Re: using std::find

From:

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

Newsgroups:

comp.lang.c++

Date:

Wed, 14 Mar 2007 14:20:24 -0400

Message-ID:

<et9ed9$988$1@news.datemas.de>

red floyd wrote:

Victor Bazarov wrote:

brekehan wrote:

If I have a class
MyClass
{
...bunch o data and methods
int x;
};

and a stl container of MyClass objects

Is there a way to use std::find to get all the elements whose
member x is of om value?

"om" value? What's "om" value? Sorry, English is not my mother
tongue.

All the example on the net are of a collection of some built in type
for simplicity, but do not show how to use a member of your own type
as the value being sought.

What does your favourite C++ book say? Don't you have a copy of
Josuttis' "The C++ Standard Library"? You can define your own
functor to compare the value of the 'x' member with the given value
and then call

std::find(container.begin(), container.end(), yourFunctor(42));

V

I think he wants remove_copy_if() with negated functor?

std::vector<MyClass> v;

struct hasElement: public std::unary_function<MyClass, bool>
{
   bool operator()(const MyClass& elem) const
   {
      return elem.x == x;
   }
   hasElement(int x_) : x(x_) { }
private
   int x;
};

std::remove_copy_if(container.begin(), container.end(),
                    std::back_inserter(v),
                    std::not(hasElement(42))_;

I couldn't find the word "remove" in the original post. Only "get"
and "find". For that 'find' is called in a 'while' loop and the
beginning of the range should keep changing:

    it = c.begin();
    while (true) {
        it = std::find(it, c.end(), hasElement(42));
        if (it != c.end()) {
            // do something with 'it' or with '*it' or with it->x or...
        }
        else
            break;
    }

V
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