t3x.org / sketchy / library / booleanp.html
SketchyLISP
Reference
  Copyright (C) 2007
Nils M Holm

boolean?

Conformance: R5RS Scheme

Purpose: Check whether a datum is a truth value.

Arguments:
X - datum

Implementation:

(define (boolean? x)
  (or (eq? x #t)
      (eq? x #f)))

Example:

(boolean? #f) 
=> #t

See also:
list?, null?.