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Extended `extend-protocol`

A Clojure macro to extend a protocol to multiple types with identical implementations

Setup

Leiningen/Boot

[com.sagevisuals/extended-extend-protocol "0"]

Clojure CLI/deps.edn

com.sagevisuals/extended-extend-protocol {:mvn/version "0"}

Require

(require '[extended-extend-protocol.core :refer [multi-extend-protocol]])

Usage

Clojure's extend-protocol doesn't provide a way to avoid repetitive implementations. The singular macro of this library is one way avoid that repetition. Instead of repetitive type+implementation pairs, multi-extend-protocol consumes a series of types sharing a common implementation, followed by the  actual implementation.

Let's pretend we defined OurProtocol to consist of two methods, foo and bar. We supply a series of types followed by the implementation.

(multi-extend-protocol OurProtocol
  AType
  BType
  CClass
  (foo [x] x)
  (bar [y] y))

...expands to...

(extend-protocol OurProtocol
  AType
  (foo [x] x)
  (bar [y] y)
  BType
  (foo [x] x)
  (bar [y] y)
  CClass
  (foo [x] x)
  (bar [y] y))

Investigate weirdness with macroexpand-1.

And note: multi-extend-protocol inherits extend-protocol's pattern of defining methods: (function‑name [args] body), without an explicit fn.

Alternatives

• Clojure's extend function and method maps.

• Write your own little macro.

License

This program and the accompanying materials are made available under the terms of the MIT License.

Copyright © 2024–2025 Brad Losavio.
Compiled by ReadMoi on 2025 December 31.
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