anchor.diff:                IF (K.LE.N) CBJ(K)=CF
                 CF2=CF1
   75            CF1=CF
  -           IF (CDABS(CJV0).GT.CDABS(CJV1)) CS=CJV0/CF
  -           IF (CDABS(CJV0).LE.CDABS(CJV1)) CS=CJV1/CF2
  +           IF (ABS(CJV0).GT.ABS(CJV1)) CS=CJV0/CF
  +           IF (ABS(CJV0).LE.ABS(CJV1)) CS=CJV1/CF2
              DO 80 K=0,N
   80            CBJ(K)=CS*CBJ(K)
           ENDIF
  
positive.code:         EL=0.5772156649015329D0
          RP2=2.0D0/PI
          CI=(0.0D0,1.0D0)
          A0=CDABS(Z)
          Z2=Z*Z
          Z1=Z
          IF (A0.EQ.0.0D0) THEN
  
negative.code:            DO 10 K=1,500
                CR=-CR*K*Z/(K+1.0D0)**2
                CE1=CE1+CR
                IF (ABS(CR).LE.ABS(CE1)*1.0D-15) GO TO 15
  10         CONTINUE
  15         CONTINUE
             IF (X.LE.0.0.AND.DIMAG(Z).EQ.0.0) THEN
  C     Careful on the branch cut -- use the sign of the imaginary part
  C     to get the right sign on the factor if pi.
                CE1=-EL-LOG(-Z)+Z*CE1-DSIGN(PI,DIMAG(Z))*(0.0D0,1.0D0)
             ELSE
                CE1=-EL-LOG(Z)+Z*CE1
             ENDIF
          ELSE
  C          Continued fraction https://dlmf.nist.gov/6.9
  