6.37 Indexables🔗ℹ

An indexable value is one that supports […] afterward to extract an element at the index within […]. Maps, lists, arrays, sets, strings, and byte strings are all indexable, as are instances of classes that implement Indexable.

With an assign_op, for a mutable indexable object (such as an array, map, set, or MutableIndexable object), the index element is assigned to the value based on the operator and rhs_expr. The expression result is #void in the case of := as assign_op.

See also use_static.

The #%index form is implicitly used when […] is used in after another expression or repetition in an expression or repetition position. See also Implicit Forms.

> {"a": 1, "b": 2}["a"]

1

> {"a": 1, "b": 2} #%index ["a"]

1

An interface that a class can implement (publicly or privately) to make instances of the class work with #%index. As an annotation, Indexable matches all indexable objects, not just instances of classes that publicly implement the Indexable interface.

The interface has a single abstract method:

• get(index) — the index value is the second argument to #%index, which is normally written within […]. The result of the get method is the result of the index form.

An interface that extends Indexable to add support for assignment with #%index. As an annotation, MutableIndexable matches all mutable indexable objects.

The interface has one additional abstract method: