hon.f

      program hon
      integer,parameter::n=100
      real,dimension(n)::x,psi
      real f,L
      common x,psi,h
      open(10,file='hon.txt')
      L=8
      e1=0
      e2=1
      h=L/(n-1)
      do 11 i=1,n
      x(i)=-.5*L+(i-1)*h
11    continue
      do 12 i=1,100
      e=(e1+e2)/2
      if (f(e).lt.0) then
      e2=e
      else
      e1=e
      endif
      if (abs((e1-e2)/e1).lt.0.000001) goto 13
12    continue
13    write(*,*) 'Energy =',e
      do 14 i=1,n
      write(10,*) x(i),psi(i)
14    continue
      end

      function f(e)
      integer,parameter::n=100
      real,dimension(n)::x,psi,l
      common x,psi,h
      do 13 i=1,n
      l(i)=2*(e-.5*x(i)**2)
13    continue
      psi(1)=0
      psi(2)=1e-5
      do 14 i=2,n-1
      psi(i+1)=((2-5*h**2/6*l(i))*psi(i)
     & -(1+h**2/12*l(i-1))*psi(i-1))/(1+h**2/12*l(i+1))
14    continue
      f=psi(n)
      return
      end