unless

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. Any results are discarded; the unless expression returns Void (zero values).
• A final body expression that already returns Void retains tail position when the unless expression is in tail position, including calls in rec.
• Use when for the negated form.

Example

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