Arrays keep ordered values. Slice helpers from the standard library copy, join, and extend those values.

let Slice := import "@std/collections/slice";
let values := [1, 2, 3];
Slice.concat[Int](values, [4]);

Array literals

let values := [1, 2, 3];
let extended := [0, ...values, 4];

Array spread uses ... to copy existing items into a new array literal.

Stdlib collection helpers

let Slice := import "@std/collections/slice";
let values := [1, 2, 3];
Slice.concat[Int](values, [4]);

Use helpers when the operation has a name. Use literals for small, obvious values.

Ranges describe bounds. Index and slice operations decide how those bounds apply to an array.

let firstThree := 0..<3;

Keep indexes named when the number has meaning, such as headerRows or previewLimit.