Specialization of 'template struct std::less' in different namespace

Question

I am specializing the \'less\' (predicate) for a data type.

The code looks like this:

template<>
struct std::less
{
   bool          


        

Answer 1

The less functor doesn't have to be in std namespace. So

struct A
{
    A(int _v=0):v(_v){}
    int v;
};


template<>  struct less
{
    bool operator()(const A& k1, const A& k2) const
    {
        return k1.v < k2.v;
    }
};


std::map m;
m[A(1)] = 1;
m[A(2)] = 2;

Works as expected. (Calls the functor you just created).

I guess you already know, but you can just write your own operator<(k1,k2), which is what default less functor looks for.

bool operator<(const DateTimeKey & k1, const DateTimeKey & k2)
{
//your code...
}