Module dati
  real ::A,C
end Module dati


program provaFind

  USE dati

  implicit none
  real(KIND=8) :: x,FindZeroNewton
  logical :: trovato
  real(KIND=8), EXTERNAL :: miafunz,miader,miafunz1,miader1

  write(6,*)'A,C'
  read(5,*) a,c

  x=FindZeroNewton(0.3D0,.0001D0,300,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)
  USE dati

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

  miafunz=A*x**2-C
end function miafunz


real(KIND=8) function miader(x)
  USE dati

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

  miader=A*2*x
end function miader


real(KIND=8) function miafunz1(x)
  USE dati

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

  miafunz1=A*x**3-C
end function miafunz1


real(KIND=8) function miader1(x)
  USE dati

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

  miader1=3*A*x**2
end function miader1