Web Development with ReasonML

Grouping Heterogeneous Data with Tuples

The simplest form of collection is the tuple, which consists of a series of values in parentheses. The classic example of a tuple is for use as a pair of (x, y) coordinates:

collections/src/Coordinates.re

type coord = (float, float);

let distance = (p0: coord, p1: coord) : float => {
  let (x0, y0) = p0;
  let (x1, y1) = p1;
  sqrt((x0 -. x1) ** 2.0 +. (y0 -. y1) ** 2.0)
};

let startPoint = (3.5, 4.6);
let endPoint = (0.5, 9.6);
let result = distance(startPoint, endPoint);
Js.log(result);  /* output: 5.830951894845301 */

Pay special attention to the let bindings in the distance function. They use destructuring to extract ...