Ocaml fixed point implementation
Ocaml fixed point implementation
Its a little hard to understand the rationale of this problem. Not every function is going to have a fixed point. For example fun x > (x + 1) mod 5
. Not every function with a fixed point will reach the fixed point by repeated application from a distinct starting point. (I just did some googling, and fixed points like this are called attractive fixed points.)
Here are some comments:

You shouldnt use
==
, which is the physical equality operator. You possibly want to use=
, equality of values. 
However, I dont see what the
eq
parameter is for. Perhaps the caller is allowed to specify what equality to use. If so, you should use this instead of==
.