f(a,b) = f(a +b)

[D J Wallace]

The function f(a,b) is translation invariant, in the sense that if you
think of a and b as coordinates on a line, its value is unchanged under
the transformation a -> a+x, b -> b-x (any x).  I don't think there is a
need to introduce any special name for this.

David Wallace

> I am looking for a name to the constraint
> 
> f(a,b) = f(a+b).
> 
> Do you have any suggestions ?
> 
> 
> Thanks
> 
> 
> Javier