match

match provides structured pattern matching.

Currently:

• match <optional> { None => expr, Some(x) => expr } is supported (expression form),
• match <enum> { E::V => expr, ... } is supported in a restricted exhaustive subset,
• typed-error handling uses a separate match (expr) { ... } statement form (see typed errors).

Full reference: flow match.

Notes#

• Supported forms + tests: flow match

Syntax#

match value {
  Pattern => expr,
  Pattern => expr,
}

Examples#

Example: matching an optional#

fn main () -> int {
  let x: int? = Some(7);
  let y: int = match x {
    None => 5,
    Some(v) => v,
  };
  return y;
}

Example: matching an enum#

enum Msg {
  Quit,
  Add(int),
}

fn main () -> int {
  let m: Msg = Msg::Add(5);
  return match m {
    Msg::Quit => 0,
    Msg::Add(n) => n,
  };
}

See also#

• Full reference: flow match
• Enums: enums
• Typed errors (match statement): typed errors