Sub GAULEG(X1, X2, X(), W(), N)
    EPS = 0.00000000000003
    M = (N + 1) / 2
    XM = 0.5 * (X2 + X1)
    XL = 0.5 * (X2 - X1)
    For I = 1 To M
        Z = Cos(3.141592654 * (I - 0.25) / (N + 0.5))
1       P1 = 1#
        P2 = 0#
        For J = 1 To N
            P3 = P2
            P2 = P1
            P1 = ((2# * J - 1#) * Z * P2 - (J - 1#) * P3) / J
        Next J
        PP = N * (Z * P1 - P2) / (Z * Z - 1#)
        Z1 = Z
        Z = Z1 - P1 / PP
        If Abs(Z - Z1) > EPS Then GoTo 1
        X(I) = XM - XL * Z
        X(N + 1 - I) = XM + XL * Z
        W(I) = 2# * XL / ((1# - Z * Z) * PP * PP)
        W(N + 1 - I) = W(I)
    Next I
End Sub