dpchst.f
DOUBLE PRECISION FUNCTION DPCHST (ARG1, ARG2)
C***BEGIN PROLOGUE DPCHST
....
....
Warning: this routine is not intended to be user-callable.
....
....
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