Language

Values & Literals

Primary expressions: literals, identifiers, parens, lists, maps, sets

Notch source is built out of expressions, and the smallest expressions are primary expressions: integer literals, boolean literals, string literals, null, identifiers, parenthesized expressions, and the collection literals.

Quick reference

42   0xff   0b101   0o77     # integers (decimal, hex, binary, octal)
true   false                 # booleans
null                         # null
'hello'   "hello"            # strings
[1, 2, 3]                    # list
{'foo' -> 1, 'bar' -> 2}     # map
{1, 2, 3}                    # set
(1 + 2) * 3                  # grouping

Numbers

An integer literal:

Integer literals also accept hexadecimal, binary, and octal prefixes. 0xff, 0b101, and 0o77 are 255, 5, and 63:

0xff
0b101
0o77

Booleans and null

true
false
null

Strings

A string literal is single- or double-quoted:

'hello'
"hello"

Lists

[1, 2, 3]

A trailing comma is allowed:

[1, 2, 3,]

Maps

A map is a brace list of key -> value pairs. Keys are expressions - a bare name is read as a variable, so quote string keys (single- or double-quoted, or the terse : form):

{'foo' -> 1, 'bar' -> 2}
{"foo foo" -> 1, "bar" -> 2}
{:foo123 -> 1, :bar -> 2}

Map values can be any expression, including closures:

{'foo' -> \-> "bar"}

Sets

A brace list without key -> value pairs is a set:

{1, 2, 3}

Identifiers and parentheses

Identifiers refer to bindings in the current scope. Parentheses group expressions:

(1 + 2) * 3