de/d5b/dpchst_8f_source.html

 *DECK DPCHST

       DOUBLE PRECISION FUNCTION dpchst (ARG1, ARG2)

 C***BEGIN PROLOGUE  DPCHST

 C***SUBSIDIARY

 C***PURPOSE  DPCHIP Sign-Testing Routine

 C***LIBRARY   SLATEC (PCHIP)

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

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

 C***DESCRIPTION

 C

 C         DPCHST:  DPCHIP Sign-Testing Routine.

 C

 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  DPCHCE, DPCHCI, DPCHCS, DPCHIM

 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   890531  Changed all specific intrinsics to generic.  (WRB)

 C   890531  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  DPCHST

 C

 C**End

 C

 C  DECLARE ARGUMENTS.

 C

       DOUBLE PRECISION  arg1, arg2

 C

 C  DECLARE LOCAL VARIABLES.

 C

       DOUBLE PRECISION  one, zero

       SAVE zero, one

       DATA  zero /0.d0/,  one/1.d0/

 C

 C  PERFORM THE TEST.

 C

 C***FIRST EXECUTABLE STATEMENT  DPCHST

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

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

 C

       RETURN

 C------------- LAST LINE OF DPCHST FOLLOWS -----------------------------

       END

dpchst
double precision function dpchst(ARG1, ARG2)
Definition: dpchst.f:3