SUBROUTINE GAULEG(X1,X2,X,W,N,M)
C     ================================
C
C     set up angle points
C
      INCLUDE 'IMPLIC.FOR'
      DIMENSION X(M),W(M)
      PARAMETER (EPS=3.D-14,half=0.5d0,pi=3.141592654d0,quart=0.25,
     *            un=1.d0, two=2.d0)
c
      N2=(N+1)/2
      XM=HALF*(X2+X1)
      XL=HALF*(X2-X1)
      DO I=1,N2
         Z=COS(PI*(I-quart)/(N+half))
1        CONTINUE
         P1=1.D0
         P2=0.D0
         DO J=1,N
            P3=P2
            P2=P1
            P1=((TWO*J-UN)*Z*P2-(J-UN)*P3)/J
         END DO
         PP=N*(Z*P1-P2)/(Z*Z-un)
         Z1=Z
         Z=Z1-P1/PP
         IF(ABS(Z-Z1).GT.EPS) GO TO 1
         X(I)=XM-XL*Z
         X(N+1-I)=XM+XL*Z
         W(I)=TWO*XL/((UN-Z*Z)*PP*PP)
         W(N+1-I)=W(I)
      END DO
      RETURN
      END