are there any functions for computing a square root of a modulo p (prime)?

[Torbjorn Granlund]

Zimmermann Paul <Paul.Zimmermann at inria.fr> writes:

  indeed, see http://en.wikipedia.org/wiki/Tonelli%E2%80%93Shanks_algorithm.
  The Tonelli–Shanks algorithm is so useful in many applications, that it
  would make sense to have it implemented in GMP.
  
I and Niels wrote some Tonelli-Shanks code last autumn, and I suppose it
would make sense to adapt it for GMP inclusion.

-- 
Torbjörn