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49 lines
1.5 KiB
Fortran
49 lines
1.5 KiB
Fortran
*DECK CBETA
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COMPLEX FUNCTION CBETA (A, B)
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C***BEGIN PROLOGUE CBETA
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C***PURPOSE Compute the complete Beta function.
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C***LIBRARY SLATEC (FNLIB)
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C***CATEGORY C7B
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C***TYPE COMPLEX (BETA-S, DBETA-D, CBETA-C)
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C***KEYWORDS COMPLETE BETA FUNCTION, FNLIB, SPECIAL FUNCTIONS
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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 CBETA computes the complete beta function of complex parameters A
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C and B.
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C Input Parameters:
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C A complex and the real part of A positive
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C B complex and the real part of B positive
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C
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C***REFERENCES (NONE)
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C***ROUTINES CALLED CGAMMA, CLBETA, GAMLIM, XERMSG
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C***REVISION HISTORY (YYMMDD)
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C 770701 DATE WRITTEN
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C 890206 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 900326 Removed duplicate information from DESCRIPTION section.
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C (WRB)
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C 900727 Added EXTERNAL statement. (WRB)
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C***END PROLOGUE CBETA
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COMPLEX A, B, CGAMMA, CLBETA
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EXTERNAL CGAMMA
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SAVE XMAX
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DATA XMAX / 0.0 /
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C***FIRST EXECUTABLE STATEMENT CBETA
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IF (XMAX.EQ.0.0) THEN
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CALL GAMLIM (XMIN, XMAXT)
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XMAX = XMAXT
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ENDIF
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C
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IF (REAL(A) .LE. 0.0 .OR. REAL(B) .LE. 0.0) CALL XERMSG ('SLATEC',
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+ 'CBETA', 'REAL PART OF BOTH ARGUMENTS MUST BE GT 0', 1, 2)
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C
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IF (REAL(A)+REAL(B).LT.XMAX) CBETA = CGAMMA(A) * (CGAMMA(B)/
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1 CGAMMA(A+B) )
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IF (REAL(A)+REAL(B).LT.XMAX) RETURN
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C
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CBETA = EXP (CLBETA(A, B))
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C
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RETURN
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END
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