ln gamma

[Olivier Ramare <ramare@agat.univ-lille1.fr>]

Dear all,

  Trying to understand the code of PARI that
computes lngamma for complex argument: cxlngamma.
The trouble is that the answer has an argument
between -pi and pi and that I would rather it
to be the continuous branch that has 0 imaginary
part on the real axis.
  This code is a bit difficult to read (no comments,
variables like p1, p2 ...) and I don't even see which
formula is being used, because the initialisation of
the variables is fairly ... intricate (half of the code
if I understand well).
  Among the things I don't grasp:
   -- lines like
  "pitemp = mppi(l2); setexpo(pitemp,2); "
  "p7 = mplog(pitemp); setexpo(pitemp,1);"
  "setexpo(p7,-1); "
  What can be this setexpo-way of doing ??
   -- What about the length in this ?
  "p5=cgetg(3,t_COMPLEX);"
  "p5[1]=lgetr(l2); setlg(p5[1],4);"
  "p5[2]=lgetr(l2); setlg(p5[2],4);"
   -- who knows who is bernzone ?

  Well, any comments on this piece of code would
be appreciated, I'm fairly drowned in it :(((
  Best,
  Amities,
           Olivier