QCaml/common/constants.org

#+begin_src elisp tangle: no :results none :exports none
(setq pwd (file-name-directory buffer-file-name))
(setq name (file-name-nondirectory (substring buffer-file-name 0 -4)))
(setq lib (concat pwd "lib/"))
(setq testdir (concat pwd "test/"))
(setq mli (concat lib name ".mli"))
(setq ml  (concat lib name ".ml"))
(setq test-ml  (concat testdir name ".ml"))
(org-babel-tangle)
#+end_src 

* Constants
  :PROPERTIES:
  :header-args: :noweb yes :comments both
  :END:

  All constants used in the program.
  
** Thresholds

   #+begin_src ocaml :tangle (eval mli)
val epsilon          : float
val integrals_cutoff : float
   #+end_src

   | ~epsilon~          | Value below which a float is considered null. Default is \epsilon = 2.10^{-15} |
   | ~integrals_cutoff~ | Cutoff value for integrals. Default is \epsilon                                |

   #+begin_src ocaml :tangle (eval ml) :exports none
let epsilon = 2.e-15
let integrals_cutoff = epsilon
   #+end_src

** Mathematical constants 

   #+begin_src ocaml :tangle (eval mli)
val pi             : float
val two_pi         : float
val sq_pi          : float
val sq_pi_over_two : float
val pi_inv         : float
val two_over_sq_pi : float
   #+end_src

   | ~pi~             | $\pi = 3.141~592~653~589~793~12$ |
   | ~two_pi~         | $2 \pi$                          |
   | ~sq_pi~          | $\sqrt{\pi}$                     |
   | ~sq_pi_over_two~ | $\sqrt{\pi} / 2$                 |
   | ~pi_inv~         | $1 / \pi$                        |
   | ~two_over_sq_pi~ | $2 / \sqrt{\pi}$                 |
    
   #+begin_src ocaml :tangle (eval ml) :exports none
let pi             = acos (-1.)
let two_pi         = 2. *. pi
let sq_pi          = sqrt pi
let sq_pi_over_two = sq_pi *. 0.5
let pi_inv         = 1. /. pi
let two_over_sq_pi = 2. /. sq_pi
   #+end_src

** Physical constants
   
   #+begin_src ocaml :tangle (eval mli)
val a0       : float
val a0_inv   : float
val ha_to_ev : float
val ev_to_ha : float
   #+end_src

   | ~a0~       | Bohr's radius : $a_0 = 0.529~177~210~67(23)$ angstrom |
   | ~a0_inv~   | $1 / a_0$                                             |
   | ~ha_to_ev~ | Hartree to eV conversion factor : $27.211~386~02(17)$ |
   | ~ev_to_ha~ | eV to Hartree conversion factor : 1 / ~ha_to_ev~      |
    
   #+begin_src ocaml :tangle (eval ml) :exports none
let a0 = 0.529_177_210_67
let a0_inv = 1. /. a0
let ha_to_ev = 27.211_386_02
let ev_to_ha = 1. /. ha_to_ev
   #+end_src