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AllHandlesAreAlreadyTaken's solution

to Sublist in the Common Lisp Track

Published at Feb 25 2020 · 0 comments
Instructions
Test suite
Solution

Given two lists determine if the first list is contained within the second list, if the second list is contained within the first list, if both lists are contained within each other or if none of these are true.

Specifically, a list A is a sublist of list B if by dropping 0 or more elements from the front of B and 0 or more elements from the back of B you get a list that's completely equal to A.

Examples:

  • A = [1, 2, 3], B = [1, 2, 3, 4, 5], A is a sublist of B
  • A = [3, 4, 5], B = [1, 2, 3, 4, 5], A is a sublist of B
  • A = [3, 4], B = [1, 2, 3, 4, 5], A is a sublist of B
  • A = [1, 2, 3], B = [1, 2, 3], A is equal to B
  • A = [1, 2, 3, 4, 5], B = [2, 3, 4], A is a superlist of B
  • A = [1, 2, 4], B = [1, 2, 3, 4, 5], A is not a superlist of, sublist of or equal to B

Setup

Check out Installing Common Lisp for instructions to get started or take a look at the guides available in the track's side bar.

Formatting

While Common Lisp doesn't care about indentation and layout of code, nor whether you use spaces or tabs, this is an important consideration for submissions to exercism.io. Excercism.io's code widget cannot handle mixing of tab and space characters well so using only spaces is recommended to make the code more readable to the human reviewers. Please review your editors settings on how to accomplish this. Below are instructions for popular editors for Common Lisp.

VIM

Use the following commands to ensure VIM uses only spaces for indentation:

:set tabstop=2
:set shiftwidth=2
:set expandtab

(or as a oneliner :set tabstop=2 shiftwidth=2 expandtab). This can be added to your ~/.vimrc file to use it all the time.

Emacs

Emacs is very well suited for editing Common Lisp and has many powerful add-on packages available. The only thing that one needs to do with a stock emacs to make it work well with exercism.io is to evaluate the following code:

(setq-default indent-tabs-mode nil)

This can be placed in your ~/.emacs (or ~/.emacs.d/init.el) in order to have it set whenever Emacs is launched.

One suggested add-on for Emacs and Common Lisp is SLIME which offers tight integration with the REPL; making iterative coding and testing very easy.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

sublist-test.lisp

(ql:quickload "lisp-unit")
#-xlisp-test (load "sublist")

(defpackage #:sublist-test
  (:use #:common-lisp #:lisp-unit))

(in-package #:sublist-test)


;; Equal lists tests:
(define-test empty-lists
  (assert-equal :equal (sublist:sublist (list)
                                         (list))))

(define-test list-equals-itself
  (assert-equal :equal (sublist:sublist (list 1 2 3)
                                         (list 1 2 3))))


;; Unequal lists tests:
(define-test different-lists
  (assert-equal :unequal (sublist:sublist (list 1 2 3)
                                           (list 2 3 4))))

(define-test first-list-missing-element-from-second-list
  (assert-equal :unequal (sublist:sublist (list 1 3)
                                           (list 1 2 3))))

(define-test second-list-missing-element-from-first-list
  (assert-equal :unequal (sublist:sublist (list 1 2 3)
                                           (list 1 3))))

(define-test order-matters-to-a-lists
  (assert-equal :unequal (sublist:sublist (list 1 2 3)
                                           (list 3 2 1))))

(define-test same-digits-different-numbers
  (assert-equal :unequal (sublist:sublist (list 1 0 1)
                                           (list 10 1))))

;; Sublist lists tests:
(define-test empty-list-within-non-empty-list
  (assert-equal :sublist (sublist:sublist (list)
                                           (list 1 2 3))))

(define-test false-start
  (assert-equal :sublist (sublist:sublist (list 1 2 5)
                                           (list 0 1 2 3 1 2 5 6))))

(define-test consecutive
  (assert-equal :sublist (sublist:sublist (list 1 1 2)
                                           (list 0 1 1 1 2 1 2))))

(define-test sublist-at-start
  (assert-equal :sublist (sublist:sublist (list 0 1 2)
                                           (list 0 1 2 3 4 5))))

(define-test sublist-in-middle
  (assert-equal :sublist (sublist:sublist (list 2 3 4)
                                           (list 0 1 2 3 4 5))))

(define-test sublist-at-end
  (assert-equal :sublist (sublist:sublist (list 3 4 5)
                                           (list 0 1 2 3 4 5))))


;; Superlist lists tests:
(define-test not-empty-list-contains-empty-list
  (assert-equal :superlist (sublist:sublist (list 1 2 3)
                                             (list))))

(define-test at-start-of-superlist
  (assert-equal :superlist (sublist:sublist (list 0 1 2 3 4 5)
                                             (list 0 1 2))))

(define-test in-middle-of-superlist
  (assert-equal :superlist (sublist:sublist (list 0 1 2 3 4 5)
                                             (list 2 3))))

(define-test at-end-superlist
  (assert-equal :superlist (sublist:sublist (list 0 1 2 3 4 5)
                                             (list 3 4 5))))

#-xlisp-test
(let ((*print-errors* t)
      (*print-failures* t))
  (run-tests :all))
(defpackage #:sublist
  (:use #:common-lisp)
  (:export #:sublist))

(in-package #:sublist)

(defun sublist (list1 list2)
  "what is list1 of list2 (sublist, superlist, equal or unequal)"
  (cond
    ((equal list1 list2) :equal)
    ((search list2 list1) :superlist)
    ((search list1 list2) :sublist)
    (t :unequal)))

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