How can I use a custom type as key for a map in C++?

Question

I am trying to assign a custom type as a key for std::map. Here is the type which I am using as key:

struct Foo
{
    Foo(std::string s) : foo_va         


        

Answer 1

It's probably looking for const member operators (whatever the correct name is). This works (note const):

bool operator<(const Foo& foo1) const { return foo_value < foo1.foo_value;}

EDIT: deleted operator> from my answer as it was not needed (copy/paste from question) but it was attracting comments :)

Note: I'm 100% sure that you need that const because I compiled the example.