df/d63/pchst_8f_source.html

*DECK PCHST

      REAL FUNCTION pchst (ARG1, ARG2)

C***BEGIN PROLOGUE  PCHST

C***SUBSIDIARY

C***PURPOSE  PCHIP Sign-Testing Routine

C***LIBRARY   SLATEC (PCHIP)

C***TYPE      SINGLE PRECISION (PCHST-S, DPCHST-D)

C***AUTHOR  Fritsch, F. N., (LLNL)

C***DESCRIPTION

C

C         PCHST:  PCHIP Sign-Testing Routine.

C

C     Returns:

C        -1. if ARG1 and ARG2 are of opposite sign.

C         0. if either argument is zero.

C        +1. if ARG1 and ARG2 are of the same sign.

C

C     The object is to do this without multiplying ARG1*ARG2, to avoid

C     possible over/underflow problems.

C

C  Fortran intrinsics used:  SIGN.

C

C***SEE ALSO  PCHCE, PCHCI, PCHCS, PCHIM

C***ROUTINES CALLED  (NONE)

C***REVISION HISTORY  (YYMMDD)

C   811103  DATE WRITTEN

C   820805  Converted to SLATEC library version.

C   870813  Minor cosmetic changes.

C   890411  Added SAVE statements (Vers. 3.2).

C   890411  REVISION DATE from Version 3.2

C   891214  Prologue converted to Version 4.0 format.  (BAB)

C   900328  Added TYPE section.  (WRB)

C   910408  Updated AUTHOR and DATE WRITTEN sections in prologue.  (WRB)

C   930503  Improved purpose.  (FNF)

C***END PROLOGUE  PCHST

C

C**End

C

C  DECLARE ARGUMENTS.

C

      REAL  ARG1, ARG2

C

C  DECLARE LOCAL VARIABLES.

C

      REAL  ONE, ZERO

      SAVE zero, one

      DATA  zero /0./,  one /1./

C

C  PERFORM THE TEST.

C

C***FIRST EXECUTABLE STATEMENT  PCHST

      pchst = sign(one,arg1) * sign(one,arg2)

      IF ((arg1.EQ.zero) .OR. (arg2.EQ.zero))  pchst = zero

C

      RETURN

C------------- LAST LINE OF PCHST FOLLOWS ------------------------------

      END