program provaFind

  implicit none
  real(KIND=8) :: x,FindZeroNewton,xt,eps
  logical :: trovato
  real(KIND=8), EXTERNAL :: miafunz,miader,miafunz1,miader1
  integer:: maxp
  
  maxp=200
  eps=.00001
  xt=0.3
  
  x=FindZeroNewton(xt,eps,maxp,trovato,miafunz,miader)


  if(trovato)then
     write(6,*)'Prima Funzione X=',x
  else
     write(6,*)'Non converge'
  endif

  x=FindZeroNewton(0.3D0,.0001D0,300,trovato,miafunz1,miader1)
  if(trovato)then
     write(6,*)'Seconda Funzione X=',x
  else
     write(6,*)'Non converge'
  endif
  
end program ProvaFind

real(KIND=8)  function FindZeroNewton(xtt,eps,maxp,trovato,f,f1)
  implicit none
  real(KIND=8), INTENT(in) :: xtt,eps
  integer, INTENT(in) :: maxp
  logical, Intent(OUT) ::trovato
  real(KIND=8), EXTERNAL :: f,f1

  real(KIND=8) ::xc,xt
  integer ::i

  xt=xtt
  do i=1,maxp
     xc=xt-f(xt)/f1(xt)
     if(abs(xc-xt) < eps ) exit
     xt=xc
  enddo

  trovato= i <= maxp

  FindZeroNewton=xc
end function FindZeroNewton

real(KIND=8) function miafunz(x)
implicit none
real(KIND=8) , INTENT(IN) ::x

  miafunz=x**2-1
end function miafunz

real(KIND=8) function miader(x)
implicit none
real(KIND=8) , INTENT(IN) ::x

  miader=2*x
end function miader

real(KIND=8) function miafunz1(x)
implicit none
real(KIND=8) , INTENT(IN) ::x

  miafunz1=5*x**3-10
end function miafunz1

real(KIND=8) function miader1(x)
implicit none
real(KIND=8) , INTENT(IN) ::x

  miader1=15*x**2
end function