Re: How are objects inserted into a set?

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Fri, 8 Jun 2007 07:55:05 -0400

Message-ID:

<f4bg2s$in0$1@news.datemas.de>

Johs wrote:

[..]
I can see operators that must be defined for std::set in 23.3.3, but I
can't find any requirements for the objects that I would like to
insert. This is my object that I would like to insert into a std::set:

class test {
public:
int getpp(){return pp;}
void setpp(int i){pp = i;}

int operator<(int a) const
{
return 22;
}

private:
int pp;
};

But I still get the error:

error: no match for ?operator<? in ?__x < __y

where can I find an interface for the objects to insert?

You are supposed to implement a comparison between two objects of the
type you're going to store, not between an object and an int:

    ...
    bool operator <(test const& t) const {
        ...
    }

and the actual implementation is supposed to adhere to "strict weak
ordering" rules: if two objects ('a', 'b') are equivalent (for the
purporses of storing in that set), then 'a < b' and 'b < a' should
both return false.

V
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