Re: How are objects inserted into a set?

desktop <>
Thu, 07 Jun 2007 20:41:29 +0200
Victor Bazarov wrote:

desktop wrote:

I have implemented a red-black tree which is used for std::set.

In the C++ standard 3 different insert methods are specified for the
associative container. But as i see it insert adds an object to the
set based on a key. But where does the key come from?

It's the same as the value. Doesn't the book you're reading about
'std::set' tell you that?

If I make my own object I don't specify any unique key that insert
uses to place the object.

You do. By supplying an object with a value.

Does the insert call generate some unique key that it uses each time
an object is inserted?



It seems that I don't understand set. Inserting into a vector works fine:

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

int main() {
    std::vector<test> hh;
    test t1;
    hh.push_back(t1); // Works fine

    std::set<test> my_set;
    const test& tref = t1; // see *
    my_set.insert(tref); // fails with error: no match for
                    ?operator<? in ?__x < __y?


Can I only insert into std::set if my class 'test' define '<' and
properly some of the other operators?

I still don't see how insert gets the key from 'test' so it can put it
the right place in the tree.

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