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;;; struct.el --- Helpers for working with structs -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;; Version: 0.0.1
;; URL: https://git.wpcarro.dev/wpcarro/briefcase
;; 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:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Dependencies
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(require 'string)
(require 'dash)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Library
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defvar struct--enable-tests? t
"When t, run the test suite defined herein.")
(defmacro struct-update (type field f xs)
"Apply F to FIELD in XS, which is a struct of TYPE.
This is immutable."
(let ((copier (->> type
symbol-name
(string-prepend "copy-")
intern))
(accessor (->> field
symbol-name
(string-prepend (string-concat (symbol-name type) "-"))
intern)))
`(let ((copy (,copier ,xs)))
(setf (,accessor copy) (funcall ,f (,accessor copy)))
copy)))
(defmacro struct-set (type field x xs)
"Immutably set FIELD in XS (struct TYPE) to X."
(let ((copier (->> type
symbol-name
(string-prepend "copy-")
intern))
(accessor (->> field
symbol-name
(string-prepend (string-concat (symbol-name type) "-"))
intern)))
`(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 (->> field
symbol-name
(string-prepend (string-concat (symbol-name type) "-"))
intern)))
`(progn
(setf (,accessor ,xs) ,x)
,xs)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Tests
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(when struct--enable-tests?
(cl-defstruct dummy name age)
(defvar struct--test-dummy (make-dummy :name "Roofus" :age 19))
(struct-set! dummy name "Doofus" struct--test-dummy)
(prelude-assert (string= "Doofus" (dummy-name struct--test-dummy)))
(let ((result (struct-set dummy name "Shoofus" struct--test-dummy)))
;; Test the immutability of `struct-set'
(prelude-assert (string= "Doofus" (dummy-name struct--test-dummy)))
(prelude-assert (string= "Shoofus" (dummy-name result)))))
(provide 'struct)
;;; struct.el ends here
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