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30 lines
866 B
FortranFixed
30 lines
866 B
FortranFixed
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DOUBLE PRECISION FUNCTION ZABS(ZR, ZI)
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C***BEGIN PROLOGUE ZABS
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C***REFER TO ZBESH,ZBESI,ZBESJ,ZBESK,ZBESY,ZAIRY,ZBIRY
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C
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C ZABS COMPUTES THE ABSOLUTE VALUE OR MAGNITUDE OF A DOUBLE
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C PRECISION COMPLEX VARIABLE CMPLX(ZR,ZI)
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C
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C***ROUTINES CALLED (NONE)
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C***END PROLOGUE ZABS
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DOUBLE PRECISION ZR, ZI, U, V, Q, S
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U = DABS(ZR)
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V = DABS(ZI)
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S = U + V
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C-----------------------------------------------------------------------
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C S*1.0D0 MAKES AN UNNORMALIZED UNDERFLOW ON CDC MACHINES INTO A
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C TRUE FLOATING ZERO
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C-----------------------------------------------------------------------
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S = S*1.0D+0
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IF (S.EQ.0.0D+0) GO TO 20
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IF (U.GT.V) GO TO 10
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Q = U/V
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ZABS = V*DSQRT(1.D+0+Q*Q)
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RETURN
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10 Q = V/U
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ZABS = U*DSQRT(1.D+0+Q*Q)
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RETURN
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20 ZABS = 0.0D+0
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RETURN
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END
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