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+*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