> and the declaration use std::map<...>.

Is there anyone else with an idea?

[Zecho]

The reason for not working and 'written in the error message: no operator <for the type key (ie MyEvent), which serves to map to distinguish different elements (or rather sort tree).

Once deployed, the operator error should disappear. Alternatively you can use a different name, and pass it as the third argument of the template of map <>

[Laurense]

Originally Posted by Zecho

The reason for not working and 'written in the error message: no operator <for the type key (ie MyEvent), which serves to map to distinguish different elements (or rather sort tree).

Unfortunately I can not change MyEvent, as it is part of a library of third parties.

Originally Posted by Zecho

Once deployed, the operator error should disappear. Alternatively you can use a different name, and pass it as the third argument of the template of map <>

What do you mean by a "different name"?

[Zecho]

You can implement it without touching the class as a function

bool operator < ( const MyEvent& x, const MyEvent& y );

What do you mean by a "different name"?

By that I mean you must use a function object:

struct compare
{
    bool operator ()( const MyEvent& x, const MyEvent& y )
    {
        return ???;
    }
};


int main()
{
    map<MyEvent,bool,compare> myMap;

    ...
}