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Literals and values

This page covers literal forms and direct value constructors accepted by the parser.

Integer literals​

Accepted forms:

42
0
123456

The parser also accepts radix-prefixed integer literals:

0xff
0b101010

These are parsed as integer values.

Floating-point literals​

Accepted form:

3.14
0.5
12.0

Boolean literals​

Accepted forms:

true
false

None literal​

Draton accepts the None literal:

let value = None

Use it where the surrounding type or contract makes the intended optional/nullish shape clear.

String literals​

Basic string literals:

"hello"
"draton"

Interpolated string literals​

Draton supports f-strings:

let name = "Minh"
let greeting = f"Hello {name}"

Interpolation rules, as currently implemented:

  • the outer literal starts with f"
  • literal fragments and embedded expressions can be mixed
  • each { ... } section is parsed as a real expression

Tuple literals​

Accepted forms:

(1, 2)
(1, 2, 3)
()

Parenthesized single expressions stay grouped expressions, not tuples:

(x + 1)

Array literals​

Accepted form:

[1, 2, 3]
[]

Map literals​

Brace literals with key: value entries are maps:

{ "a": 1, "b": 2 }
{}

The empty brace literal is currently parsed as an empty map.

Set literals​

Brace literals without : are sets:

{ 1, 2, 3 }
{ "a", "b" }

Result constructors​

Ok(...) and Err(...) are recognized specially when called with exactly one argument:

Ok(42)
Err("bad input")

Channel type constructor expression​

Draton also parses chan[T] at expression level as a channel constructor/type-form expression:

let jobs = chan[Int]

See Concurrency and channels for the current syntax boundary.