Question

I have implemented my own container:

template<typename T>
class MyContainer
{
    // body where in some point 2 elements of collection are compared (-1, 0 and 1 possible comparison results)
};

What I want to do is add support of function objects, just like in std::set, where it is possible to do function object like this:

struct Comparator
{
    bool operator()(const char* s1, const char* s2) const
    {
        return strcmp(s1, s2) < 0;
    }
};

and then pass it as set parameter:

std::set<const char*, Comparator> SomeSet;

I'm not every-day C++ programmer, so I need help to achieve that. What must I do in order to add support to this? Must I create field in MyContainer in order to store function object in it to use it in my sorting methods inside container?

Was it helpful?

Solution

I resolved it by adding default template value, and defining default comparing class:

template<typename T, class Compare = DefaultTreeOrder<T>>
class MyContainer
{
    private:
        Compare compare;
    public:
        MyContainer()
        {
            compare = Compare();
        }
};

where DefaultTreeOrder is:

template<typename T>
class DefaultTreeOrder 
{
    public:
        int operator()(T value1, T value2)
        {
            less<T> l;
            greater<T> g;

            if(l(value1, value2))
            {
               return 1;
            }
            else if(g(value1, value2))
            {
                return -1;
            }

            return 0;
        } 
};
Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top