C
C     ..................................................................
C
C        SUBROUTINE DQA4
C
C        PURPOSE
C           TO COMPUTE INTEGRAL(EXP(-X)*FCT(X)/SQRT(X), SUMMED OVER X
C                               FROM 0 TO INFINITY).
C
C        USAGE
C           CALL DQA4 (FCT,Y)
C           PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
C
C        DESCRIPTION OF PARAMETERS
C           FCT    - THE NAME OF AN EXTERNAL DOUBLE PRECISION FUNCTION
C                    SUBPROGRAM USED.
C           Y      - THE RESULTING DOUBLE PRECISION INTEGRAL VALUE.
C
C        REMARKS
C           NONE
C
C        SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C           THE EXTERNAL DOUBLE PRECISION FUNCTION SUBPROGRAM FCT(X)
C           MUST BE FURNISHED BY THE USER.
C
C        METHOD
C           EVALUATION IS DONE BY MEANS OF 4-POINT GENERALIZED GAUSS-
C           LAGUERRE QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY
C           WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 7.
C           FOR REFERENCE, SEE
C           SHAO/CHEN/FRANK, TABLES OF ZEROS AND GAUSSIAN WEIGHTS OF
C           CERTAIN ASSOCIATED LAGUERRE POLYNOMIALS AND THE RELATED
C           GENERALIZED HERMITE POLYNOMIALS, IBM TECHNICAL REPORT
C           TR00.1100 (MARCH 1964), PP.15-16.
C
C     ..................................................................
C
      SUBROUTINE DQA4(FCT,Y)
C
C
      DOUBLE PRECISION X,Y,FCT
C
      X=.8588635689012034D1
      Y=.39920814442273524D-3*FCT(X)
      X=.39269635013582872D1
      Y=Y+.34155966014826951D-1*FCT(X)
      X=.13390972881263614D1
      Y=Y+.41560465162978376D0*FCT(X)
      X=.14530352150331709D0
      Y=Y+.13222940251164826D1*FCT(X)
      RETURN
      END
