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QL9.FOR
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1985-11-29
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58 lines
C
C ..................................................................
C
C SUBROUTINE QL9
C
C PURPOSE
C TO COMPUTE INTEGRAL(EXP(-X)*FCT(X), SUMMED OVER X FROM 0
C TO INFINITY).
C
C USAGE
C CALL QL9 (FCT,Y)
C PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
C
C DESCRIPTION OF PARAMETERS
C FCT - THE NAME OF AN EXTERNAL FUNCTION SUBPROGRAM USED.
C Y - THE RESULTING INTEGRAL VALUE.
C
C REMARKS
C NONE
C
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C THE EXTERNAL FUNCTION SUBPROGRAM FCT(X) MUST BE FURNISHED
C BY THE USER.
C
C METHOD
C EVALUATION IS DONE BY MEANS OF 9-POINT GAUSSIAN-LAGUERRE
C QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY WHENEVER
C FCT(X) IS A POLYNOMIAL UP TO DEGREE 17.
C FOR REFERENCE, SEE
C V.I.KRYLOV, APPROXIMATE CALCULATION OF INTEGRALS,
C MACMILLAN, NEW YORK/LONDON, 1962, PP.130-132 AND 347-352.
C
C ..................................................................
C
SUBROUTINE QL9(FCT,Y)
C
C
X=26.37407
Y=.3290874E-10*FCT(X)
X=18.83360
Y=Y+.4110769E-7*FCT(X)
X=13.46624
Y=Y+.6592123E-5*FCT(X)
X=9.372985
Y=Y+.3052498E-3*FCT(X)
X=6.204957
Y=Y+.005599627*FCT(X)
X=3.783474
Y=Y+.04746056*FCT(X)
X=2.005135
Y=Y+.1992875*FCT(X)
X=.8072200
Y=Y+.4112140*FCT(X)
X=.1523222
Y=Y+.3361264*FCT(X)
RETURN
END