Web Development with ReasonML

Using Lists

To create a list, you um… list the elements within square brackets. Unlike tuples, whose elements may be of different types, a list’s elements must all have the same type. Lists in ReasonML are immutable. Once you create a list, you can’t change the contents of an individual element. Instead, all of the list manipulation functions we’ll look at return a brand-new list. Let’s create and display a short list of integers:

collections/src/IntList.re

let example = [10, 11, 12];
Js.log(example);

With this rather surprising result:

you@computer:~/book_projects/collections> node src/IntList.bs.js
[ 10, [ 11, [ 12, 0 ] ] ]

What we’re seeing is a reflection of the internal form of a list. If we had more than three elements ...