relibc_openlibm/slatec/cuchk.f

*DECK CUCHK
      SUBROUTINE CUCHK (Y, NZ, ASCLE, TOL)
C***BEGIN PROLOGUE  CUCHK
C***SUBSIDIARY
C***PURPOSE  Subsidiary to SERI, CUOIK, CUNK1, CUNK2, CUNI1, CUNI2 and
C            CKSCL
C***LIBRARY   SLATEC
C***TYPE      ALL (CUCHK-A, ZUCHK-A)
C***AUTHOR  Amos, D. E., (SNL)
C***DESCRIPTION
C
C      Y ENTERS AS A SCALED QUANTITY WHOSE MAGNITUDE IS GREATER THAN
C      EXP(-ALIM)=ASCLE=1.0E+3*R1MACH(1)/TOL. THE TEST IS MADE TO SEE
C      IF THE MAGNITUDE OF THE REAL OR IMAGINARY PART WOULD UNDER FLOW
C      WHEN Y IS SCALED (BY TOL) TO ITS PROPER VALUE. Y IS ACCEPTED
C      IF THE UNDERFLOW IS AT LEAST ONE PRECISION BELOW THE MAGNITUDE
C      OF THE LARGEST COMPONENT; OTHERWISE THE PHASE ANGLE DOES NOT HAVE
C      ABSOLUTE ACCURACY AND AN UNDERFLOW IS ASSUMED.
C
C***SEE ALSO  CKSCL, CUNI1, CUNI2, CUNK1, CUNK2, CUOIK, SERI
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   ??????  DATE WRITTEN
C   910415  Prologue converted to Version 4.0 format.  (BAB)
C***END PROLOGUE  CUCHK
C
      COMPLEX Y
      REAL ASCLE, SS, ST, TOL, YR, YI
      INTEGER NZ
C***FIRST EXECUTABLE STATEMENT  CUCHK
      NZ = 0
      YR = REAL(Y)
      YI = AIMAG(Y)
      YR = ABS(YR)
      YI = ABS(YI)
      ST = MIN(YR,YI)
      IF (ST.GT.ASCLE) RETURN
      SS = MAX(YR,YI)
      ST=ST/TOL
      IF (SS.LT.ST) NZ = 1
      RETURN
      END