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home > events > presentation-cfp > default > keyed-patterns-for-guile · Oct 01, 2026

Keyed Patterns for Guile: Map Destructuring After Racket and Clojure

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Keyed Patterns for Guile: Map Destructuring After Racket and Clojure

Table of Contents

A draft for the proposal shelf. Not submitted anywhere. Status: Proposed; the library does not exist yet.

1. Pitch

Racket's match destructures hash tables. Clojure 1.13 hands back what was missing as data. Guile's (ice-9 match) does neither. Build it, and report which choices survive on a Scheme with mutable tables.

2. Abstract

Three Lisps, three answers to one question: what does a function say about the map it is given? Racket's hash* pattern binds by key, takes defaults, binds the rest, and can be closed. Clojure 1.13 adds checked keys and directives that return the selected, excess and missing entries as data, and declines to offer a closed mode. Guile's (ice-9 match) has no hash-table pattern at all, and matches association lists only by position. This paper describes a Guile library that adds keyed patterns over hash tables and association lists, and uses the build to compare the designs: which features depend on persistent maps, which on a macro system, and which are free.

3. Audience, format, venue

Audience
Scheme implementers and users; people who follow pattern matching across the Lisp family.
Format
Scheme Workshop paper with a 20-minute talk; an ELS lightning talk as a first outing.
Where
The Scheme Workshop at ICFP, the European Lisp Symposium. RacketCon only as a comparison talk.

4. What exists and what does not

Run on Racket 8.15, Guile 3.0.10 and Clojure 1.13.0-alpha8 on 2026-10-01:

Feature Clojure 1.13 Racket match Guile (ice-9 match)
Bind by key from a map :keys hash*, hash-table no
Default for an absent key :or #:default no
Absent key is an error :keys! the default: no match no
The unmentioned entries, as data :excess #:rest no
Reject unmentioned entries not offered #:closed no
Absent keys collected as data :missing no no

The comparison is done. The library is not started. It would live as a guile-* project beside the other Guile work.

5. Risks

  • It is a proposal for work, not a report of it. Nothing to submit until the library exists and has tests.
  • SRFI 204 and existing third-party matchers may already cover part of this. Not yet checked; a paper needs that survey first.
  • Clojure 1.13 is alpha. The comparison column must be re-run on the release.

6. Backing

Public repositories:

  • None yet.

Notes on this site: