Function Composition: Simplifying f((f(t)-f(s))?

[Screwdriver]

Homework Statement

If f is some function defined at points "s" and "t," is there any way to simplify the following expression?

f((f(t)-f(s))

Homework Equations

None that I know of.

The Attempt at a Solution

I've been tinkering with this for a while and so far, I've determined the answer to be no. I know that

f(t)-f(s)\neq f(t-s)

in general, and that implies that

f(f(t)-f(s))\neq f(f(t))-f(f(s))

But does anyone know another way to simplify this to maybe some kind of composition?

 

[hunt_mat]

Let f(x)=sin x to give you a few ideas, I think the general answer is no.

 

[Screwdriver]

sin(sin(t)-sin(s)) = [sin\circ sin(t)][cos\circ sin(s)] - [sin\circ sin(s)][cos\circ sin(t)]

Well that's a mess and a half. It is as I feared