C$TEST QGSM
C TO RUN AS A MAIN PROGRAM REMOVE NEXT LINE
      SUBROUTINE QGSM
C***********************************************************************
C
C  EXAMPLE OF USE OF THE PORT PROGRAM GQEXA
C
C***********************************************************************
      REAL X(5),W(5),FEXA,CALC,TRUE,PI,ERR
C
      CALL  GQEXA(5,-0.5E0,X,W)
      IWRITE=I1MACH(2)
      WRITE(IWRITE,1)
      DO 10 J=1,5
   10    WRITE(IWRITE,2) J, X(J),W(J)
      CALC = 0.E0
      DO 20 J=1,5
   20    CALC = CALC+W(J)*FEXA(X(J))
      PI   = 2.E0*ATAN2(1.E0,0.E0)
      TRUE = 0.5E0*SQRT(PI)*(1.E0-1.E0/SQRT(3.E0))
      ERR  = TRUE-CALC
      WRITE(IWRITE,3) TRUE,CALC,ERR
      STOP
    1 FORMAT(///15H TEST OF  GQEXA//30H0ABSCISSAS AND WEIGHTS FOR N=5)
    2 FORMAT(I4,0P2E16.7)
    3 FORMAT(15H0SAMPLE PROBLEM/6H TRUE=,1PE16.7/
     X   6H CALC=,1PE16.7/6H ERR =,1PE11.2)
      END
      REAL FUNCTION FEXA(X)
      REAL X
      FEXA=0.5E0*(1.E0-EXP(-2.E0*X))
      RETURN
      END

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