Strings

Strings represent text values. They are declared with double quotes only.

let greeting = "Hello"

Strings can be multiline and preserve line breaks:

let message = "First line
Second line"

Characters

Strings are sequences of characters. You can write characters directly or with escape sequences.

let snow = "Snowman: ☃️"

Mutability

Immutable strings use let, while mutable strings use mutable.

let immutableValue = "You can't change me"
mutable mutableValue = "But you can change me"
TIP

Mutable strings have additional methods and are internally coded as std::String in Rust. Constant strings are treated as &'static str.

Escapes

Use backslashes to escape characters inside a string.

let escaped = "Quote: \" Backslash: \\ Newline:\n Tab:\t Null:\0"
let hex = "Byte: \x41"
let unicode = "Unicode: \u{1F600}"

Supported escape sequences:

  • \\ backslash
  • \" double quote
  • \n newline, \r carriage return, \t tab, \0 null
  • \\xNN two-digit hex byte
  • \\u{...} Unicode code point with 1-6 hex digits
  • {{ and }} to insert braces

Template strings

Strings can interpolate expressions with {}.

let name = "Fa"
let welcome = "Hello {name}"

Use {{ or \{ to insert a literal {, and }} or \} to insert a literal }.

let literal = "Braces: {{ and }}"

Indexing

Strings can be indexed with [] to access a character by position.

let name = "Fa"
let first = name[0]

You can also use ranges and negative indices.

let someString = "hello"
let middle = someString[1..2]
let fromSecond = someString[1..]
let last = someString[-1]

Indexing counts characters, not bytes.

String API

The string API matches the JavaScript String API.

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