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learning koans

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- refreshed understanding of lexical vs. dynamic binding
  https://gigamonkeys.com/book/variables.html
- was taught CASE as simpler variant of COND
This commit is contained in:
efim
2022-07-24 13:18:22 +00:00
parent 49c00c24ee
commit fd03924c10
7 changed files with 116 additions and 110 deletions
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34
lisp-koans/koans/nil-false-empty.lisp
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@@ -14,39 +14,39 @@
(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)))
(true-or-false? t (not nil))
(true-or-false? nil (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 '())))
(true-or-false? NIL '())
(true-or-false? t (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")
(true-or-false? t 5)
(true-or-false? nil (not 5))
(true-or-false? t "a string")
;; Even an empty string...
(true-or-false? ____ "")
(true-or-false? t "")
;; ...or a list containing a NIL...
(true-or-false? ____ (list nil))
(true-or-false? t (list nil))
;; ...or an array with no elements...
(true-or-false? ____ (make-array 0))
(true-or-false? t (make-array 0))
;; ...or the number zero.
(true-or-false? ____ 0))
(true-or-false? t 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))
(true-or-false? t (and t t t t t))
(true-or-false? nil (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)))
(assert-equal 5 (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))
(true-or-false? t (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)))
(assert-equal nil (or nil nil nil))
(assert-equal 1 (or 1 2 3 4 5)))