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- *DECK CATAN2
- COMPLEX FUNCTION CATAN2 (CSN, CCS)
- C***BEGIN PROLOGUE CATAN2
- C***PURPOSE Compute the complex arc tangent in the proper quadrant.
- C***LIBRARY SLATEC (FNLIB)
- C***CATEGORY C4A
- C***TYPE COMPLEX (CATAN2-C)
- C***KEYWORDS ARC TANGENT, ELEMENTARY FUNCTIONS, FNLIB, POLAR ANGEL,
- C QUADRANT, TRIGONOMETRIC
- C***AUTHOR Fullerton, W., (LANL)
- C***DESCRIPTION
- C
- C CATAN2(CSN,CCS) calculates the complex trigonometric arc
- C tangent of the ratio CSN/CCS and returns a result whose real
- C part is in the correct quadrant (within a multiple of 2*PI). The
- C result is in units of radians and the real part is between -PI
- C and +PI.
- C
- C***REFERENCES (NONE)
- C***ROUTINES CALLED CATAN, XERMSG
- C***REVISION HISTORY (YYMMDD)
- C 770401 DATE WRITTEN
- 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 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
- C 900326 Removed duplicate information from DESCRIPTION section.
- C (WRB)
- C***END PROLOGUE CATAN2
- COMPLEX CSN, CCS, CATAN
- SAVE PI
- DATA PI / 3.1415926535 8979323846E0 /
- C***FIRST EXECUTABLE STATEMENT CATAN2
- IF (ABS(CCS).EQ.0.) GO TO 10
- C
- CATAN2 = CATAN (CSN/CCS)
- IF (REAL(CCS).LT.0.) CATAN2 = CATAN2 + PI
- IF (REAL(CATAN2).GT.PI) CATAN2 = CATAN2 - 2.0*PI
- RETURN
- C
- 10 IF (ABS(CSN) .EQ. 0.) CALL XERMSG ('SLATEC', 'CATAN2',
- + 'CALLED WITH BOTH ARGUMENTS ZERO', 1, 2)
- C
- CATAN2 = CMPLX (SIGN(0.5*PI,REAL(CSN)), 0.0)
- C
- RETURN
- END
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