std::map containing a struct of four doubles as key

[miteshpandey]

Hello all,

I have a struct of four doubles and I want to use it as a key to std::map

struct MatPropVals
{
   double ambient;
   double diffuse;
   double specular;
   double emission;
}

How do I write the comparing function. I know I have to be careful about comparing doubles. Can somebody please help me. Before this I have only use std::map with simple types.

I don't want to insert a new MatPropVals object if it has already been inserted with all the four double values being equal. std::map will take care of this. But how do I write the comparing function.

I know that there is a FAQ about comparing doubles (epsilon thing). Does it apply in my case as well. I will take care of this but just need help on the comparing function.

Thanks in advance