Lexical Structure

Comments

// Single-line comment

/* Multi-line
   comment */

Multi-line comments do not nest.

Identifiers

Identifiers start with a letter (a–z, A–Z) or underscore, followed by any combination of letters, digits, or underscores.

identifier := [a-zA-Z_][a-zA-Z0-9_]*

By convention:

• Types, structs, enums, and aspects use PascalCase
• Variables, functions, and fields use snake_case

Keywords

and       as        aspect    break     continue  else      enum
export    false     for       fun       if        impl      import
let       loop      match     mut       or        pub       return
root      self      std       struct    super     true      where
while

Literals

Integers — decimal, with optional _ separators:

42
1_000_000

Floats:

3.14
2.0

Integer and float are distinct types and do not implicitly coerce.

Strings — double-quoted UTF-8:

Sequence	Meaning
\n	Newline
\t	Tab
\\	Backslash
\"	Double quote
\r	Carriage return

String interpolation. A string literal may contain one or more ${expr} placeholders:

let name = "world";
let msg = "hello, ${name}!";       // "hello, world!"
let n = 42;
let s  = "n=${n}";                 // "n=42"

Since*v0.7.0.*

The expression inside ${…} may be any expression whose type implements the Display aspect (i.e. has a .to_string() method). The placeholder desugars to .to_string() concatenated with the surrounding literal fragments using +. String literals may appear inside ${…}:

let x = "${if (true) { "yes" } else { "no" }}";

String concatenation. Two String values may be joined with +:

let full = "hello" + ", " + "world";   // "hello, world"

Since*v0.7.0.*

Booleans: true, false

Absence literal: None

Operators

Category	Operators
Arithmetic	+ - * / %
Compound assign	+= -= *= /= %=
Comparison	== != < <= > >=
Logical	&& || ! (and / or as aliases)
Assignment	=
Error prop	?
Type cast	as
Path	::
Range	.. ..= (for use in for-in only)