{"id":3199,"date":"2023-09-04T09:01:10","date_gmt":"2023-09-04T03:31:10","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=3199"},"modified":"2023-09-04T09:04:20","modified_gmt":"2023-09-04T03:34:20","slug":"simulating-python-zip-in-lisp","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2023\/09\/04\/simulating-python-zip-in-lisp\/","title":{"rendered":"Simulating Python Zip in Lisp"},"content":{"rendered":"

The zip()<\/strong><\/em> function in Python<\/strong><\/em><\/a> is a convenient mechanism for iterating over multiple \u201citerables\u201d<\/strong><\/em> in parallel. Looping over lists is a common scenario.<\/p>\n

\"Python<\/a>
Python Zip() Feature<\/strong><\/figcaption><\/figure>\n

Here is the output generated by the above code:<\/p>\n

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

Common Lisp<\/strong><\/em> does not have such a feature built into the language or as part of the standard library. Of course, we have the expressive \u201cloop\u201d<\/strong> <\/em>construct that allows us to iterate over multiple lists, etc. Here is an example that traverses multiple lists:<\/p>\n

\"Common<\/a>
Common Lisp Loop Function<\/strong><\/figcaption><\/figure>\n

It is not difficult to program the zip()<\/strong> <\/em>functionality in Lisp<\/strong><\/em>. In this article, I will show two ways to do this. For the sake of brevity, I am going to focus on lists<\/strong><\/em> as arguments to zip()<\/strong><\/em>.<\/p>\n

Using Function Closure<\/h3>\n

Our first implementation takes advantage of Lisp<\/strong><\/em>\u2019s \u201cclosure\u201d<\/strong><\/em>, where we return an anonymous function from a function. The anonymous function stores its state in the enclosing function\u2019s variables. Here is the code:<\/p>\n

\"Closure-based<\/a>
Closure-based Implementation<\/strong><\/figcaption><\/figure>\n

The zip()<\/strong><\/em> function takes multiple lists as its arguments and returns a function that captures this state. Every time this function is called, it will return the next sequence from the list. For convenience and readability, I have also defined the next()<\/strong><\/em> function (as a macro) that returns the next element. It returns \u201cnil\u201d<\/strong><\/em> when the entire collection has been traversed.<\/p>\n

The following shows an interactive session that uses the zip()<\/strong><\/em> function:<\/p>\n

\"Using<\/a>
Using Closure-based Implementation<\/strong><\/figcaption><\/figure>\n

Note that the function correctly handles the case when not all lists are of the same size.<\/p>\n

Using \u201cstruct\u201d Abstraction<\/h3>\n

Yet another (in my view, better) approach is to wrap the zip()<\/strong> <\/em>functionality around a class\/struct. I have chosen struct<\/strong> <\/em>because that is sufficient for our case. Here is the code:<\/p>\n

\"Using<\/a>
Using Defstruct<\/strong><\/figcaption><\/figure>\n

Our struct<\/strong><\/em> contains just one instance variable called \u201celements<\/strong><\/em>\u201d to keep track of the supplied collection. The main zip()<\/strong><\/em> method calls the constructor to instantiate a new object. As earlier, the next()<\/strong><\/em> method returns the next set of elements and return \u201cnil\u201d<\/strong><\/em> when the collection is fully traversed. I have also defined two convenience methods size()<\/strong> <\/em>and remaining()<\/strong><\/em>. The former returns the number of pending items and the latter returns all remaining items from the sequence.<\/p>\n

The following shows its usage:<\/p>\n

\"Using<\/a>
Using Defstruct Version<\/strong><\/figcaption><\/figure>\n

It is possible to extend the implementation to cover other collections such as arrays, dictionaries, etc.<\/p>\n

I have tested this implementation in LispWorks Enterprise<\/a> 8.0.1, 64 bit<\/strong><\/em> edition on Windows 10<\/strong><\/em>. Here is the source code<\/strong><\/em><\/a>.<\/p>\n

Have a nice week!<\/p>\n","protected":false},"excerpt":{"rendered":"

The zip() function in Python is a convenient mechanism for iterating over multiple \u201citerables\u201d in parallel. Looping over lists is a common scenario. Here is the output generated by the above code: Common Lisp does not have such a feature built into the language or as part of the standard library. Of course, we have […]<\/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_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_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}},"categories":[18,17,103],"tags":[110,208,367],"class_list":["post-3199","post","type-post","status-publish","format-standard","hentry","category-lisp","category-programming","category-python","tag-common-lisp","tag-python","tag-zip"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-PB","jetpack-related-posts":[{"id":3312,"url":"https:\/\/www.rangakrish.com\/index.php\/2024\/01\/28\/the-hy-programming-language\/","url_meta":{"origin":3199,"position":0},"title":"The Hy Programming Language","author":"admin","date":"January 28, 2024","format":false,"excerpt":"In an earlier article\u00a0I had explained how to execute Python code from within Common Lisp using \u201cCLPython\u201d package. In contrast to that approach, \u201cHy\u201d\u00a0is a Lisp-style language (not compatible with Common Lisp) that is embedded in Python and hence provides seamless interoperability with Python code. Installation is straightforward (it is\u2026","rel":"","context":"In "Hy Language"","block_context":{"text":"Hy Language","link":"https:\/\/www.rangakrish.com\/index.php\/category\/hy-language\/"},"img":{"alt_text":"Hy REPL","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2024\/01\/console-300x148.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":558,"url":"https:\/\/www.rangakrish.com\/index.php\/2017\/07\/07\/clpython-python-in-common-lisp\/","url_meta":{"origin":3199,"position":1},"title":"CLPython – Python in Common Lisp","author":"admin","date":"July 7, 2017","format":false,"excerpt":"My work in the area of NLP requires\u00a0me to work with several frameworks across multiple languages such as Java, Python and Lisp. Sometime ago I got a chance to experiment with CLPython, an open-source implementation of Python in Common Lisp. Although CLPython is not under active development now, I found\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":567,"url":"https:\/\/www.rangakrish.com\/index.php\/2017\/07\/22\/clpython-python-in-common-lisp-part-2\/","url_meta":{"origin":3199,"position":2},"title":"CLPython: Python in Common Lisp – Part 2","author":"admin","date":"July 22, 2017","format":false,"excerpt":"We looked at the basic features of CLPython\u00a0in our last blog. In today's post let us look at the support for Python classes. PYTEST 130 > (defun pyclass () \u00a0 (run\u00a0 \"class Employee: \u00a0\u00a0 def __init__(self, name, dept): \u00a0\u00a0 \u00a0 self.name = name \u00a0\u00a0 \u00a0 self.dept = dept \u00a0\u00a0 def\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":1560,"url":"https:\/\/www.rangakrish.com\/index.php\/2019\/05\/05\/python-integration-in-mathematica-12\/","url_meta":{"origin":3199,"position":3},"title":"Python Integration in Mathematica 12","author":"admin","date":"May 5, 2019","format":false,"excerpt":"Mathematica has had Python support since ver 11.2 through ExternalEvaluate[]. In ver 11.3 it was possible to input Python expression in a cell by beginning with \u201c>\u201d character. The good news is that Mathematica 12 has significantly enhanced this integration. Python Cells Let us start with the simplest way to\u2026","rel":"","context":"In "Mathematica"","block_context":{"text":"Mathematica","link":"https:\/\/www.rangakrish.com\/index.php\/category\/mathematica\/"},"img":{"alt_text":"Function References","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2019\/05\/External-Evaluate-4.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2019\/05\/External-Evaluate-4.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2019\/05\/External-Evaluate-4.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":3399,"url":"https:\/\/www.rangakrish.com\/index.php\/2024\/06\/08\/kp-astrology-rest-server-part-2\/","url_meta":{"origin":3199,"position":4},"title":"KP Astrology REST Server: Part 2","author":"admin","date":"June 8, 2024","format":false,"excerpt":"In my earlier article, I had briefly described the REST server I wanted to build for Krishnamurti Padhdhati system of astrology. After a long time I have managed to complete the implementation and it is now ready for deployment. In this article, I will go over some of its features\u2026","rel":"","context":"In "Astrology"","block_context":{"text":"Astrology","link":"https:\/\/www.rangakrish.com\/index.php\/category\/astrology\/"},"img":{"alt_text":"KPRest Application Window","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2024\/06\/Start-300x174.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":3350,"url":"https:\/\/www.rangakrish.com\/index.php\/2024\/03\/09\/the-hy-programming-language-part-2\/","url_meta":{"origin":3199,"position":5},"title":"The Hy Programming Language – Part 2","author":"admin","date":"March 9, 2024","format":false,"excerpt":"I wrote about \u201cHy\u201d language in an earlier article. 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It is taken from\u2026","rel":"","context":"In "Hy Language"","block_context":{"text":"Hy Language","link":"https:\/\/www.rangakrish.com\/index.php\/category\/hy-language\/"},"img":{"alt_text":"Inheritance Example","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2024\/03\/Inheritance-Example-201x300.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2024\/03\/Inheritance-Example-201x300.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2024\/03\/Inheritance-Example-201x300.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/3199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/comments?post=3199"}],"version-history":[{"count":0,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/3199\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/media?parent=3199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/categories?post=3199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/tags?post=3199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}