(access coll key)
  coll: any type
  key: any type
  returns any type

Retrieves an item from a collection.

• When coll is an array or string, key must be an integer. Positive integers count forwards from the deque's first element, starting from 0, while negative integers count backwards from the deque's last element, starting from -1.
• When coll is a table, key can be any value. See keys-eqv? for a discussion of how table keys are tested for equivalence.
• When coll is an object or class, key must be a symbol. Fields, constants and properties are bound both to a fully-qualified name, like State:x, and an unqualified name, like x.

The ? special syntax can be used to perform fallible indexing: [coll (? key)]. In that case, if the index key is not present, the function succeeds and returns #n.

When coll is a deque, slicing syntax is supported: [deq i : j], where either i or j may be absent. This returns a newly-allocated, mutable deque which contains all of the elements from i inclusive to j exclusive. Negative indexes are supported.

When key is an iterator, this function returns a new iterator which produces [coll item] for each item produced by key.

(access coll key) is usually abbreviated as [coll key].