match

Tests a value against a sequence of patterns, returning the body of the first that matches.

match tests a value against a sequence of patterns, returning the body of the first that matches. It is WCL's primary tool for destructuring unions, optionals, and any shape with multiple cases.

area = match shape {
  Shape::Circle { radius, .. } => pi() * radius * radius,
  Shape::Polygon(n) if n > 2   => 0.0,
  Shape::Empty                 => 0.0,
  _                            => 0.0,
}

See Patterns for the full pattern syntax.

§ 1Guards

An if expr after a pattern adds a runtime test; the arm fires only when both the pattern matches and the guard is true.

classify = match n {
  k if k < 0  => :neg,
  0           => :zero,
  k if k > 10 => :big,
  _           => :small,
}