Kurt Ewald asked:

Is there a function in GAP that calculates such a presentation of any group
G ?

IsomorphismFpGroup computes an isomorphism, the `Range' of such an isomorphism
is a finitely opresented group, `RelatorsOfFpGroup' of this gives a set of
defining relators.

Caveat: The presenytation returned is often not as nice as it could be if one workjs by hand.

Best wishes,

Alexander Hulpke

-- Colorado State University, Department of Mathematics,
Weber Building, Fort Collins, CO 80523, USA
email: hulpke@math.colostate.edu