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- SUBROUTINE ZLOG(AR, AI, BR, BI, IERR)
- C***BEGIN PROLOGUE ZLOG
- C***REFER TO ZBESH,ZBESI,ZBESJ,ZBESK,ZBESY,ZAIRY,ZBIRY
- C
- C DOUBLE PRECISION COMPLEX LOGARITHM B=CLOG(A)
- C IERR=0,NORMAL RETURN IERR=1, Z=CMPLX(0.0,0.0)
- C***ROUTINES CALLED ZABS
- C***END PROLOGUE ZLOG
- DOUBLE PRECISION AR, AI, BR, BI, ZM, DTHETA, DPI, DHPI
- DOUBLE PRECISION ZABS
- DATA DPI , DHPI / 3.141592653589793238462643383D+0,
- 1 1.570796326794896619231321696D+0/
- C
- IERR=0
- IF (AR.EQ.0.0D+0) GO TO 10
- IF (AI.EQ.0.0D+0) GO TO 20
- DTHETA = DATAN(AI/AR)
- IF (DTHETA.LE.0.0D+0) GO TO 40
- IF (AR.LT.0.0D+0) DTHETA = DTHETA - DPI
- GO TO 50
- 10 IF (AI.EQ.0.0D+0) GO TO 60
- BI = DHPI
- BR = DLOG(DABS(AI))
- IF (AI.LT.0.0D+0) BI = -BI
- RETURN
- 20 IF (AR.GT.0.0D+0) GO TO 30
- BR = DLOG(DABS(AR))
- BI = DPI
- RETURN
- 30 BR = DLOG(AR)
- BI = 0.0D+0
- RETURN
- 40 IF (AR.LT.0.0D+0) DTHETA = DTHETA + DPI
- 50 ZM = ZABS(COMPLEX(AR,AI))
- BR = DLOG(ZM)
- BI = DTHETA
- RETURN
- 60 CONTINUE
- IERR=1
- RETURN
- END
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