Subroutine MFCAPO(x,y,z,r,t,p)
c   ================================
c
c
c  Routine to convert from CArtesian to POlar coordinartes.
C  Input:  x,y,z => cartesian x,y,z
C  Output: r,t,p => radius,theta,phi
C
c
      Implicit None
c
      real x,y,z,r,t,p
      real pi,twopi,pihalf
      logical first /.true./
      save    first,pi,twopi,pihalf
c
      if(first) then
       first=.false.
       pi=acos(-1.)
       twopi=2.*pi
       pihalf=0.5*pi
      endif
      if(abs(x).lt.1.E-6) x=0.
      if(abs(y).lt.1.E-6) y=0.
      if(abs(z).lt.1.E-6) z=0.
      r=sqrt(x*x+y*y+z*z)
      if(z.ne.0.) then
       t=acos(z/r)
       if(t.lt.0) t=t+pi
      else
       t=pihalf
      endif
      if(x+y.eq.0.) then
       p=0.
      else
       p=atan2(y,x)
       if(p.lt.0) p=p+twopi
      endif
      end
c