Symmetries in Sorting

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Auteurs principaux: Choudhury, Vikraman, Wong, Wind
Format: Recurso digital
Langue:anglais
Publié: Zenodo 2025
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author Choudhury, Vikraman
Wong, Wind
author_facet Choudhury, Vikraman
Wong, Wind
contents <p>Sorting algorithms are fundamental to computer science, and their correctness criteria are well understood as rearranging elements of a list according to a specified total order on the underlying set of elements. As mathematical functions, they are functions on lists that perform combinatorial operations on the representation of the input list. In this paper, we study sorting algorithms conceptually as abstract sorting functions.<br>There is a canonical surjection from the free monoid on a set (lists of elements) to the free commutative monoid on the same set (multisets of elements). We show that sorting functions determine a section (right inverse) to this surjection satisfying two axioms, that do not presuppose a total order on the underlying set. Then, we establish an equivalence between (decidable) total orders on the underlying set and correct sorting functions.<br>The first part of the paper develops concepts from universal algebra from the point of view of functorial signatures, and gives constructions of free monoids and free commutative monoids in (univalent) type theory. Using these constructions, the second part of the paper develops the axiomatization of sorting functions. The paper uses informal mathematical language, and comes with an accompanying formalisation in Cubical Agda.</p>
format Recurso digital
id zenodo_https___doi_org_10_5281_zenodo_17829282
institution Zenodo
language eng
publishDate 2025
publisher Zenodo
record_format zenodo
spellingShingle Symmetries in Sorting
Choudhury, Vikraman
Wong, Wind
<p>Sorting algorithms are fundamental to computer science, and their correctness criteria are well understood as rearranging elements of a list according to a specified total order on the underlying set of elements. As mathematical functions, they are functions on lists that perform combinatorial operations on the representation of the input list. In this paper, we study sorting algorithms conceptually as abstract sorting functions.<br>There is a canonical surjection from the free monoid on a set (lists of elements) to the free commutative monoid on the same set (multisets of elements). We show that sorting functions determine a section (right inverse) to this surjection satisfying two axioms, that do not presuppose a total order on the underlying set. Then, we establish an equivalence between (decidable) total orders on the underlying set and correct sorting functions.<br>The first part of the paper develops concepts from universal algebra from the point of view of functorial signatures, and gives constructions of free monoids and free commutative monoids in (univalent) type theory. Using these constructions, the second part of the paper develops the axiomatization of sorting functions. The paper uses informal mathematical language, and comes with an accompanying formalisation in Cubical Agda.</p>
title Symmetries in Sorting
url https://doi.org/10.5281/zenodo.17829282