unlikely is the inverse of likely.

Syntax

(unlikely ⟨predicate⟩)

Semantics

  • unlikely has type (Boolean -> Boolean).
  • It returns the Boolean unchanged.
  • The hint tells the compiler that the condition is expected to be False.
  • The hint is only for optimization; it does not alter semantics.

Example

(if (unlikely failed?)
    recovery
    normal-result)