[Proj] Fastest way to compare projetion definitions

[Calogero Mauceri]

Hi,

I need to compare two projections definitions say

projPJ p1 and projPJ p2

in order to compare them I'm currently getting their pro4 string 
definition, using pj_get_def, and comparing the two proj4 strings.
I wonder if there is a faster way to compare them.
I noticed there is an undocumented pj_compare_datums function in 
proj_api.h, but I'm not sure it can be used for that purpose.

Thanks,
     Calogero