A Collection of simple ppx extensions.

Getenv

ppx_getenv.ml :: A Simple compile time text generator [fn:1].

Addone

ppx_addone.ml :: Deep map 1+ for constant integers at compile time. i.e., 1 + 2 –> 2 + 3. Referenced [fn:2] but didn’t follow completely.

let _ = [%addone 1 + 2]
let _ = [%addone 1 * (2 + 3 * 4)]

let _ = 2 + 3
let _ = 2 * (3 + (4 * 5))

Equiv

ppx_equiv.ml :: A simple translator of bi-imply to conjunction of implications. a <==> b to (a ==> b) && (b ==> a).

let (==>) a b = not (a && not b)

let (<==>) a b = (a ==> b) && (b ==> a)

(* I want to expand <==> in this.*)
let equiv_theorem a b c =
  [%equiv ((a <==> b) <==> c) <==> (a <==> (b <==> c))]

let _ = [%equiv true <==> false]    

let (==>) a b = not (a && (not b))
let (<==>) a b = (a ==> b) && (b ==> a)
let equiv_theorem a b c =
  (((((a ==> b) && (b ==> a)) ==> c) && (c ==> ((a ==> b) && (b ==> a)))) ==>
     ((a ==> ((b ==> c) && (c ==> b))) && (((b ==> c) && (c ==> b)) ==> a)))
    &&
    (((a ==> ((b ==> c) && (c ==> b))) && (((b ==> c) && (c ==> b)) ==> a))
       ==>
       ((((a ==> b) && (b ==> a)) ==> c) && (c ==> ((a ==> b) && (b ==> a)))))
let _ = (true ==> false) && (false ==> true)

Arith

ppx_arith.ml :: A rewriter for arithmetic expressions.

let _ = [%arith 1 + (2 * 3) - (4 / 7)]

let _ = Sub (Add 1 (Mul 2 3)) (Div 4 7)

Footnotes

[fn:2] https://www.victor.darvariu.me/jekyll/update/2018/06/19/ppx-tutorial.html

[fn:1] https://whitequark.org/blog/2014/04/16/a-guide-to-extension-points-in-ocaml/