Chapter 9 : Records

Records are like tuples but with named parameters. In other words, they hold a set of key/data pairs. To instantiate a record, you must first declare its type as follows :

type user = {
  id       : nat,
  is_admin : bool,
  name     : string

And here is how to define an associated record value :

let alice : user = {
  id       : 1n,
  is_admin : true,
  name     : "Alice"


You can access the whole record or get one key in particular by using the . operator:

let alice_admin : bool = alice.is_admin;


The syntax for the functional updates of record in ReasonLIGO follows that of ReasonML. You can modify values in a record as follows :

let change_name = ( u : user) : user =>{ ...u, name : "Mark" };

⚠️ Note that user has not been changed by the function. Rather, the function returned a nameless new version of it with the modified name.

⚠️ Notice the operator that destructures the record u into a nameless set of (key, value) pairs

Nested updates

A unique feature of LIGO is the ability to perform nested updates on records.

For example if you have the following record structure:

type color =
| Green;

type preferences = {
  color : color,
  other : int

type account = {
  id : int,
  preferences : preferences

You can update the nested record with the following code:

let change_color_preference = (account : account, color : color): account =>
  { ...account, preferences.color: color };

Your mission

1- Refactor the type of coordinates as a record instead of a tuple. Name the parameters x, y and z.

2- Refactor earth_coordinates with the record type.

2- Refactor the modified_earth_coordinates constant as a record (copy of earth_coordinates) with its third component changed to 5.