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decus/20-0026/qa5.doc
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SUBROUTINE QA5
PURPOSE
TO COMPUTE INTEGRAL(EXP(-X)*FCT(X)/SQRT(X), SUMMED OVER X
FROM 0 TO INFINITY).
USAGE
CALL QA5 (FCT,Y)
PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
DESCRIPTION OF PARAMETERS
FCT - THE NAME OF AN EXTERNAL FUNCTION SUBPROGRAM USED.
Y - THE RESULTING INTEGRAL VALUE.
REMARKS
NONE
SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
THE EXTERNAL FUNCTION SUBPROGRAM FCT(X) MUST BE FURNISHED
BY THE USER.
METHOD
EVALUATION IS DONE BY MEANS OF 5-POINT GENERALIZED GAUSSIAN-
LAGUERRE QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY,
WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 9.
FOR REFERENCE, SEE
CONCUS/CASSATT/JAEHNIG/MELBY, TABLES FOR THE EVALUATION OF
INTEGRAL(X**BETA*EXP(-X)*F(X), SUMMED OVER X FROM 0 TO
INFINITY) BY GAUSS-LAGUERRE QUADRATURE, MTAC, VOL.17,
ISS.83 (1963), PP.245-256.