Question

I’m trying to create a map whose key and value are both structs (stE and stR), so I have something like this:

 struct stR{
  char* est;
  char* et;     
 };

struct stE{
      int num;
      char* form; 
      char* et; 
      map<stE,stR> s; 
}; 

But when I want to insert a new element:

stE e;
e.num=1;
e.form="a";
e.et="b";

stE f;
f.num=2;
f.form="c";
f.et="d";

stR r;
r.est="e";
r.et="";

e.s.insert(make_pair(f, r));

It gives me an error:

C:\Dev-Cpp\include\c++\3.4.2\bits\stl_function.h In member function `bool std::less<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = stEstado]’:

I can’t find what’s the problem. Could anyone help me?
Thanks in advance.

Answer 1

When using a map, you need to provide a less-than operator or give it a comparer since it orders the keys automatically.

bool stE::operator< (const stE &);