tvl-depot/users/wpcarro/emacs/pkgs/struct/struct.el
William Carroll 844cf6a794 refactor(wpcarro/emacs): Remove struct.el dep on s.el
This removes *all* of `struct.el`'s dependencies, which is liberating.

Change-Id: Ic4a2438714ecf547ba5e07a1f0e77d743941073c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6029
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
2022-08-02 20:47:30 +00:00

65 lines
2 KiB
EmacsLisp

;;; struct.el --- Helpers for working with structs -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;; Version: 1.0.0
;; Package-Requires: ((emacs "24.3"))
;;; Commentary:
;; Provides new macros for working with structs. Also provides adapter
;; interfaces to existing struct macros, that should have more intuitive
;; interfaces.
;;
;; Sometimes `setf' just isn't enough.
;;; Code:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Library
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defmacro struct-update (type field f xs)
"Apply F to FIELD in XS, which is a struct of TYPE.
This is immutable."
(let ((copier (struct--copier-for type))
(accessor (struct--accessor-for type field)))
`(let ((copy (,copier ,xs)))
(setf (,accessor copy) (funcall ,f (,accessor copy)))
copy)))
(defmacro struct-update! (type field f xs)
"Mutably apply F to FIELD in XS."
(let ((accessor (struct--accessor-for type field)))
`(progn
(setf (,accessor ,xs) (funcall ,f (,accessor ,xs)))
,xs)))
(defmacro struct-set (type field x xs)
"Immutably set FIELD in XS (struct TYPE) to X."
(let ((copier (struct--copier-for type))
(accessor (struct--accessor-for type field)))
`(let ((copy (,copier ,xs)))
(setf (,accessor copy) ,x)
copy)))
(defmacro struct-set! (type field x xs)
"Set FIELD in XS (struct TYPE) to X mutably.
This is an adapter interface to `setf'."
(let ((accessor (struct--accessor-for type field)))
`(progn
(setf (,accessor ,xs) ,x)
,xs)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Helper Functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun struct--copier-for (type)
(intern (format "copy-%s" (symbol-name type))))
(defun struct--accessor-for (type field)
(intern (format "%s-%s"
(symbol-name type)
(symbol-name field))))
(provide 'struct)
;;; struct.el ends here