unless is the negated counterpart to when.

Syntax

(unless ⟨test⟩
  ⟨expr⟩...)

Semantics

  • unless is a convenience form for one-sided conditional code for effect.
  • Expressions in the body are sequenced as an implicit progn, and the result must unify to Void.
  • Use when for the negated form.

Example

(unless ready?
  (error "Not ready"))