[FOM] Computing the Modulus of Continuity

[Jacques Carette]

I am looking for references on *computing* the modulus of continuity of 
explicit functions (real valued functions of a real variable).  As 
having a computable modulus of continuity is crucial for certain notions 
of functions being computable, I would expect that  people on FOM might 
be aware of such work.  My searches up to now have yielded very little 
outside a couple of examples (ie no algorithms or effective theory).

I was not able to find even simple theorems like, how does the modulus 
of continuity of f+g, f*g depend on that of f and g.  I could certainly 
go and try to derive such theorems myself, but if there are 
not-too-obscure reference works where these are already contained, I 
might as well look those up first.

Thanks for any pointers,
Jacques