throw signals an exception value to the nearest enclosing catch that matches it, or invokes the debugger otherwise.

Syntax

(throw ⟨expr⟩)

Semantics

  • The argument must have a known exception type, typically from define-exception.
  • Control transfers out of the current computation until a matching catch handler is found.
  • Exception values can be constructed before they are thrown.
  • throw is not currently polymorphic without an explicit type.

Example

(define (crack egg)
  (match egg
    ((Xenomorph)
     (throw (DeadlyEgg egg)))
    (_ egg)))