anchor.diff:  C       require up to 25 calls to ran1.
           x=0. 
           do 11 j=1,n 
  -          call random_number(rn)
  +!           call random_number(rn)
  +          rn = rand()
             if(rn.lt.p) x=x+1. 
      11   enddo 
         else if (am.lt.1.) then 
  
positive.code:         t=1.2*sq*(1.+y**2)*dexp(oldg-gammln(em+1.) 
       +-gammln(en-em+1.)+em*plog+(en-em)*pclog) 
  C       Reject. This happens about 1.5 times per deviate, on average.
          call random_number(rn)
          if (rn.gt.t) goto 2 
          x=em 
          endif 
  
negative.code:       DOUBLE PRECISION X, Y, S, ONE, TWO
        DATA ONE /1.0/, TWO /2.0/
  C
  !     1 call random_number(x)
      1 X = rand()
  !       call random_number(y)
        Y = rand()
        X = TWO * X - ONE
        Y = TWO * Y - ONE
        S = X * X + Y * Y
  