anchor.diff:          NM=0
           IF (IL1) NM=ABS(A)
           IF (IL2) NM=ABS(AA)
  +C       IL1: DLMF 13.2.7 with k=-s-a
  +C       IL2: DLMF 13.2.8
           IF (IL1.OR.IL2) THEN
              HU=1.0D0
              R=1.0D0
  
positive.code:      &          .100475571822880D-01, .738993116334531D-02,
       &          .471272992695363D-02, .202681196887362D-02/
          ID=9
          A1=A-1.0D0
          B1=B-A-1.0D0
          C=12.0D0/X
  
negative.code: C       Routine called: GAMMA2 for computing gamma function
  C       ======================================================
  C
  C       DLMF 13.2.42 with prefactors rewritten according to
  C       DLMF 5.5.3, M(a, b, x) with DLMF 13.2.2
  C
          IMPLICIT DOUBLE PRECISION (A-H,O-Z)
          ID=-100
          PI=3.141592653589793D0
  