I have a question using less function. What kind of methods, and how, do
you have to define for your class, to use it with less-function???
Shouldn.t "operator<" be enough?

I made my own class "ioValues", and want to use that in map container. So I
have to be able to sort my class' objects. So, I try to use my class with
less, but it doesn't work.
Here's what I have:

class ioValues{
  public:
        ioValues();
        ioValues(const ioValues&);
        bool operator==( const ioValues& ) const;
        ioValues &operator=( const ioValues& );
        bool operator<( const ioValues& );
.....
}

and those methods work just fine
and when I try to make my "own less" in main program:

#include <functional>
#include <map>
#include "ioValues.h"
typedef less<ioValues> _myless;
.....

when I try to compile, I get:

/opt/share/gnu/lib/g++-include/function.h: In method `bool
less<ioValues>::operator ()(const class ioValues &, const class ioValues &)
const':
/opt/share/gnu/lib/g++-include/function.h:112: no match for `operator
<(class ioValues, class ioValues)'

 Sami, raatikai@lut.fi
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Sami wrote:
 >
 > I have a question using less function. What kind of methods, and how, do
 > you have to define for your class, to use it with less-function???
 > Shouldn.t "operator<" be enough?
 >
 > I made my own class "ioValues", and want to use that in map container. So I
 > have to be able to sort my class' objects. So, I try to use my class with
 > less, but it doesn't work.
 > Here's what I have:
 >
 > class ioValues{
 >   public:
 >         ioValues();
 >         ioValues(const ioValues&);
 >         bool operator==( const ioValues& ) const;
 >         ioValues &operator=( const ioValues& );
 >         bool operator<( const ioValues& );
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This should be a const-method:
          bool operator<(const ioValues& ) const;

 > .....
 > }
 >
 > and those methods work just fine
 > and when I try to make my "own less" in main program:
 >
 > #include <functional>
 > #include <map>
 > #include "ioValues.h"
 > typedef less<ioValues> _myless;
 > .....
 >
 > when I try to compile, I get:
 >
 > /opt/share/gnu/lib/g++-include/function.h: In method `bool
 > less<ioValues>::operator ()(const class ioValues &, const class ioValues &)
 > const':
 > /opt/share/gnu/lib/g++-include/function.h:112: no match for `operator
 > <(class ioValues, class ioValues)'

--
Konstantin Baumann                   Westfaelische Wilhelms-Universitaet
Institut fuer Informatik (Zi. 603),  Einsteinstr. 62,   D-48149 Muenster
mailto:kostab@math.uni-muenster.de                  Tel:+49-251-83-32701
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