ClojureDocs

Clojure Core

Float TOC

Quick Ref for Clojure Core

Adapted from Johannes Friestad's excellent quick ref.

Simple Values

Numbers

Simple Values

Arithmetic

Simple Values > Numbers

+ Returns the sum of nums. (+) returns 0. 1 ex.
- If no ys are supplied, returns the negation of x, else subtracts th 1 ex.
* Returns the product of nums. (*) returns 1. 1 ex.
/ If no denominators are supplied, returns 1/numerator, else returns 1 ex.
quot quot[ient] of dividing numerator by denominator. 2 ex.
rem remainder of dividing numerator by denominator. 2 ex.
mod Modulus of num and div. Truncates toward negative infinity. 1 ex.
inc Returns a number one greater than num. 1 ex.
dec Returns a number one less than num. 1 ex.
max Returns the greatest of the nums. 1 ex.
min Returns the least of the nums. 1 ex.
with-precision Sets the precision and rounding mode to be used for BigDecimal operat 1 ex.

Compare

Simple Values > Numbers

= Equality. Returns true if x equals y, false if not. Same as Java x. 1 ex.
== Returns non-nil if nums all have the same value, otherwise false 1 ex.
not= Same as (not (= obj1 obj2)) 1 ex.
< Returns non-nil if nums are in monotonically increasing order, othe 1 ex.
> Returns non-nil if nums are in monotonically decreasing order, othe 1 ex.
<= Returns non-nil if nums are in monotonically non-decreasing order, 1 ex.
>= Returns non-nil if nums are in monotonically non-increasing order, 1 ex.

Bitwise Operations

Simple Values > Numbers

bit-and Bitwise and 1 ex.
bit-or Bitwise or 1 ex.
bit-xor Bitwise exclusive or 1 ex.
bit-flip Flip bit at index n 1 ex.
bit-not Bitwise complement 1 ex.
bit-clear Clear bit at index n 1 ex.
bit-set Set bit at index n 1 ex.
bit-shift-left Bitwise shift left 1 ex.
bit-shift-right Bitwise shift right 2 ex.
bit-test Test bit at index n 1 ex.

Cast

Simple Values > Numbers

byte Coerce to byte 1 ex.
short Coerce to short 1 ex.
int Coerce to int 1 ex.
long Coerce to long 2 ex.
float Coerce to float 1 ex.
double Coerce to double 1 ex.
bigint Coerce to BigInteger 1 ex.
bigdec Coerce to BigDecimal 1 ex.
num Coerce to Number 1 ex.
rationalize returns the rational value of num 1 ex.

Test

Simple Values > Numbers

nil? Returns true if x is nil, false otherwise. 1 ex.
identical? Tests if 2 arguments are the same object 1 ex.
zero? Returns true if num is zero, else false 1 ex.
pos? Returns true if num is greater than zero, else false 1 ex.
neg? Returns true if num is less than zero, else false 1 ex.
even? Returns true if n is even, throws an exception if n is not an integer 1 ex.
odd? Returns true if n is odd, throws an exception if n is not an integer 1 ex.

Symbols / Keywords

Simple Values

Create

Simple Values > Symbols / Keywords

keyword Returns a Keyword with the given namespace and name. Do not use : 1 ex.
symbol Returns a Symbol with the given namespace and name. 1 ex.

Use

Simple Values > Symbols / Keywords

name Returns the name String of a string, symbol or keyword. 1 ex.
intern Finds or creates a var named by the symbol name in the namespace ns 1 ex.
namespace Returns the namespace String of a symbol or keyword, or nil if not pr 1 ex.

Test

Simple Values > Symbols / Keywords

keyword? Return true if x is a Keyword 1 ex.
symbol? Return true if x is a Symbol 1 ex.

Strings / Characters

Simple Values

Create

Simple Values > Strings / Characters

str With no args, returns the empty string. With one arg x, returns x.t 2 ex.
print-str print to a string, returning it 1 ex.
println-str println to a string, returning it 1 ex.
pr-str pr to a string, returning it 1 ex.
prn-str prn to a string, returning it 1 ex.
with-out-str Evaluates exprs in a context in which *out* is bound to a fresh Str 1 ex.

Use

Simple Values > Strings / Characters

count Returns the number of items in the collection. (count nil) returns 1 ex.
get Returns the value mapped to key, not-found or nil if key not present. 1 ex.
subs Returns the substring of s beginning at start inclusive, and ending 1 ex.
format Formats a string using java.lang.String.format, see java.util.Formatt 1 ex.

Cast / Test

Simple Values > Strings / Characters

char Coerce to char 1 ex.
char? Return true if x is a Character 1 ex.
string? Return true if x is a String 1 ex.

Regular Expressions

Simple Values

Create

Simple Values > Regular Expressions

re-pattern Returns an instance of java.util.regex.Pattern, for use, e.g. in re 1 ex.
re-matcher Returns an instance of java.util.regex.Matcher, for use, e.g. in re 1 ex.

Use

Simple Values > Regular Expressions

re-find Returns the next regex match, if any, of string to pattern, using j 2 ex.
re-matches Returns the match, if any, of string to pattern, using java.util.re 1 ex.
re-seq Returns a lazy sequence of successive matches of pattern in string, 2 ex.
re-groups Returns the groups from the most recent match/find. If there are no 1 ex.

Operations

Flow Control

Operations

Normal

Operations > Flow Control

if Please see http://clojure.org/special_forms#if 1 ex.
if-not Evaluates test. If logical false, evaluates and returns then expr, 2 ex.
if-let bindings => binding-form test If test is true, evaluates then with 3 ex.
when Evaluates test. If logical true, evaluates body in an implicit do. 2 ex.
when-not Evaluates test. If logical false, evaluates body in an implicit do. 1 ex.
when-let bindings => binding-form test When test is true, evaluates body wi 1 ex.
when-first bindings => x xs Same as (when (seq xs) (let [x (first xs)] body)) 1 ex.
cond Takes a set of test/expr pairs. It evaluates each test one at a tim 2 ex.
condp Takes a binary predicate, an expression, and a set of clauses. Each 4 ex.
case Takes an expression, and a set of clauses. Each clause can take th 1 ex.
do Please see http://clojure.org/special_forms#do 1 ex.
eval Evaluates the form data structure (not text!) and returns the result. 2 ex.
loop Evaluates the exprs in a lexical context in which the symbols in th 2 ex.
recur Please see http://clojure.org/special_forms#recur 2 ex.
trampoline trampoline can be used to convert algorithms requiring mutual recur 1 ex.
while Repeatedly executes body while test expression is true. Presumes so 1 ex.

Exceptional

Operations > Flow Control

try Please see http://clojure.org/special_forms#try 1 ex.
catch Please see http://clojure.org/special_forms#try 1 ex.
finally Please see http://clojure.org/special_forms#finally 1 ex.
throw Please see http://clojure.org/special_forms#throw 1 ex.
assert Evaluates expr and throws an exception if it does not evaluate to lo 1 ex.

Delay

Operations > Flow Control

delay Takes a body of expressions and yields a Delay object that will inv 1 ex.
delay? returns true if x is a Delay created with delay 1 ex.
deref Also reader macro: @ref/@agent/@var/@atom/@delay/@future. Within a tr 1 ex.
force If x is a Delay, returns the (possibly cached) value of its expressio 2 ex.

Function Based

Operations > Flow Control

repeatedly Takes a function of no args, presumably with side effects, and retu 2 ex.
iterate Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of 3 ex.

Sequence Based

Operations > Flow Control

dotimes bindings => name n Repeatedly executes body (presumably for side-e 1 ex.
doseq Repeatedly executes body (presumably for side-effects) with binding 5 ex.
for List comprehension. Takes a vector of one or more binding-form/col 6 ex.

Laziness

Operations > Flow Control

lazy-seq Takes a body of expressions that returns an ISeq or nil, and yields 1 ex.
lazy-cat Expands to code which yields a lazy sequence of the concatenation o 1 ex.
doall When lazy sequences are produced via functions that have side effec 1 ex.
dorun When lazy sequences are produced via functions that have side effec 1 ex.

Type Inspection

Operations

Clojure Types

Operations > Type Inspection

type Returns the :type metadata of x, or its Class if none 2 ex.
extends? Returns true if atype extends protocol 0 ex.
satisfies? Returns true if x satisfies the protocol 1 ex.

Java Types

Operations > Type Inspection

class Returns the Class of x 1 ex.
bases Returns the immediate superclass and direct interfaces of c, if any 1 ex.
supers Returns the immediate and indirect superclasses and interfaces of c, 1 ex.
class? Returns true if x is an instance of Class 1 ex.
instance? Evaluates x and tests if it is an instance of the class c. Return 2 ex.
isa? Returns true if (= child parent), or child is directly or indirectly 2 ex.
cast Throws a ClassCastException if x is not a c, else returns x. 1 ex.

Concurrency

Operations

General

Operations > Concurrency

deref Also reader macro: @ref/@agent/@var/@atom/@delay/@future. Within a tr 1 ex.
get-validator Gets the validator-fn for a var/ref/agent/atom. 0 ex.
set-validator! Sets the validator-fn for a var/ref/agent/atom. validator-fn must be 0 ex.

Atoms

Operations > Concurrency

atom Creates and returns an Atom with an initial value of x and zero or 1 ex.
swap! Atomically swaps the value of atom to be: (apply f current-value-of 2 ex.
reset! Sets the value of atom to newval without regard for the current val 1 ex.
compare-and-set! Atomically sets the value of atom to newval if and only if the curr 1 ex.

Refs

Operations > Concurrency

ref Creates and returns a Ref with an initial value of x and zero or mo 1 ex.
sync transaction-flags => TBD, pass nil for now Runs the exprs (in an i 0 ex.
dosync Runs the exprs (in an implicit do) in a transaction that encompasses 1 ex.
ref-set Must be called in a transaction. Sets the value of ref. Returns val 1 ex.
alter Must be called in a transaction. Sets the in-transaction-value of r 1 ex.
commute Must be called in a transaction. Sets the in-transaction-value of r 0 ex.
ensure Must be called in a transaction. Protects the ref from modification 0 ex.
io! If an io! block occurs in a transaction, throws an IllegalStateExce 0 ex.
ref-history-count Returns the history count of a ref 0 ex.
ref-max-history Gets the max-history of a ref, or sets it and returns the ref 0 ex.
ref-min-history Gets the min-history of a ref, or sets it and returns the ref 0 ex.

Agents

Operations > Concurrency

agent Creates and returns an agent with an initial value of state and zer 1 ex.
send Dispatch an action to an agent. Returns the agent immediately. Subs 1 ex.
send-off Dispatch a potentially blocking action to an agent. Returns the age 1 ex.
await Blocks the current thread (indefinitely!) until all actions dispatc 1 ex.
await-for Blocks the current thread until all actions dispatched thus far (fr 0 ex.
agent-error Returns the exception thrown during an asynchronous action of the a 0 ex.
restart-agent When an agent is failed, changes the agent state to new-state and t 0 ex.
shutdown-agents Initiates a shutdown of the thread pools that back the agent system 0 ex.
*agent* The agent currently running an action on this thread, else nil 1 ex.
error-handler Returns the error-handler of agent a, or nil if there is none. See 0 ex.
set-error-handler! Sets the error-handler of agent a to handler-fn. If an action bein 0 ex.
error-mode Returns the error-mode of agent a. See set-error-mode! 0 ex.
set-error-mode! Sets the error-mode of agent a to mode-keyword, which must be eithe 0 ex.
release-pending-sends Normally, actions sent directly or indirectly during another action 0 ex.

Futures

Operations > Concurrency

future Takes a body of expressions and yields a future object that will in 2 ex.
future-call Takes a function of no args and yields a future object that will in 0 ex.
future-done? Returns true if future f is done 0 ex.
future-cancel Cancels the future, if possible. 0 ex.
future-cancelled? Returns true if future f is cancelled 0 ex.
future? Returns true if x is a future 0 ex.

Thread Local Values

Operations > Concurrency

bound-fn Returns a function defined by the given fntail, which will install th 0 ex.
bound-fn* Returns a function, which will install the same bindings in effect as 0 ex.
get-thread-bindings Get a map with the Var/value pairs which is currently in effect for t 0 ex.
push-thread-bindings WARNING: This is a low-level function. Prefer high-level macros like 0 ex.
pop-thread-bindings Pop one set of bindings pushed with push-binding before. It is an err 0 ex.
thread-bound? Returns true if all of the vars provided as arguments have thread-loc 0 ex.

Misc

Operations > Concurrency

locking Executes exprs in an implicit do, while holding the monitor of x. W 1 ex.
pcalls Executes the no-arg fns in parallel, returning a lazy sequence of t 1 ex.
pvalues Returns a lazy sequence of the values of the exprs, which are evalu 1 ex.
pmap Like map, except f is applied in parallel. Semi-lazy in that the pa 2 ex.
seque Creates a queued seq on another (presumably lazy) seq s. The queued 1 ex.
promise Alpha - subject to change. Returns a promise object that can be rea 1 ex.
deliver Alpha - subject to change. Delivers the supplied value to the promi 1 ex.
add-watch Alpha - subject to change. Adds a watch function to an agent/atom/v 1 ex.
remove-watch Alpha - subject to change. Removes a watch (set by add-watch) from 0 ex.

Functions

General

Functions

Create

Functions > General

fn (fn name? [params* ] exprs*) (fn name? ([params* ] exprs*)+) par 2 ex.
defn Same as (def name (fn [params* ] exprs*)) or (def name (fn ([para 3 ex.
defn- same as defn, yielding non-public def 1 ex.
definline Experimental - like defmacro, except defines a named function whose 0 ex.
identity Returns its argument. 6 ex.
constantly Returns a function that takes any number of arguments and returns x. 2 ex.
memfn Expands into code that creates a fn that expects to be passed an ob 1 ex.
comp Takes a set of functions and returns a fn that is the composition o 6 ex.
complement Takes a fn f and returns a fn that takes the same arguments as f, h 1 ex.
partial Takes a function f and fewer than the normal arguments to f, and re 2 ex.
juxt Alpha - name subject to change. Takes a set of functions and return 3 ex.
memoize Returns a memoized version of a referentially transparent function. T 1 ex.

Call

Functions > General

-> Threads the expr through the forms. Inserts x as the second item in 2 ex.
->> Threads the expr through the forms. Inserts x as the last item in t 1 ex.
apply Applies fn f to the argument list formed by prepending args to argseq 6 ex.

Test

Functions > General

fn? Returns true if x implements Fn, i.e. is an object created via fn. 2 ex.
ifn? Returns true if x implements IFn. Note that many data structures (e 1 ex.

Multifunctions

Functions

Create

Functions > Multifunctions

defmulti Creates a new multimethod with the associated dispatch function. Th 3 ex.
defmethod Creates and installs a new method of multimethod associated with disp 3 ex.

Inspect and Modify

Functions > Multifunctions

get-method Given a multimethod and a dispatch value, returns the dispatch fn t 1 ex.
methods Given a multimethod, returns a map of dispatch values -> dispatch fns 1 ex.
prefer-method Causes the multimethod to prefer matches of dispatch-val-x over dispa 0 ex.
prefers Given a multimethod, returns a map of preferred value -> set of other 0 ex.
remove-method Removes the method of multimethod associated with dispatch-value. 1 ex.
remove-all-methods Removes all of the methods of multimethod. 1 ex.

Macros

Functions

Create

Functions > Macros

defmacro Like defn, but the resulting function name is declared as a macro a 1 ex.
macroexpand Repeatedly calls macroexpand-1 on form until it no longer represent 1 ex.
macroexpand-1 If form represents a macro form, returns its expansion, else return 1 ex.
gensym Returns a new symbol with a unique name. If a prefix string is supp 2 ex.

Java Interop

Functions

Use

Functions > Java Interop

doto Evaluates x then calls all of the methods and functions with the va 2 ex.
.. form => fieldName-symbol or (instanceMethodName-symbol args*) Expa 1 ex.
set! Please see http://clojure.org/special_forms#set 1 ex.

Arrays

Functions > Java Interop

make-array Creates and returns an array of instances of the specified class of 2 ex.
object-array Creates an array of objects 1 ex.
boolean-array Creates an array of booleans 1 ex.
byte-array Creates an array of bytes 1 ex.
char-array Creates an array of chars 1 ex.
short-array Creates an array of shorts 1 ex.
int-array Creates an array of ints 1 ex.
long-array Creates an array of longs 1 ex.
float-array Creates an array of floats 1 ex.
double-array Creates an array of doubles 1 ex.
aclone Returns a clone of the Java array. Works on arrays of known types. 1 ex.
to-array Returns an array of Objects containing the contents of coll, which 1 ex.
to-array-2d Returns a (potentially-ragged) 2-dimensional array of Objects conta 2 ex.
into-array Returns an array with components set to the values in aseq. The array 1 ex.

Use

Functions > Java Interop

aget Returns the value at the index/indices. Works on Java arrays of all 1 ex.
aset Sets the value at the index/indices. Works on Java arrays of refere 1 ex.
aset-boolean Sets the value at the index/indices. Works on arrays of boolean. Retu 1 ex.
aset-char Sets the value at the index/indices. Works on arrays of char. Returns 1 ex.
aset-byte Sets the value at the index/indices. Works on arrays of byte. Returns 1 ex.
aset-int Sets the value at the index/indices. Works on arrays of int. Returns 1 ex.
aset-long Sets the value at the index/indices. Works on arrays of long. Returns 1 ex.
aset-short Sets the value at the index/indices. Works on arrays of short. Return 1 ex.
aset-float Sets the value at the index/indices. Works on arrays of float. Return 1 ex.
aset-double Sets the value at the index/indices. Works on arrays of double. Retur 1 ex.
alength Returns the length of the Java array. Works on arrays of all types. 1 ex.
amap Maps an expression across an array a, using an index named idx, and 1 ex.
areduce Reduces an expression across an array a, using an index named idx, 1 ex.

Cast

Functions > Java Interop

booleans Casts to boolean[] 0 ex.
bytes Casts to bytes[] 0 ex.
chars Casts to chars[] 0 ex.
ints Casts to int[] 0 ex.
shorts Casts to shorts[] 0 ex.
longs Casts to long[] 0 ex.
floats Casts to float[] 0 ex.
doubles Casts to double[] 0 ex.

Proxies

Functions

Create

Functions > Proxies

proxy class-and-interfaces - a vector of class names args - a (possibly 1 ex.
get-proxy-class Takes an optional single class followed by zero or more interfaces. 0 ex.
construct-proxy Takes a proxy class and any arguments for its superclass ctor and c 0 ex.
init-proxy Takes a proxy instance and a map of strings (which must correspond 0 ex.

Misc

Functions > Proxies

proxy-mappings Takes a proxy instance and returns the proxy's fn map. 0 ex.
proxy-super Use to call a superclass method in the body of a proxy method. Not 0 ex.
update-proxy Takes a proxy instance and a map of strings (which must correspond 1 ex.

Collections / Sequences

Collections

Collections / Sequences

Generic Operations

Collections / Sequences > Collections

count Returns the number of items in the collection. (count nil) returns 1 ex.
empty Returns an empty collection of the same category as coll, or nil 1 ex.
not-empty If coll is empty, returns nil, else coll 1 ex.
into Returns a new coll consisting of to-coll with all of the items of f 2 ex.
conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.

Content Tests

Collections / Sequences > Collections

contains? Returns true if key is present in the given collection, otherwise r 2 ex.
distinct? Returns true if no two of the arguments are = 1 ex.
empty? Returns true if coll has no items - same as (not (seq coll)). Pleas 3 ex.
every? Returns true if (pred x) is logical true for every x in coll, else 2 ex.
not-every? Returns false if (pred x) is logical true for every x in coll, else 1 ex.
some Returns the first logical true value of (pred x) for any x in coll, 7 ex.
not-any? Returns false if (pred x) is logical true for any x in coll, else t 1 ex.

Capabilities

Collections / Sequences > Collections

sequential? Returns true if coll implements Sequential 1 ex.
associative? Returns true if coll implements Associative 0 ex.
sorted? Returns true if coll implements Sorted 1 ex.
counted? Returns true if coll implements count in constant time 1 ex.
reversible? Returns true if coll implements Reversible 0 ex.

Type Tests

Collections / Sequences > Collections

coll? Returns true if x implements IPersistentCollection 2 ex.
seq? Return true if x implements ISeq 1 ex.
vector? Return true if x implements IPersistentVector 1 ex.
list? Returns true if x implements IPersistentList 1 ex.
map? Return true if x implements IPersistentMap 1 ex.
set? Returns true if x implements IPersistentSet 1 ex.

Vectors

Collections / Sequences

Create

Collections / Sequences > Vectors

vec Creates a new vector containing the contents of coll. 1 ex.
vector Creates a new vector containing the args. 3 ex.
vector-of Creates a new vector of a single primitive type t, where t is one o 1 ex.

Use

Collections / Sequences > Vectors

conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.
peek For a list or queue, same as first, for a vector, same as, but much 1 ex.
pop For a list or queue, returns a new list/queue without the first ite 1 ex.
get Returns the value mapped to key, not-found or nil if key not present. 1 ex.
assoc assoc[iate]. When applied to a map, returns a new map of the same 1 ex.
subvec Returns a persistent vector of the items in vector from start (incl 1 ex.
rseq Returns, in constant time, a seq of the items in rev (which can be 1 ex.

Lists

Collections / Sequences

Create

Collections / Sequences > Lists

list Creates a new list containing the items. 2 ex.
list* Creates a new list containing the items prepended to the rest, the 1 ex.

Use

Collections / Sequences > Lists

cons Returns a new seq where x is the first element and seq is the res 1 ex.
conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.
peek For a list or queue, same as first, for a vector, same as, but much 1 ex.
pop For a list or queue, returns a new list/queue without the first ite 1 ex.
first Returns the first item in the collection. Calls seq on its argume 2 ex.
rest Returns a possibly empty seq of the items after the first. Calls seq 4 ex.

Maps

Collections / Sequences

Create

Collections / Sequences > Maps

hash-map keyval => key val Returns a new hash map with supplied mappings. 2 ex.
array-map Constructs an array-map. 3 ex.
zipmap Returns a map with the keys mapped to the corresponding vals. 1 ex.
sorted-map keyval => key val Returns a new sorted map with supplied mappings. 1 ex.
sorted-map-by keyval => key val Returns a new sorted map with supplied mappings, 1 ex.
bean Takes a Java object and returns a read-only implementation of the m 1 ex.
frequencies Returns a map from distinct items in coll to the number of times th 1 ex.

Use

Collections / Sequences > Maps

assoc assoc[iate]. When applied to a map, returns a new map of the same 1 ex.
assoc-in Associates a value in a nested associative structure, where ks is a 1 ex.
dissoc dissoc[iate]. Returns a new map of the same (hashed/sorted) type, t 1 ex.
find Returns the map entry for key, or nil if key not present. 2 ex.
key Returns the key of the map entry. 1 ex.
val Returns the value in the map entry. 3 ex.
keys Returns a sequence of the map's keys. 1 ex.
vals Returns a sequence of the map's values. 1 ex.
get Returns the value mapped to key, not-found or nil if key not present. 1 ex.
get-in Returns the value in a nested associative structure, where ks is a 1 ex.
update-in 'Updates' a value in a nested associative structure, where ks is a 3 ex.
select-keys Returns a map containing only those entries in map whose key is in ke 1 ex.
merge Returns a map that consists of the rest of the maps conj-ed onto th 1 ex.
merge-with Returns a map that consists of the rest of the maps conj-ed onto th 3 ex.

Use (Sorted Maps)

Collections / Sequences > Maps

rseq Returns, in constant time, a seq of the items in rev (which can be 1 ex.
subseq sc must be a sorted collection, test(s) one of <, <=, > or >=. Retu 1 ex.
subseq sc must be a sorted collection, test(s) one of <, <=, > or >=. Retu 1 ex.
rsubseq sc must be a sorted collection, test(s) one of <, <=, > or >=. Retu 1 ex.
rsubseq sc must be a sorted collection, test(s) one of <, <=, > or >=. Retu 1 ex.

Sets

Collections / Sequences

Create

Collections / Sequences > Sets

hash-set Returns a new hash set with supplied keys. 1 ex.
set Returns a set of the distinct elements of coll. 2 ex.
sorted-set Returns a new sorted set with supplied keys. 1 ex.
sorted-set-by Returns a new sorted set with supplied keys, using the supplied compa 1 ex.

Use

Collections / Sequences > Sets

conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.
disj disj[oin]. Returns a new set of the same (hashed/sorted) type, that 1 ex.
get Returns the value mapped to key, not-found or nil if key not present. 1 ex.

Structs

Collections / Sequences

Create

Collections / Sequences > Structs

defstruct Same as (def name (create-struct keys...)) 1 ex.
create-struct Returns a structure basis object. 0 ex.
struct Returns a new structmap instance with the keys of the structure-bas 1 ex.
struct-map Returns a new structmap instance with the keys of the structure-bas 1 ex.
accessor Returns a fn that, given an instance of a structmap with the basis, 1 ex.

Use

Collections / Sequences > Structs

get Returns the value mapped to key, not-found or nil if key not present. 1 ex.
assoc assoc[iate]. When applied to a map, returns a new map of the same 1 ex.

Sequences

Collections / Sequences

Create

Collections / Sequences > Sequences

seq Returns a seq on the collection. If the collection is empty, retu 1 ex.
sequence Coerces coll to a (possibly empty) sequence, if it is not already o 1 ex.
repeat Returns a lazy (infinite!, or length n if supplied) sequence of xs. 1 ex.
replicate Returns a lazy seq of n xs. 1 ex.
range Returns a lazy seq of nums from start (inclusive) to end (exclusive 2 ex.
repeatedly Takes a function of no args, presumably with side effects, and retu 2 ex.
iterate Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of 3 ex.
lazy-seq Takes a body of expressions that returns an ISeq or nil, and yields 1 ex.
lazy-cat Expands to code which yields a lazy sequence of the concatenation o 1 ex.
cycle Returns a lazy (infinite!) sequence of repetitions of the items in co 1 ex.
interleave Returns a lazy seq of the first item in each coll, then the second et 3 ex.
interpose Returns a lazy seq of the elements of coll separated by sep 1 ex.
tree-seq Returns a lazy sequence of the nodes in a tree, via a depth-first wal 1 ex.
xml-seq A tree seq on the xml elements as per xml/parse 0 ex.
enumeration-seq Returns a seq on a java.util.Enumeration 0 ex.
iterator-seq Returns a seq on a java.util.Iterator. Note that most collections p 1 ex.
file-seq A tree seq on java.io.Files 1 ex.
line-seq Returns the lines of text from rdr as a lazy sequence of strings. r 2 ex.
resultset-seq Creates and returns a lazy sequence of structmaps corresponding to 0 ex.

Use (General)

Collections / Sequences > Sequences

first Returns the first item in the collection. Calls seq on its argume 2 ex.
second Same as (first (next x)) 1 ex.
last Return the last item in coll, in linear time 2 ex.
rest Returns a possibly empty seq of the items after the first. Calls seq 4 ex.
next Returns a seq of the items after the first. Calls seq on its argume 2 ex.
ffirst Same as (first (first x)) 2 ex.
nfirst Same as (next (first x)) 1 ex.
fnext Same as (first (next x)) 1 ex.
nnext Same as (next (next x)) 1 ex.
nth Returns the value at the index. get returns nil if index out of bou 1 ex.
nthnext Returns the nth next of coll, (seq coll) when n is 0. 1 ex.
rand-nth Return a random element of the (sequential) collection. Will have t 1 ex.
butlast Return a seq of all but the last item in coll, in linear time 2 ex.
take Returns a lazy sequence of the first n items in coll, or all items if 2 ex.
take-last Returns a seq of the last n items in coll. Depending on the type o 1 ex.
take-nth Returns a lazy seq of every nth item in coll. 1 ex.
take-while Returns a lazy sequence of successive items from coll while (pred i 1 ex.
drop Returns a lazy sequence of all but the first n items in coll. 1 ex.
drop-last Return a lazy sequence of all but the last n (default 1) items in col 1 ex.
drop-while Returns a lazy sequence of the items in coll starting from the first 1 ex.
keep Returns a lazy sequence of the non-nil results of (f item). Note, t 3 ex.
keep-indexed Returns a lazy sequence of the non-nil results of (f index item). Not 3 ex.

Use ('Modification')

Collections / Sequences > Sequences

conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.
concat Returns a lazy seq representing the concatenation of the elements in 1 ex.
distinct Returns a lazy sequence of the elements of coll with duplicates remov 2 ex.
group-by Returns a map of the elements of coll keyed by the result of f on e 2 ex.
partition Returns a lazy sequence of lists of n items each, at offsets step a 1 ex.
partition-all Returns a lazy sequence of lists like partition, but may include pa 1 ex.
partition-by Applies f to each value in coll, splitting it each time f returns 2 ex.
split-at Returns a vector of [(take n coll) (drop n coll)] 1 ex.
split-with Returns a vector of [(take-while pred coll) (drop-while pred coll)] 1 ex.
filter Returns a lazy sequence of the items in coll for which (pred item) 1 ex.
remove Returns a lazy sequence of the items in coll for which (pred item) 1 ex.
replace Given a map of replacement pairs and a vector/collection, returns a 2 ex.
shuffle Return a random permutation of coll 1 ex.

Use (Iteration)

Collections / Sequences > Sequences

for List comprehension. Takes a vector of one or more binding-form/col 6 ex.
doseq Repeatedly executes body (presumably for side-effects) with binding 5 ex.
map Returns a lazy sequence consisting of the result of applying f to the 3 ex.
map-indexed Returns a lazy sequence consisting of the result of applying f to 0 1 ex.
mapcat Returns the result of applying concat to the result of applying map 1 ex.
reduce f should be a function of 2 arguments. If val is not supplied, retu 5 ex.
reductions Returns a lazy seq of the intermediate values of the reduction (as 1 ex.
max-key Returns the x for which (k x), a number, is greatest. 1 ex.
min-key Returns the x for which (k x), a number, is least. 2 ex.
doall When lazy sequences are produced via functions that have side effec 1 ex.
dorun When lazy sequences are produced via functions that have side effec 1 ex.

Transients

Collections / Sequences

Create

Collections / Sequences > Transients

transient Alpha - subject to change. Returns a new, transient version of the 2 ex.
persistent! Alpha - subject to change. Returns a new, persistent version of the 1 ex.

Use (General)

Collections / Sequences > Transients

conj! Alpha - subject to change. Adds x to the transient collection, and 1 ex.
pop! Alpha - subject to change. Removes the last item from a transient v 1 ex.
assoc! Alpha - subject to change. When applied to a transient map, adds ma 1 ex.
dissoc! Alpha - subject to change. Returns a transient map that doesn't con 1 ex.
disj! Alpha - subject to change. disj[oin]. Returns a transient set of th 1 ex.

Use ('Modification')

Collections / Sequences > Transients

conj conj[oin]. Returns a new collection with the xs 'added'. (conj ni 1 ex.
concat Returns a lazy seq representing the concatenation of the elements in 1 ex.
distinct Returns a lazy sequence of the elements of coll with duplicates remov 2 ex.
group-by Returns a map of the elements of coll keyed by the result of f on e 2 ex.
partition Returns a lazy sequence of lists of n items each, at offsets step a 1 ex.
partition-all Returns a lazy sequence of lists like partition, but may include pa 1 ex.
partition-by Applies f to each value in coll, splitting it each time f returns 2 ex.
split-at Returns a vector of [(take n coll) (drop n coll)] 1 ex.
split-with Returns a vector of [(take-while pred coll) (drop-while pred coll)] 1 ex.
filter Returns a lazy sequence of the items in coll for which (pred item) 1 ex.
remove Returns a lazy sequence of the items in coll for which (pred item) 1 ex.
replace Given a map of replacement pairs and a vector/collection, returns a 2 ex.
shuffle Return a random permutation of coll 1 ex.

Use (Iteration)

Collections / Sequences > Transients

for List comprehension. Takes a vector of one or more binding-form/col 6 ex.
doseq Repeatedly executes body (presumably for side-effects) with binding 5 ex.
map Returns a lazy sequence consisting of the result of applying f to the 3 ex.
map-indexed Returns a lazy sequence consisting of the result of applying f to 0 1 ex.
mapcat Returns the result of applying concat to the result of applying map 1 ex.
reduce f should be a function of 2 arguments. If val is not supplied, retu 5 ex.
reductions Returns a lazy seq of the intermediate values of the reduction (as 1 ex.
max-key Returns the x for which (k x), a number, is greatest. 1 ex.
min-key Returns the x for which (k x), a number, is least. 2 ex.
doall When lazy sequences are produced via functions that have side effec 1 ex.
dorun When lazy sequences are produced via functions that have side effec 1 ex.

Code Structure

Varibles

Code Structure

Create

Code Structure > Varibles

def Please see http://clojure.org/special_forms#def 4 ex.
defonce defs name to have the root value of the expr iff the named var has no 1 ex.
intern Finds or creates a var named by the symbol name in the namespace ns 1 ex.
declare defs the supplied var names with no bindings, useful for making forwa 1 ex.

Use

Code Structure > Varibles

set! Please see http://clojure.org/special_forms#set 1 ex.
alter-var-root Atomically alters the root binding of var v by applying f to its cu 1 ex.
binding binding => var-symbol init-expr Creates new bindings for the (alre 1 ex.
with-bindings Takes a map of Var/value pairs. Installs for the given Vars the assoc 0 ex.
with-bindings* Takes a map of Var/value pairs. Installs for the given Vars the assoc 0 ex.
with-local-vars varbinding=> symbol init-expr Executes the exprs in a context in w 0 ex.
letfn Takes a vector of function specs and a body, and generates a set of 1 ex.
gensym Returns a new symbol with a unique name. If a prefix string is supp 2 ex.

Inspect

Code Structure > Varibles

var Please see http://clojure.org/special_forms#var 1 ex.
find-var Returns the global var named by the namespace-qualified symbol, or 0 ex.
var-get Gets the value in the var object 0 ex.
var? Returns true if v is of type clojure.lang.Var 1 ex.
bound? Returns true if all of the vars provided as arguments have any bound 1 ex.
resolve same as (ns-resolve *ns* symbol) 1 ex.
ns-resolve Returns the var or Class to which a symbol will be resolved in the 0 ex.
special-symbol? Returns true if s names a special form 0 ex.

Namespaces

Code Structure

Create & Delete

Code Structure > Namespaces

ns Sets *ns* to the namespace named by name (unevaluated), creating it 7 ex.
create-ns Create a new namespace named by the symbol if one doesn't already e 3 ex.
remove-ns Removes the namespace named by the symbol. Use with caution. Cannot 1 ex.

Inspect

Code Structure > Namespaces

*ns* A clojure.lang.Namespace object representing the current namespace. 1 ex.
ns-name Returns the name of the namespace, a symbol. 0 ex.
all-ns Returns a sequence of all namespaces. 1 ex.
the-ns If passed a namespace, returns it. Else, when passed a symbol, retu 1 ex.
find-ns Returns the namespace named by the symbol or nil if it doesn't exist. 1 ex.
ns-publics Returns a map of the public intern mappings for the namespace. 1 ex.
ns-interns Returns a map of the intern mappings for the namespace. 1 ex.
ns-refers Returns a map of the refer mappings for the namespace. 1 ex.
ns-aliases Returns a map of the aliases for the namespace. 0 ex.
ns-imports Returns a map of the import mappings for the namespace. 1 ex.
ns-map Returns a map of all the mappings for the namespace. 1 ex.

Use

Code Structure > Namespaces

in-ns Sets *ns* to the namespace named by the symbol, creating it if needed 2 ex.
ns-resolve Returns the var or Class to which a symbol will be resolved in the 0 ex.
ns-unalias Removes the alias for the symbol from the namespace. 0 ex.
ns-unmap Removes the mappings for the symbol from the namespace. 1 ex.
alias Add an alias in the current namespace to another namespace. Argumen 1 ex.

Misc

Code Structure > Namespaces

namespace-munge Convert a Clojure namespace name to a legal Java package name. 0 ex.
print-namespace-doc Print the documentation string of a Namespace. 0 ex.

Hierarchies

Code Structure

General

Code Structure > Hierarchies

make-hierarchy Creates a hierarchy object for use with derive, isa? etc. 1 ex.
derive Establishes a parent/child relationship between parent and tag. Par 2 ex.
underive Removes a parent/child relationship between parent and tag. h must 1 ex.
parents Returns the immediate parents of tag, either via a Java type inheri 1 ex.
ancestors Returns the immediate and indirect parents of tag, either via a Java 2 ex.
descendants Returns the immediate and indirect children of tag, through a relat 1 ex.
isa? Returns true if (= child parent), or child is directly or indirectly 2 ex.

User Defined Types

Code Structure

General

Code Structure > User Defined Types

defprotocol A protocol is a named set of named methods and their signatures: (d 2 ex.
defrecord Alpha - subject to change (defrecord name [fields*] options* sp 2 ex.
deftype Alpha - subject to change (deftype name [fields*] options* spec 1 ex.
reify reify is a macro with the following structure: (reify options* spec 1 ex.
extend Implementations of protocol methods can be provided using the extend 1 ex.
extend-protocol Useful when you want to provide several implementations of the same 1 ex.
extend-type A macro that expands into an extend call. Useful when you are suppl 1 ex.
extenders Returns a collection of the types explicitly extending protocol 0 ex.

Metadata

Code Structure

General

Code Structure > Metadata

meta Returns the metadata of obj, returns nil if there is no metadata. 1 ex.
with-meta Returns an object of the same type and value as obj, with map m a 1 ex.
vary-meta Returns an object of the same type and value as obj, with (apply f 1 ex.
reset-meta! Atomically resets the metadata for a namespace/var/ref/agent/atom 0 ex.
alter-meta! Atomically sets the metadata for a namespace/var/ref/agent/atom to be 0 ex.

Environment

Require / Import

Environment

General

Environment > Require / Import

use Like 'require, but also refers to each lib's namespace using clojur 3 ex.
require Loads libs, skipping any that are already loaded. Each argument is 4 ex.
import import-list => (package-symbol class-name-symbols*) For each name 2 ex.
refer-clojure Same as (refer 'clojure.core ) 1 ex.
refer refers to all public vars of ns, subject to filters. filters can in 1 ex.

Code

Environment

General

Environment > Code

*compile-files* Set to true when compiling files, false otherwise. 0 ex.
*compile-path* Specifies the directory where 'compile' will write out .class files 0 ex.
*file* The path of the file being evaluated, as a String. Evaluates to ni 0 ex.
*warn-on-reflection* When set to true, the compiler will emit warnings when reflection is 1 ex.
compile Compiles the namespace named by the symbol lib into a set of classf 0 ex.
load Loads Clojure code from resources in classpath. A path is interpreted 1 ex.
load-file Sequentially read and evaluate the set of forms contained in the file 3 ex.
load-reader Sequentially read and evaluate the set of forms contained in the st 0 ex.
load-string Sequentially read and evaluate the set of forms contained in the st 0 ex.
read Reads the next object from stream, which must be an instance of jav 1 ex.
read-string Reads one object from the string s 4 ex.
gen-class When compiling, generates compiled bytecode for a class with the gi 1 ex.
gen-interface When compiling, generates compiled bytecode for an interface with t 0 ex.
loaded-libs Returns a sorted set of symbols naming the currently loaded libs 0 ex.
test test [v] finds fn at key :test in var metadata and calls it, presum 1 ex.

IO

Environment

General

Environment > IO

*in* A java.io.Reader object representing standard input for read operatio 0 ex.
*out* A java.io.Writer object representing standard output for print operat 0 ex.
*err* A java.io.Writer object representing standard error for print operati 0 ex.
print Prints the object(s) to the output stream that is the current value 1 ex.
printf Prints formatted output, as per format 1 ex.
println Same as print followed by (newline) 1 ex.
pr Prints the object(s) to the output stream that is the current value 2 ex.
prn Same as pr followed by (newline). Observes *flush-on-newline* 0 ex.
print-str print to a string, returning it 1 ex.
println-str println to a string, returning it 1 ex.
pr-str pr to a string, returning it 1 ex.
prn-str prn to a string, returning it 1 ex.
newline Writes a newline to the output stream that is the current value of 0 ex.
flush Flushes the output stream that is the current value of *out* 0 ex.
read-line Reads the next line from stream that is the current value of *in* . 1 ex.
slurp Reads the file named by f using the encoding enc into a string and 3 ex.
spit Opposite of slurp. Opens f with writer, writes content, then close 2 ex.
with-in-str Evaluates body in a context in which *in* is bound to a fresh Strin 1 ex.
with-out-str Evaluates exprs in a context in which *out* is bound to a fresh Str 1 ex.
with-open bindings => [name init ...] Evaluates body in a try expression wit 1 ex.

REPL

Environment

General

Environment > REPL

*1 bound in a repl thread to the most recent value printed 1 ex.
*2 bound in a repl thread to the second most recent value printed 1 ex.
*3 bound in a repl thread to the third most recent value printed 2 ex.
*e bound in a repl thread to the most recent exception caught by the rep 1 ex.
*print-dup* When set to logical true, objects will be printed in a way that prese 1 ex.
*print-length* *print-length* controls how many items of each collection the print 1 ex.
*print-level* *print-level* controls how many levels deep the printer will print 0 ex.
*print-meta* If set to logical true, when printing an object, its metadata will al 0 ex.
*print-readably* When set to logical false, strings and characters will be printed wit 0 ex.

Misc

Environment

General

Environment > Misc

*clojure-version* The version info for Clojure core, as a map containing :major :minor 1 ex.
clojure-version Returns clojure version as a printable string. 1 ex.
*command-line-args* A sequence of the supplied command line arguments, or nil if none w 1 ex.
time Evaluates expr and prints the time it took. Returns the value of ex 2 ex.

ClojureDocs(beta)

Table of Contents

Quick Ref for Clojure Core

Arithmetic

Compare

Bitwise Operations

Cast

Test

Create

Use

Test

Create

Use

Cast / Test

Create

Use

Normal

Exceptional

Delay

Function Based

Sequence Based

Laziness

Clojure Types

Java Types

General

Atoms

Refs

Agents

Futures

Thread Local Values

Misc

Create

Call

Test

Create

Inspect and Modify

Create

Use

Arrays

Use

Cast

Create

Misc

Generic Operations

Content Tests

Capabilities

Type Tests

Create

Use

Create

Use

Create

Use

Use (Sorted Maps)

Create

Use

Create

Use

Create

Use (General)

Use ('Modification')

Use (Iteration)

Create

Use (General)

Use ('Modification')

Use (Iteration)

Create

Use

Inspect

Create & Delete

Inspect

Use

Misc

General

General

General

General

General

General

General