koans, lists

subsist not including right part
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efim 2022-07-25 07:45:38 +00:00
parent fd03924c10
commit ce9c7ac999
1 changed files with 46 additions and 46 deletions

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@ -27,42 +27,42 @@
;; ...or by using the function CONS. ;; ...or by using the function CONS.
(names (cons "Matthew" (cons "Mark" (cons "Margaret" '()))))) (names (cons "Matthew" (cons "Mark" (cons "Margaret" '())))))
;; Try filling in the below blanks in different ways. ;; Try filling in the below blanks in different ways.
(assert-equal ____ fruits) (assert-equal (cons 'orange (cons 'pomello (cons 'clementine nil))) fruits)
(assert-equal ____ some-evens) (assert-equal '(2 . (4 . (6 . nil))) some-evens)
(assert-equal ____ long-numbers) (assert-equal (list 16487302 3826700034 10000000) long-numbers)
(assert-equal ____ names))) (assert-equal '("Matthew" "Mark" "Margaret") names)))
(define-test cons-tructing-lists (define-test cons-tructing-lists
;; The function CONS can be used to add new elements at the beginning of ;; The function CONS can be used to add new elements at the beginning of
;; an existing list. ;; an existing list.
(let ((nums '())) (let ((nums '()))
(setf nums (cons :one nums)) (setf nums (cons :one nums))
(assert-equal ____ nums) (assert-equal '(:one) nums)
(setf nums (cons :two nums)) (setf nums (cons :two nums))
(assert-equal ____ nums) (assert-equal '(:two :one) nums)
;; Lists can contain anything, even objects of different types. ;; Lists can contain anything, even objects of different types.
(setf nums (cons 333 nums)) (setf nums (cons 333 nums))
(assert-equal ____ nums) (assert-equal '(333 :two :one) nums)
;; Lists can contain other lists, too. ;; Lists can contain other lists, too.
(setf nums (cons (list "some" "strings") nums)) (setf nums (cons (list "some" "strings") nums))
(assert-equal ____ nums))) (assert-equal '(("some" "strings") 333 :two :one) nums)))
(define-test car-and-cdr (define-test car-and-cdr
;; We may use functions CAR and CDR (or, alternatively, FIRST and REST) to ;; We may use functions CAR and CDR (or, alternatively, FIRST and REST) to
;; access the two slots of a cons cell. ;; access the two slots of a cons cell.
(let ((x (cons 1 2))) (let ((x (cons 1 2)))
(assert-equal ____ (car x)) (assert-equal 1 (car x))
(assert-equal ____ (cdr x))) (assert-equal 2 (cdr x)))
;; Calls to CAR and CDR are often intertwined to extract data from a nested ;; Calls to CAR and CDR are often intertwined to extract data from a nested
;; cons structure. ;; cons structure.
(let ((structure '((1 2) (("foo" . "bar"))))) (let ((structure '((1 2) (("foo" . "bar")))))
(assert-equal ____ (car structure)) (assert-equal '(1 2) (car structure))
(assert-equal ____ (car (cdr structure))) (assert-equal '(("foo". "bar")) (car (cdr structure)))
(assert-equal ____ (cdr (car (car (cdr structure))))) (assert-equal "bar" (cdr (car (car (cdr structure)))))
;; Lisp defines shorthand functions for up to four such nested calls. ;; Lisp defines shorthand functions for up to four such nested calls.
(assert-equal ____ (car structure)) (assert-equal '(1 2) (car structure))
(assert-equal ____ (cadr structure)) (assert-equal '(("foo" . "bar")) (cadr structure))
(assert-equal ____ (cdaadr structure)))) (assert-equal "bar" (cdaadr structure))))
(define-test push-pop (define-test push-pop
;; PUSH and POP are macros similar to SETF, as both of them operate on places. ;; PUSH and POP are macros similar to SETF, as both of them operate on places.
@ -70,49 +70,49 @@
;; PUSH sets the value of the place to a new cons cell containing some value ;; PUSH sets the value of the place to a new cons cell containing some value
;; in its CAR. ;; in its CAR.
(push 0 place) (push 0 place)
(assert-equal ____ place) (assert-equal '(0 10 20 30 40) place)
;; POP removes a single cons cell from a place, sets the place to its CDR, ;; POP removes a single cons cell from a place, sets the place to its CDR,
;; and returns the value from its CAR. ;; and returns the value from its CAR.
(let ((value (pop place))) (let ((value (pop place)))
(assert-equal ____ value) (assert-equal 0 value)
(assert-equal ____ place)) (assert-equal '(10 20 30 40) place))
;; The return value of POP can be discarded to simply "remove" a single cons ;; The return value of POP can be discarded to simply "remove" a single cons
;; cell from a place. ;; cell from a place.
(pop place) (pop place)
(let ((value (pop place))) (let ((value (pop place)))
(assert-equal ____ value) (assert-equal 20 value)
(assert-equal ____ place)))) (assert-equal '(30 40) place))))
(define-test append-nconc (define-test append-nconc
;; The functions APPEND and NCONC appends one list to the end of another. ;; The functions APPEND and NCONC appends one list to the end of another.
;; While APPEND creates new lists, NCONC modifies existing ones; therefore ;; While APPEND creates new lists, NCONC modifies existing ones; therefore
;; APPEND can be used on literals, but NCONC needs fresh lists. ;; APPEND can be used on literals, but NCONC needs fresh lists.
(assert-equal ____ (append '(:a :b) '(:c))) (assert-equal '(:a :b :c) (append '(:a :b) '(:c)))
(assert-equal ____ (nconc (list :a :b) (list :c))) (assert-equal (list :a :b :c) (nconc (list :a :b) (list :c)))
(let ((list-1 (list 1 2 3)) (let ((list-1 (list 1 2 3))
(list-2 (list 4 5 6))) (list-2 (list 4 5 6)))
;; Both APPEND and NCONC return the appended list, but the interesting part ;; Both APPEND and NCONC return the appended list, but the interesting part
;; is what happens when we try to use the original variables passed to them. ;; is what happens when we try to use the original variables passed to them.
(assert-equal ____ (append list-1 list-2)) (assert-equal (list 1 2 3 4 5 6) (append list-1 list-2))
(assert-equal ____ list-1) (assert-equal (list 1 2 3) list-1)
(assert-equal ____ list-2) (assert-equal (list 4 5 6) list-2)
(assert-equal ____ (nconc list-1 list-2)) (assert-equal (list 1 2 3 4 5 6) (nconc list-1 list-2))
(assert-equal ____ list-1) (assert-equal (list 1 2 3 4 5 6) list-1)
(assert-equal ____ list-2))) (assert-equal (list 4 5 6) list-2)))
(define-test accessing-list-elements (define-test accessing-list-elements
(let ((noms '("peanut" "butter" "and" "jelly"))) (let ((noms '("peanut" "butter" "and" "jelly")))
;; Common Lisp defines accessor functions for lists: FIRST, SECOND, ..., ;; Common Lisp defines accessor functions for lists: FIRST, SECOND, ...,
;; up to TENTH. ;; up to TENTH.
(assert-equal "peanut" (first noms)) (assert-equal "peanut" (first noms))
(assert-equal ____ (second noms)) (assert-equal "butter" (second noms))
(assert-equal ____ (fourth noms)) (assert-equal "jelly" (fourth noms))
;; The function LAST returns the last cons cell of a list. ;; The function LAST returns the last cons cell of a list.
(assert-equal ____ (last noms)) (assert-equal '("jelly") (last noms))
;; The function NTH returns the n-th element of a list. ;; The function NTH returns the n-th element of a list.
(assert-equal "butter" (nth 1 noms)) (assert-equal "butter" (nth 1 noms))
(assert-equal ____ (nth 0 noms)) (assert-equal "peanut" (nth 0 noms))
(assert-equal ____ (nth 3 noms)))) (assert-equal "jelly" (nth 3 noms))))
(define-test cons-tructing-improper-lists (define-test cons-tructing-improper-lists
;; A proper list is a list whose final CDR ends with NIL. ;; A proper list is a list whose final CDR ends with NIL.
@ -122,25 +122,25 @@
(x (list* 1 2 3 4 5)) (x (list* 1 2 3 4 5))
;; ...or pass them as literals via dot notation. ;; ...or pass them as literals via dot notation.
(y '(6 7 8 9 . 0))) (y '(6 7 8 9 . 0)))
(assert-equal ____ (last x)) (assert-equal '(4 . 5) (last x))
(assert-equal ____ (last y))) (assert-equal '(9 . 0) (last y)))
;; We can create a cyclic list by changing the last CDR of a list to refer to ;; We can create a cyclic list by changing the last CDR of a list to refer to
;; another cons cell ;; another cons cell
(let ((list (list 1 2 3 4 5)) (let ((list (list 1 2 3 4 5))
(cyclic-list (list 1 2 3 4 5))) (cyclic-list (list 1 2 3 4 5)))
(setf (cdr (last cyclic-list)) cyclic-list) (setf (cdr (last cyclic-list)) cyclic-list)
;; Function LIST-LENGTH returns NIL if a list is cyclic. ;; Function LIST-LENGTH returns NIL if a list is cyclic.
(assert-equal ____ (list-length list)) (assert-equal 5 (list-length list))
(assert-equal ____ (list-length cyclic-list)) (assert-equal nil (list-length cyclic-list))
;; Many Lisp functions operate only on proper lists. ;; Many Lisp functions operate only on proper lists.
;; The function NTH is not one of them; it can be used to retrieve elements ;; The function NTH is not one of them; it can be used to retrieve elements
;; of cyclic lists. ;; of cyclic lists.
(assert-equal ____ (nth 101 cyclic-list)))) (assert-equal 2 (nth 101 cyclic-list))))
(define-test slicing-lists (define-test slicing-lists
;; The function SUBSEQ returns a subsequence of a list. ;; The function SUBSEQ returns a subsequence of a list.
(let ((noms (list "peanut" "butter" "and" "jelly"))) (let ((noms (list "peanut" "butter" "and" "jelly")))
(assert-equal ____ (subseq noms 0 1)) (assert-equal '("peanut" )(subseq noms 0 1))
(assert-equal ____ (subseq noms 0 2)) (assert-equal '("peanut" "butter" )(subseq noms 0 2))
(assert-equal ____ (subseq noms 2 2)) (assert-equal '() (subseq noms 2 2))
(assert-equal ____ (subseq noms 2)))) (assert-equal '("and" "jelly") (subseq noms 2))))