title: Fortran: is 0.d0 always == 0?
body: <p>In fortran, can I always count on 0.d0 == 0 to result in .true. ?
  I.e.:</p>
  
  <pre><code>real(8) :: x
  integer :: i
  
  x = 0.d0
  i = 0
  write(*,*) x == i
  </code></pre>
  
  <p>I have tried in a simple piece of code and it turns out as .true. but can I always trust this?
  The reason for this is I want to avoid problems with <code>acos(x)</code> if x &lt; -1.</p>