[Help-gsl] using own (non-GSL random number generator with randist.h)

[m g william]

I'd like my own rng to 'power' distributions from randist.h but don't know what 
form it should take to be accepted by the standard procedure to get them into 
the distrbutions
ie
.
.
gsl_rng_type * T = myOwnRng
r = gsl_rng_alloc(T)
num = someDist(r, etc..) 

Could someone please point me to the minimum spec my rng should conform to.

I would like it to be a c++ class with different instantiations representing 
different generator instances. 

a very simple working example would be the ultimate, but any advice would be 
much appreciated.