Book

Collections and ranges

Use lists for sequences, products for fields, and ranges for inclusive integer spans.

Sequences are lists

A list is Echo’s core ordered collection. Index it for direct access or iterate when order matters. Lists are shared objects, so mutation through a parameter or alias is deliberate and visible to the caller.

$ bump_first = (items) {
    ~ items[0] = items[0] + 1
    ^ items[0]
}

$ values = [10, 20, 30]
$ first = bump_first(values)

Products group fields

An anonymous product is useful for a small bundle returned or passed as one value. Reach for a named struct when the shape is part of the domain, needs defaults or methods, or must participate in a type match. Neither form is a general dictionary.

$ coordinate = { x: 4, y: 7 }
$ horizontal = coordinate.x

Ranges compose

A range is an ordinary value. The same inclusive 1..10 span can be bound, iterated, passed, or used for membership in a match arm.