PROGRAM xbrent
C     driver for routine brent
      REAL EQL,TOL
      PARAMETER(TOL=1.0E-6,EQL=1.E-4)
      INTEGER i,iflag,j,nmin
      REAL amin(20),ax,b,bx,cx,fa,fb,fc,xmin
      REAL bessj0,bessj1,brent,func
      EXTERNAL func
      nmin=0
      write(*,'(/1x,a)') 'Minima of the function BESSJ0'
      write(*,'(/1x,t6,a,t19,a,t28,a,t40,a/)') 'Min. #','X',
     *     'BESSJ0(X)','BESSJ1(X)'
      do 12 i=1,100
        ax=i
        bx=i+1.0
        call mnbrak(ax,bx,cx,fa,fb,fc,func)
        b=brent(ax,bx,cx,func,TOL,xmin)
        if (nmin.eq.0) then
          amin(1)=xmin
          nmin=1
          write(*,'(1x,5x,i2,3x,3f12.6)') nmin,xmin,
     *         bessj0(xmin),bessj1(xmin)
        else
          iflag=0
          do 11 j=1,nmin
            if (abs(xmin-amin(j)).le.EQL*xmin)
     *           iflag=1
11        continue
          if (iflag.eq.0) then
            nmin=nmin+1
            amin(nmin)=xmin
            write(*,'(1x,5x,i2,3x,3f12.6)') nmin,
     *           xmin,bessj0(xmin),bessj1(xmin)
          endif
        endif
12    continue
      END

      REAL FUNCTION func(x)
      REAL bessj0,x
      func=bessj0(x)
      return
      END