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authorWilliam Carroll <wpcarro@gmail.com>2020-01-30T16·00+0000
committerWilliam Carroll <wpcarro@gmail.com>2020-01-30T16·00+0000
commit578ed1ba98510058cf48f897a9bf4e3391684120 (patch)
tree5eadabd3d232151c75ac2424eaa8771ab25e927e /emacs/.emacs.d/wpc/struct.el
parent3684adf23f847114e1beeaab162398628ba571aa (diff)
Move move .emacs.d out of configs/shared
Moving all of my Emacs-related files into their own directory at the root of
this repository.
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+;;; struct.el --- Helpers for working with structs -*- lexical-binding: t -*-
+;; Author: William Carroll <wpcarro@gmail.com>
+
+;;; 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:
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Wish list
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; - TODO: Replace `symbol-name' and `intern' calls with isomorphism.
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; 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 test-dummy (make-dummy :name "Roofus" :age 19))
+  (struct/set! dummy name "Doofus" test-dummy)
+  (prelude/assert (string= "Doofus" (dummy-name test-dummy)))
+  (let ((result (struct/set dummy name "Shoofus" test-dummy)))
+    ;; Test the immutability of `struct/set'
+    (prelude/assert (string= "Doofus" (dummy-name test-dummy)))
+    (prelude/assert (string= "Shoofus" (dummy-name result)))))
+
+(provide 'struct)
+;;; struct.el ends here