2.2 Literal expressions

2.2.1 Numbers

Constants of numeric types are expressed using the conventions and notation of Clojure for floating point values and integers

42
1.2e23
-2.1232E2
0x10   ;; hexadecimal 10 => 16
017    ;; octal 17 => 15
2r101  ;; binary 101 => 3
5r11   ;; base 5 11 => 6
2/3    ;; rational (/ 2 3) => 0.666666666

As seen in the examples, beyond the usual decimal and exponential literals, one can also write literal values using any base between 2 and 32 (with special notation for hexadecimal and octal) and use exact rational numbers, which behave as expected when arithmetically combined:

(+ 1/3 1/6 1/2)  ;; => 1

2.2.2 Strings and booleans

Strings are quoted using " and must be single line ("a string", " another string.").

Booleans have two literal values, true and false .

2.2.3 Lists

Literal lists can be written enclosing a list of space-separated literals in square brackets ([]), e.g.

[0 1 2 3]
["A" -42 true]          ;; lists can be heterogeneous
[["foo" 3] ["bar" 18]]  ;; and nested
[]                      ;; this is the empty list

2.2.4 Sets

Set literals are written by specifiying the literal list of the set’s values, prepended by the symbol #:

#[1 2 3]
#["a" true [1 2] {"a" 3}]
#[a b]

Duplicate values in the list are automatically removed from the resulting set and the order of the elements in the list is irrelevant.

(= #[1 2 3] #[2 1 3]) ;; => true
(= #[1 2 3] #[2 1 3 1 2]) ;; => true

2.2.5 Maps

Map literals are represented by enclosing a sequence of alternating keys and values in braces ({}):

{"key0" 3 "key1" 2}    ;; a map with keys "key0" and "key1"

{"age" 74
 "name" "Alan"
 "scores" [1 0 0 2]                         ;; a map with
 "address" {"street" "sesame" "number" 3}}  ;; nested values

Values in map entries can have any type, and, like keys, can also include non-literal expressions:

(let (size 123
      color "green"
      outer-key "a thing"
      k "key")
  {outer-key {k size (str k 2) color}
   (str outer-key 2) [size color]})
;; => {"a thing" {"key" 123 "key2" "green"}
;;     "a thing2" [123 "green"]}

Although arbitrary expressions are allowed for the keys in map literals, they must eventually evaluate to string values.