Using the `@tailcall` annotation in ReasonML

tailcall.re

let sum = n => {
  let rec loop = (n, k) =>
    if (n == 0) {
      k(0);
    } else {
      ([@tailcall] loop)(n - 1, x => k(x + n));
    };
  ([@tailcall] loop)(n, x => x);
};

unannotted.re

let sum = n => {
  let rec loop = (n, k) =>
    if (n == 0) {
      k(0);
    } else {
      loop(n - 1, x => k(x + n));
    };
  loop(n, x => x);
};

How do you test if this reasonml function is tail recursive. The simple version show you the unannottated function and usingTailCall.re show its annotated in reasonml.

Call in terminal with:

ocamlc -annot -o tailCall -pp "refmt -p ml" -impl tailCall.re

You can check where the tail calls are with:

grep call -A1 tailCall.annot 

Source: https://stackoverflow.com/a/40401233/2336356
Sketch: https://sketch.sh/s/eBl2Z0Wvd21azKu6SFzb9j/