---
format: "aidr-story-markdown/v1"
id: "1a9292dfd2a6a0036c91b22105c07cf3cb65c3db949723f2647854190694920a"
canonical_url: "https://aidr.today/1a9292df?lang=en"
title: "Lists that keep track of their reversal"
lang: "en"
requested_lang: "en"
available_langs: ["en","vi"]
translation_fallback: null
fallback_fields: []
published_at: "2026-10-01T16:29:04.000Z"
category: "Research"
topics: ["coding"]
source_urls: ["https://grim.cargocut.org/a/rev-list.html","https://lobste.rs/s/eqemtu/lists_keep_track_their_reversal"]
summary: "Summary of a small discussion on how to track, at type level, whether a list is constructed forwards or backwards. It remains to be seen whether this will be useful in everyday life, but the proposal is driven by a specific issue."
---

# Lists that keep track of their reversal

> [Open the canonical story](<https://aidr.today/1a9292df?lang=en>)

**Published:** 2026-10-01T16:29:04.000Z
**Category:** Research
**Topics:** coding

## Summary

Summary of a small discussion on how to track, at type level, whether a list is constructed forwards or backwards\. It remains to be seen whether this will be useful in everyday life, but the proposal is driven by a specific issue\.

## Sources

- [Story source](<https://grim.cargocut.org/a/rev-list.html>)
- [Discussion](<https://lobste.rs/s/eqemtu/lists_keep_track_their_reversal>)