Bessel Functions

• PDA_DBESJ1 (SLATEC/CAMSUN)
  Calculates the double precision Bessel function of the first kind of order one for double precision argument X.

PDA_DBESJ1 has not yet been used anywhere to replace S17AFF. Thus the migration hints given here may contain errors or may be based on misunderstandings.

The Bessel function J_1() in NAG is S17AFF. In SLATEC it is replaced by PDA_DBESJ1. The NAG code might look like

      INTEGER IFAIL
      DOUBLE PRECISION X, P
      DOUBLE PRECISION S17AFF
      IFAIL = 1
      P = S17AFF( X, IFAIL )
      IF ( IFAIL .NE. 0 ) THEN
         An error has occurred
      END IF

The new code would be

      INTEGER IFAIL
      DOUBLE PRECISION X, P
      DOUBLE PRECISION PDA_DBESJ1
      IFAIL = 0
      P = PDA_DBESJ1( X, IFAIL )
      IF ( IFAIL .NE. 0 ) THEN
         An error has occurred
      END IF