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50 lines
1.4 KiB
Fortran
50 lines
1.4 KiB
Fortran
*DECK CTAN
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COMPLEX FUNCTION CTAN (Z)
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C***BEGIN PROLOGUE CTAN
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C***PURPOSE Compute the complex tangent.
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C***LIBRARY SLATEC (FNLIB)
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C***CATEGORY C4A
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C***TYPE COMPLEX (CTAN-C)
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C***KEYWORDS ELEMENTARY FUNCTIONS, FNLIB, TANGENT, TRIGONOMETRIC
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C***AUTHOR Fullerton, W., (LANL)
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C***DESCRIPTION
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C
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C CTAN(Z) calculates the complex trigonometric tangent of complex
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C argument Z. Z is in units of radians.
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C
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C***REFERENCES (NONE)
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C***ROUTINES CALLED R1MACH, XERCLR, XERMSG
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C***REVISION HISTORY (YYMMDD)
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C 770401 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 890531 REVISION DATE from Version 3.2
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
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C***END PROLOGUE CTAN
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COMPLEX Z
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SAVE SQEPS
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DATA SQEPS /0./
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C***FIRST EXECUTABLE STATEMENT CTAN
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IF (SQEPS.EQ.0.) SQEPS = SQRT (R1MACH(4))
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C
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X2 = 2.0*REAL(Z)
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Y2 = 2.0*AIMAG(Z)
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C
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SN2X = SIN (X2)
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CALL XERCLR
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C
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DEN = COS(X2) + COSH(Y2)
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IF (DEN .EQ. 0.) CALL XERMSG ('SLATEC', 'CTAN',
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+ 'TAN IS SINGULAR FOR INPUT Z (X IS PI/2 OR 3*PI/2 AND Y IS 0)',
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+ 2, 2)
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C
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IF (ABS(DEN).GT.MAX(ABS(X2),1.)*SQEPS) GO TO 10
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CALL XERCLR
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CALL XERMSG ('SLATEC', 'CTAN',
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+ 'ANSWER LT HALF PRECISION, ABS(X) TOO BIG OR X TOO NEAR ' //
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+ 'PI/2 OR 3*PI/2', 1, 1)
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C
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10 CTAN = CMPLX (SN2X/DEN, SINH(Y2)/DEN)
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C
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RETURN
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END
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