anchor.diff:  C       Purpose: Compute the associated Legendre function
   C                Pmv(x) with an integer order and an arbitrary 
   C                nonnegative degree v
  -C       Input :  x   --- Argument of Pm(x)  ( -1  x  1 )
  +C       Input :  x   --- Argument of Pm(x)  ( -1 ≤ x ≤ 1 )
   C                m   --- Order of Pmv(x)
   C                v   --- Degree of Pmv(x)
   C       Output:  PMV --- Pmv(x)
  
positive.code: C
  C       ============================================
  C       Purpose: Compute exponential integral En(x)
  C       Input :  x --- Argument of En(x) ( x  20 )
  C                n --- Order of En(x)
  C       Output:  EN(n) --- En(x)
  C       Routine called: E1XB for computing E1(x)
  
negative.code: C
  C       ===============================================================
  C       Purpose: Compute Mathieu functions cem(x,q) and sem(x,q)
  C                and their derivatives ( q ≥ 0 )
  C       Input :  KF  --- Function code
  C                        KF=1 for computing cem(x,q) and cem'(x,q)
  C                        KF=2 for computing sem(x,q) and sem'(x,q)
  