Function: ideallog
Section: number_fields
C-Name: zideallog
Prototype: GGG
Help: ideallog(nf,x,bid): if bid is a big ideal, as given by
 idealstar(nf,I,1) or idealstar(nf,I,2), gives the vector of exponents on the
 generators bid[2][3] (even if these generators have not been computed)

