Clojure collection quirks - A REFERENCE

This is a reference of Clojure’s default data structures and the most common predicates.

Functions

This table contains the most common predicates applied to the core collections.

		Seq				Vector		Map		Set
	nil	'(1 2 3)	(range 5)	(range) (lazy-seq) (cons 1 ())	Persistent Queue/EMPTY	[1 2 3]	(last {1 1})	(hash-map) (array-map)	(sorted-map)	#{}	(sorted-set)
type	nil	Persistent List	LongRange	Iterate or LazySeq or Cons	Persistent Queue	Persistent Vector	MapEntry	Persistent ArrayMap or HashMap	Persistent TreeMap	Persistent HashSet	Persistent TreeSet
coll?	false	true	true	true	true	true	true	true	true	true	true
counted?	false	true	true	false	true	true	true	true	true	true	true
ifn?	false	false	false	false	false	true	true	true	true	true	true
associative?	false	false	false	false	false	true	true	true	true	false	false
map?	false	false	false	false	false	false	false	true	true	false	false
sequential?	false	true	true	true	true	true	true	false	false	false	false
list?	false	true	false	false	true	false	false	false	false	false	false
seq?	false	true	true	true	false	false	false	false	false	false	false
reversible?	false	false	false	false	false	true	true	false	true	false	true
vector?	false	false	false	false	false	true	true	false	false	false	false
map-entry?	false	false	false	false	false	false	true	false	false	false	false
map?	false	false	false	false	false	false	false	true	true	false	false
set?	false	false	false	false	false	false	false	false	false	true	true
sorted?	false	false	false	false	false	false	false	false	true	false	true

Interfaces

An incomplete list of some of the most commonly used default Clojure interfaces found in the clojure.lang package.

IMeta

The object has meta information accessible via the (meta x) function.

IObj

Indicates that meta information can be added to object (with-meta function).

Counted

This collection supports fast counting ((count x) function call).

IEditableCollection

A transient version of the collection can be created with the (transient x) call.

IFn

Indicates that he object can be called just like a function.

IKeywordLookup

A collection supports indexing by keywords.

ILookup

Collection supports access by index (via get function with default value).

IPending

Supports realized? function.

IPersistentCollection

Persistent collections have support for conj, empty, count, equals functions.

ISeq

Sequences have support for first, next, rest, cons functions.