Web Development with ReasonML

Working with option Values

In a program of any significant length, we’ll eventually end up passing option values through a series of functions, some of which accept and/or return option values, and some that don’t. Consider these functions:

datatypes/src/BeltExamples.re

let toFloat = (str: string) : option(float) => {
  let result =  (Js.Float.fromString(str));
  if (Js.Float.isNaN(result)) {
    None
  } else {
    Some(result)
  }
};

let cube = (x: float) : float =>  x *. x *. x;

let reciprocal = (x: float) : option(float) => {
  if (x !== 0.0) {
    Some(1.0 /. x)
  } else {
    None
  }
};

We’d like to stitch these together into a program that performs the following ...