{"id":4376,"date":"2026-10-12T09:29:18","date_gmt":"2026-10-12T03:59:18","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=4376"},"modified":"2026-10-12T09:29:18","modified_gmt":"2026-10-12T03:59:18","slug":"run-length-encoding-in-common-lisp","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2026\/10\/12\/run-length-encoding-in-common-lisp\/","title":{"rendered":"Run Length Encoding in Common Lisp"},"content":{"rendered":"

I was curious to generate Common Lisp<\/strong><\/em> code using ChatGPT<\/strong><\/em> and Claude<\/strong><\/em> for a simple problem and then compare the code. After thinking for while, I decided to use the \u201cRun Length Encoding\u201d<\/strong><\/em> problem for this experiment.<\/p>\n

Here is the prompt I used:<\/p>\n

\u201cYou are an experienced Common Lisp developer. Please write bug-free and elegant Lisp code for run-length encoding\/decoding.\u201d\u00a0<\/span><\/strong><\/em><\/p>\n

Nothing fancy. To the point.<\/p>\n

Here is the code generated by ChatGPT<\/strong><\/em> (model: GPT 5.6 Medium mode):<\/p>\n

\"ChatGPT<\/a>
ChatGPT Code<\/strong><\/figcaption><\/figure>\n

The following was generated by Claude<\/strong><\/em> (model: Opus 5.5 Medium mode):<\/p>\n

\"Claude<\/a>
Claude Code<\/strong><\/figcaption><\/figure>\n

You can see that ChapGPT\u2019s<\/strong><\/em> code for encoding is slightly more verbose<\/span> than Claude\u2019s<\/strong><\/em>, but the decoding implementation is more compact. Such differences are expected even among human programmers, so no big deal. But what made me happy is the fact that both implementations worked the first time, without bugs! I think simplicity of the problem is the main reason for this.\u00a0<\/span><\/p>\n

Here is the output for different inputs:<\/p>\n

\"Program<\/a>
Program Output<\/strong><\/figcaption><\/figure>\n

I tested the programs in LispWorks Lisp ver 8.0<\/strong><\/em>. You can download the source here<\/span><\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

I was curious to generate Common Lisp code using ChatGPT and Claude for a simple problem and then compare the code. After thinking for while, I decided to use the \u201cRun Length Encoding\u201d problem for this experiment. Here is the prompt I used: \u201cYou are an experienced Common Lisp developer. Please write bug-free and elegant […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[18,17],"tags":[348,454,465],"class_list":["post-4376","post","type-post","status-publish","format-standard","hentry","category-lisp","category-programming","tag-chatgpt","tag-claude","tag-run-length-encoding"],"jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-18A","jetpack-related-posts":[{"id":2927,"url":"https:\/\/www.rangakrish.com\/index.php\/2022\/10\/20\/why-learn-lisp\/","url_meta":{"origin":4376,"position":0},"title":"Why Learn Lisp?","author":"admin","date":"October 20, 2022","format":false,"excerpt":"In the last article, I had shared my views on why programmers should learn Prolog, preferably as the first language. What language should one learn next? I strongly pitch for Lisp, to be precise, \u201cCommon Lisp\u201d. Lisp happens to be the second oldest (1958) programming language, only after Fortran (1957)!\u2026","rel":"","context":"In "LISP"","block_context":{"text":"LISP","link":"https:\/\/www.rangakrish.com\/index.php\/category\/lisp\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":3589,"url":"https:\/\/www.rangakrish.com\/index.php\/2025\/01\/04\/word-transformation-puzzle-part-2-implementation-in-common-lisp\/","url_meta":{"origin":4376,"position":1},"title":"Word Transformation Puzzle – Part 2: Implementation in Common Lisp","author":"admin","date":"January 4, 2025","format":false,"excerpt":"In the last article\u00a0I discussed an interesting word puzzle and showed how to solve it using Prolog. Here is the problem statement: \u201cYou are given two words of the same length. 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It has been around for over 25 years\u2026","rel":"","context":"In "LISP"","block_context":{"text":"LISP","link":"https:\/\/www.rangakrish.com\/index.php\/category\/lisp\/"},"img":{"alt_text":"The Lisp Code","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/04\/LispCode-300x168.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/04\/LispCode-300x168.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/04\/LispCode-300x168.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":3525,"url":"https:\/\/www.rangakrish.com\/index.php\/2024\/10\/13\/using-chatgpt-for-algorithmic-music-composition\/","url_meta":{"origin":4376,"position":3},"title":"Using ChatGPT for Algorithmic Music Composition","author":"admin","date":"October 13, 2024","format":false,"excerpt":"Algorithmic music composition is one of my favourite areas. 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