How to resolve the algorithm Search a list step by step in the Common Lisp programming language

Published on 12 May 2024 09:40 PM
#Common lisp

How to resolve the algorithm Search a list step by step in the Common Lisp programming language

Table of Contents

Problem Statement

Find the index of a string (needle) in an indexable, ordered collection of strings (haystack). Raise an exception if the needle is missing. If there is more than one occurrence then return the smallest index to the needle. Return the largest index to a needle that has multiple occurrences in the haystack.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Search a list step by step in the Common Lisp programming language

Source code in the common programming language

(let ((haystack '(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo)))
  (dolist (needle '(Washington Bush))
    (let ((index (position needle haystack)))
      (if index
          (progn (print index) (princ needle))
          (progn (print needle) (princ "is not in haystack"))))))


CL-USER> (defparameter *list* '(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo))
*LIST*
CL-USER> (position 'Bush *list*)
4
CL-USER> (position 'Bush *list* :from-end t)
7
CL-USER> (position 'Washington *list*)
NIL

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