53 lines
2.0 KiB
Common Lisp
53 lines
2.0 KiB
Common Lisp
;;; Copyright 2013 Google Inc.
|
|
;;;
|
|
;;; Licensed under the Apache License, Version 2.0 (the "License");
|
|
;;; you may not use this file except in compliance with the License.
|
|
;;; You may obtain a copy of the License at
|
|
;;;
|
|
;;; http://www.apache.org/licenses/LICENSE-2.0
|
|
;;;
|
|
;;; Unless required by applicable law or agreed to in writing, software
|
|
;;; distributed under the License is distributed on an "AS IS" BASIS,
|
|
;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
;;; See the License for the specific language governing permissions and
|
|
;;; limitations under the License.
|
|
|
|
(define-test t-and-nil-are-opposites
|
|
;; NOT is a function which returns the boolean opposite of its argument.
|
|
(true-or-false? ____ (not nil))
|
|
(true-or-false? ____ (not t)))
|
|
|
|
(define-test nil-and-empty-list-are-the-same-thing
|
|
;; In Common Lisp, NIL is also the empty list.
|
|
(true-or-false? ____ '())
|
|
(true-or-false? ____ (not '())))
|
|
|
|
(define-test in-lisp-many-things-are-true
|
|
;; In Common Lisp, the canonical values for truth is T.
|
|
;; However, everything that is non-NIL is true, too.
|
|
(true-or-false? ____ 5)
|
|
(true-or-false? ____ (not 5))
|
|
(true-or-false? ____ "a string")
|
|
;; Even an empty string...
|
|
(true-or-false? ____ "")
|
|
;; ...or a list containing a NIL...
|
|
(true-or-false? ____ (list nil))
|
|
;; ...or an array with no elements...
|
|
(true-or-false? ____ (make-array 0))
|
|
;; ...or the number zero.
|
|
(true-or-false? ____ 0))
|
|
|
|
(define-test and
|
|
;; The logical operator AND can take multiple arguments.
|
|
(true-or-false? ____ (and t t t t t))
|
|
(true-or-false? ____ (and t t nil t t))
|
|
;; If all values passed to AND are true, it returns the last value.
|
|
(assert-equal ____ (and t t t t t 5)))
|
|
|
|
(define-test or
|
|
;; The logical operator OR can also take multiple arguments.
|
|
(true-or-false? ____ (or nil nil nil t nil))
|
|
;; OR returns the first non-NIL value it encounters, or NIL if there are none.
|
|
(assert-equal ____ (or nil nil nil))
|
|
(assert-equal ____ (or 1 2 3 4 5)))
|