Collections

count

Returns the number of items in the collection. (count nil) returns 0. Also works on strings, arrays, and Maps

empty

Returns an empty collection of the same category as coll, or nil

find

Returns the map entry for key, or nil if key not present.

first

Returns the first item in the collection. Calls seq on its argument. If coll is nil, returns nil.

get

Returns the value mapped to key, not-found or nil if key not present in associative collection, set, string, array, or I...

get-in

Returns the value in a nested associative structure, where ks is a sequence of keys. Returns nil if the key is not prese...

key

Returns the key of the map entry.

keys

Returns a sequence of the map's keys, in the same order as (seq map).

last

Return the last item in coll, in linear time

next

Returns a seq of the items after the first. Calls seq on its argument. If there are no more items, returns nil

nth

Returns the value at the index. get returns nil if index out of bounds, nth throws an exception unless not-found is supp...

peek

For a list or queue, same as first, for a vector, same as, but much more efficient than, last. If the collection is empt...

rest

Returns a possibly empty seq of the items after the first. Calls seq on its argument.

second

Same as (first (next x))

seq

Returns a seq on the collection. If the collection is empty, returns nil. (seq nil) returns nil. seq also works on Stri...

sequence

Coerces coll to a (possibly empty) sequence, if it is not already one. Will not force a lazy seq. (sequence nil) yields ...

val

Returns the value in the map entry.

vals

Returns a sequence of the map's values, in the same order as (seq map).

array-map

keyval => key val Returns a new array map with supplied mappings.

cycle

Returns a lazy (infinite!) sequence of repetitions of the items in coll.

hash-map

keyval => key val Returns a new hash map with supplied mappings.

hash-set

Returns a new hash set with supplied keys. Any equal keys are handled as if by repeated uses of conj.

iterate

Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of side-effects

lazy-seq

Takes a body of expressions that returns an ISeq or nil, and yields a ISeqable object that will invoke the body only the...

list

Creates a new list containing the items.

list*

Creates a new list containing the items prepended to the rest, the last of which will be treated as a sequence.

range

Returns a lazy seq of nums from start (inclusive) to end (exclusive), by step, where start defaults to 0, step to 1, and...

repeat

Returns a lazy (infinite!, or length n if supplied) sequence of xs.

repeatedly

Takes a function of no args, presumably with side effects, and returns an infinite (or length n if supplied) lazy sequen...

set

Returns a set of the distinct elements of coll.

sorted-map

keyval => key val Returns a new sorted map with supplied mappings.

sorted-map-by

keyval => key val Returns a new sorted map with supplied mappings, using the supplied comparator.

sorted-set

Returns a new sorted set with supplied keys.

sorted-set-by

Returns a new sorted set with supplied keys, using the supplied comparator.

vec

Creates a new vector containing the contents of coll. JavaScript arrays will be aliased and should not be modified.

vector

Creates a new vector containing the args.

zipmap

Returns a map with the keys mapped to the corresponding vals.

assoc

assoc[iate]. When applied to a map, returns a new map of the same (hashed/sorted) type, that contains the mapping of key...

assoc-in

Associates a value in a nested associative structure, where ks is a sequence of keys and v is the new value and returns ...

conj

conj[oin]. Returns a new collection with the xs 'added'. (conj nil item) returns (item). (conj coll) returns coll. (conj...

cons

Returns a new seq where x is the first element and coll is the rest.

disj

disj[oin]. Returns a new set of the same (hashed/sorted) type, that does not contain key(s).

dissoc

dissoc[iate]. Returns a new map of the same (hashed/sorted) type, that does not contain a mapping for key(s).

pop

For a list or queue, returns a new list/queue without the first item, for a vector, returns a new vector without the las...

update

'Updates' a value in an associative structure, where k is a key and f is a function that will take the old value and any...

update-in

'Updates' a value in a nested associative structure, where ks is a sequence of keys and f is a function that will take t...

associative?

Returns true if coll implements IAssociative

chunked-seq?

Return true if x satisfies IChunkedSeq.

coll?

Returns true if x satisfies ICollection

contains?

Returns true if key is present in the given collection, otherwise returns false. Note that for numerically indexed coll...

counted?

Returns true if coll implements count in constant time

distinct?

Returns true if no two of the arguments are =

empty?

Returns true if coll has no items. To check the emptiness of a seq, please use the idiom (seq x) rather than (not (empty...

every?

Returns true if (pred x) is logical true for every x in coll, else false.

indexed?

Returns true if coll implements nth in constant time

list?

Returns true if x implements IList

map-entry?

Returns true if x satisfies IMapEntry

map?

Return true if x satisfies IMap

not-any?

Returns false if (pred x) is logical true for any x in coll, else true.

not-empty

If coll is empty, returns nil, else coll

not-every?

Returns false if (pred x) is logical true for every x in coll, else true.

record?

Return true if x satisfies IRecord

reversible?

Returns true if coll satisfies? IReversible.

seq?

Return true if s satisfies ISeq

seqable?

Return true if the seq function is supported for s

sequential?

Returns true if coll satisfies ISequential

set?

Returns true if x satisfies ISet

some

Returns the first logical true value of (pred x) for any x in coll, else nil. One common idiom is to use a set as pred,...

sorted?

Returns true if coll satisfies ISorted

vector?

Return true if x satisfies IVector

Cat

CollFold

append!

.adds x to acc and returns acc

cat

A high-performance combining fn that yields the catenation of the reduced values. The result is reducible, foldable, seq...

drop

Elides the first n values from the reduction of coll.

filter

Retains values in the reduction of coll for which (pred val) returns logical true. Foldable.

flatten

Takes any nested combination of sequential things (lists, vectors, etc.) and returns their contents as a single, flat ...

fold

Reduces a collection using a (potentially parallel) reduce-combine strategy. The collection is partitioned into groups o...

foldcat

Equivalent to (fold cat append! coll)

folder

Given a foldable collection, and a transformation function xf, returns a foldable collection, where any supplied reducin...

map

Applies f to every value in the reduction of coll. Foldable.

mapcat

Applies f to every value in the reduction of coll, concatenating the result colls of (f val). Foldable.

monoid

Builds a combining fn out of the supplied operator and identity constructor. op must be associative and ctor called with...

reduce

Like core/reduce except: When init is not provided, (f) is used. Maps are reduced with reduce-kv

reducer

Given a reducible collection, and a transformation function xf, returns a reducible collection, where any supplied reduc...

remove

Removes values in the reduction of coll for which (pred val) returns logical true. Foldable.

take

Ends the reduction of coll after consuming n values.

take-while

Ends the reduction of coll when (pred val) returns logical false.

difference

Return a set that is the first set without elements of the remaining sets

index

Returns a map of the distinct values of ks in the xrel mapped to a set of the maps in xrel with the corresponding values...

intersection

Return a set that is the intersection of the input sets

join

When passed 2 rels, returns the rel corresponding to the natural join. When passed an additional keymap, joins on the co...

map-invert

Returns the map with the vals mapped to the keys.

project

Returns a rel of the elements of xrel with only the keys in ks

rename

Returns a rel of the maps in xrel with the keys in kmap renamed to the vals in kmap

rename-keys

Returns the map with the keys in kmap renamed to the vals in kmap

select

Returns a set of the elements for which pred is true

subset?

Is set1 a subset of set2?

superset?

Is set1 a superset of set2?

union

Return a set that is the union of the input sets

butlast

Return a seq of all but the last item in coll, in linear time

cat

A transducer which concatenates the contents of each input, which must be a collection, into the reduction.

concat

Returns a lazy seq representing the concatenation of the elements in the supplied colls.

dedupe

Returns a lazy sequence removing consecutive duplicates in coll. Returns a transducer when no collection is provided.

distinct

Returns a lazy sequence of the elements of coll with duplicates removed. Returns a stateful transducer when no collectio...

doall

When lazy sequences are produced via functions that have side effects, any effects other than those needed to produce th...

dorun

When lazy sequences are produced via functions that have side effects, any effects other than those needed to produce th...

doseq

Repeatedly executes body (presumably for side-effects) with bindings and filtering as provided by "for". Does not retai...

drop

Returns a laziness-preserving sequence of all but the first n items in coll. Returns a stateful transducer when no colle...

drop-last

Return a lazy sequence of all but the last n (default 1) items in coll

drop-while

Returns a lazy sequence of the items in coll starting from the first item for which (pred item) returns logical false. ...

eduction

Returns a reducible/iterable application of the transducers to the items in coll. Transducers are applied in order as if...

filter

Returns a lazy sequence of the items in coll for which (pred item) returns logical true. pred must be free of side-effec...

filterv

Returns a vector of the items in coll for which (pred item) returns logical true. pred must be free of side-effects.

flatten

Takes any nested combination of sequential things (lists, vectors, etc.) and returns their contents as a single, flat se...

for

List comprehension. Takes a vector of one or more binding-form/collection-expr pairs, each followed by zero or more mo...

frequencies

Returns a map from distinct items in coll to the number of times they appear.

group-by

Returns a map of the elements of coll keyed by the result of f on each element. The value at each key will be a vector o...

interleave

Returns a lazy seq of the first item in each coll, then the second etc.

interpose

Returns a lazy seq of the elements of coll separated by sep. Returns a stateful transducer when no collection is provide...

into

Returns a new coll consisting of to-coll with all of the items of from-coll conjoined. A transducer may be supplied.

keep

Returns a lazy sequence of the non-nil results of (f item). Note, this means false return values will be included. f mu...

keep-indexed

Returns a lazy sequence of the non-nil results of (f index item). Note, this means false return values will be included....

map

Returns a lazy sequence consisting of the result of applying f to the set of first items of each coll, followed by apply...

map-indexed

Returns a lazy sequence consisting of the result of applying f to 0 and the first item of coll, followed by applying f t...

mapcat

Returns the result of applying concat to the result of applying map to f and colls. Thus function f should return a col...

mapv

Returns a vector consisting of the result of applying f to the set of first items of each coll, followed by applying f t...

merge

Returns a map that consists of the rest of the maps conj-ed onto the first. If a key occurs in more than one map, the m...

merge-with

Returns a map that consists of the rest of the maps conj-ed onto the first. If a key occurs in more than one map, the m...

nthnext

Returns the nth next of coll, (seq coll) when n is 0.

nthrest

Returns the nth rest of coll, coll when n is 0.

partition

Returns a lazy sequence of lists of n items each, at offsets step apart. If step is not supplied, defaults to n, i.e. th...

partition-all

Returns a lazy sequence of lists like partition, but may include partitions with fewer than n items at the end. Returns...

partition-by

Applies f to each value in coll, splitting it each time f returns a new value. Returns a lazy seq of partitions. Retur...

random-sample

Returns items from coll with random probability of prob (0.0 - 1.0). Returns a transducer when no collection is provide...

reduce

f should be a function of 2 arguments. If val is not supplied, returns the result of applying f to the first 2 items in ...

reduce-kv

Reduces an associative collection. f should be a function of 3 arguments. Returns the result of applying f to init, the ...

reductions

Returns a lazy seq of the intermediate values of the reduction (as per reduce) of coll by f, starting with init.

remove

Returns a lazy sequence of the items in coll for which (pred item) returns logical false. pred must be free of side-effe...

replace

Given a map of replacement pairs and a vector/collection, returns a vector/seq with any elements = a key in smap replace...

reverse

Returns a seq of the items in coll in reverse order. Not lazy.

rseq

Returns, in constant time, a seq of the items in rev (which can be a vector or sorted-map), in reverse order. If rev is ...

rsubseq

sc must be a sorted collection, test(s) one of <, <=, > or >=. Returns a reverse seq of those entries with keys ek for w...

run!

Runs the supplied procedure (via reduce), for purposes of side effects, on successive items in the collection. Returns n...

select-keys

Returns a map containing only those entries in map whose key is in keys

shuffle

Return a random permutation of coll

sort

Returns a sorted sequence of the items in coll. Comp can be boolean-valued comparison function, or a -/0/+ valued compar...

sort-by

Returns a sorted sequence of the items in coll, where the sort order is determined by comparing (keyfn item). Comp can ...

split-at

Returns a vector of [(take n coll) (drop n coll)]

split-with

Returns a vector of [(take-while pred coll) (drop-while pred coll)]

subseq

sc must be a sorted collection, test(s) one of <, <=, > or >=. Returns a seq of those entries with keys ek for which (te...

take

Returns a lazy sequence of the first n items in coll, or all items if there are fewer than n. Returns a stateful transd...

take-last

Returns a seq of the last n items in coll. Depending on the type of coll may be no better than linear time. For vector...

take-nth

Returns a lazy seq of every nth item in coll. Returns a stateful transducer when no collection is provided.

take-while

Returns a lazy sequence of successive items from coll while (pred item) returns logical true. pred must be free of side-...

transduce

reduce with a transformation of f (xf). If init is not supplied, (f) will be called to produce it. f should be a reducin...

tree-seq

Returns a lazy sequence of the nodes in a tree, via a depth-first walk. branch? must be a fn of one arg that returns tru...

update-keys

m f => {(f k) v ...} Given a map m and a function f of 1-argument, returns a new map whose keys are the result of applyi...

update-vals

m f => {k (f v) ...} Given a map m and a function f of 1-argument, returns a new map where the keys of m are mapped to r...

assoc!

When applied to a transient map, adds mapping of key(s) to val(s). When applied to a transient vector, sets the val at i...

conj!

Adds val to the transient collection, and return tcoll. The 'addition' may happen at different 'places' depending on the...

disj!

disj[oin]. Returns a transient set of the same (hashed/sorted) type, that does not contain key(s).

dissoc!

Returns a transient map that doesn't contain a mapping for key(s).

persistent!

Returns a new, persistent version of the transient collection, in constant time. The transient collection cannot be used...

pop!

Removes the last item from a transient vector. If the collection is empty, throws an exception. Returns tcoll

transient

Returns a new, transient version of the collection, in constant time.