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paul-jewell's solution

to Anagram in the Common Lisp Track

Published at Mar 28 2020 · 0 comments
Instructions
Test suite
Solution

Given a word and a list of possible anagrams, select the correct sublist.

Given "listen" and a list of candidates like "enlists" "google" "inlets" "banana" the program should return a list containing "inlets".

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

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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.

Source

Inspired by the Extreme Startup game https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

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

anagram-test.lisp

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

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

(in-package #:anagram-test)

(define-test no-matches
  (assert-equal '()
      (anagram:anagrams-for
       "diaper"
       '("hello" "world" "zombies" "pants"))))

(define-test detect-simple-anagram
  (assert-equal '("tan")
      (anagram:anagrams-for "ant" '("tan" "stand" "at"))))

(define-test does-not-confuse-different-duplicates
  (assert-equal '() (anagram:anagrams-for "galea" '("eagle"))))

(define-test eliminate-anagram-subsets
  (assert-equal '() (anagram:anagrams-for "good" '("dog" "goody"))))

(define-test detect-anagram
  (assert-equal '("inlets")
      (anagram:anagrams-for
       "listen"
       '("enlists" "google" "inlets" "banana"))))

(define-test multiple-anagrams
  (assert-equal '("gallery" "regally" "largely")
      (anagram:anagrams-for
       "allergy"
       '("gallery" "ballerina" "regally" "clergy" "largely" "leading"))))

(define-test case-insensitive-anagrams
  (assert-equal '("Carthorse")
      (anagram:anagrams-for
       "Orchestra"
       '("cashregister" "Carthorse" "radishes"))))

(define-test word-is-not-own-anagram
  (assert-equal '()
      (anagram:anagrams-for "banana" '("banana"))))

(define-test word-is-not-own-anagram-case-insensitively
  (assert-equal '()
      (anagram:anagrams-for "bananarama" '("BananaRama"))))

#-xlisp-test
(let ((*print-errors* t)
      (*print-failures* t))
  (run-tests :all :anagram-test))
(in-package #:cl-user)
(defpackage #:anagram
  (:use #:common-lisp)
  (:export #:anagrams-for))

(in-package #:anagram)

(defun ordered (word)
  (sort (copy-seq word) 'char-lessp))

(defun anagrams-for (word candidates)
  (labels (
           (anagram-p (candidate)
             (and (not (string-equal word candidate))
                  (string-equal (ordered word) (ordered candidate)))))
    (remove-if-not #'anagram-p candidates)))

Community comments

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paul-jewell's Reflection

Two versions - the third iteration has the predicate function local to the anagrams-for function.