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*DECK ZABS
DOUBLE PRECISION FUNCTION ZABS (ZR, ZI)
C***BEGIN PROLOGUE ZABS
C***SUBSIDIARY
C***PURPOSE Subsidiary to ZBESH, ZBESI, ZBESJ, ZBESK, ZBESY, ZAIRY and
C ZBIRY
C***LIBRARY SLATEC
C***TYPE ALL (ZABS-A)
C***AUTHOR Amos, D. E., (SNL)
C***DESCRIPTION
C
C ZABS COMPUTES THE ABSOLUTE VALUE OR MAGNITUDE OF A DOUBLE
C PRECISION COMPLEX VARIABLE CMPLX(ZR,ZI)
C
C***SEE ALSO ZAIRY, ZBESH, ZBESI, ZBESJ, ZBESK, ZBESY, ZBIRY
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 830501 DATE WRITTEN
C 910415 Prologue converted to Version 4.0 format. (BAB)
C***END PROLOGUE ZABS
DOUBLE PRECISION ZR, ZI, U, V, Q, S
C***FIRST EXECUTABLE STATEMENT ZABS
U = ABS(ZR)
V = ABS(ZI)
S = U + V
C-----------------------------------------------------------------------
C S*1.0D0 MAKES AN UNNORMALIZED UNDERFLOW ON CDC MACHINES INTO A
C TRUE FLOATING ZERO
C-----------------------------------------------------------------------
S = S*1.0D+0
IF (S.EQ.0.0D+0) GO TO 20
IF (U.GT.V) GO TO 10
Q = U/V
ZABS = V*SQRT(1.D+0+Q*Q)
RETURN
10 Q = V/U
ZABS = U*SQRT(1.D+0+Q*Q)
RETURN
20 ZABS = 0.0D+0
RETURN
END
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