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authorVincent Ambo <mail@tazj.in>2021-12-13T22·51+0300
committerVincent Ambo <mail@tazj.in>2021-12-13T23·15+0300
commit019f8fd2113df4c5247c3969c60fd4f0e08f91f7 (patch)
tree76a857f61aa88f62a30e854651e8439db77fd0ea /users/wpcarro/emacs/.emacs.d/wpc/cache.el
parent464bbcb15c09813172c79820bcf526bb10cf4208 (diff)
parent6123e976928ca3d8d93f0b2006b10b5f659eb74d (diff)
subtree(users/wpcarro): docking briefcase at '24f5a642' r/3226
git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c09813172c79820bcf526bb10cf4208
git-subtree-split: 24f5a642af3aa1627bbff977f0a101907a02c69f
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789
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+;;; cache.el --- Caching things -*- 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:
+;; An immutable cache data structure.
+;;
+;; This is like a sideways stack, that you can pull values out from and re-push
+;; to the top.  It'd be like a stack supporting push, pop, pull.
+;;
+;; This isn't a key-value data-structure like you might expect from a
+;; traditional cache.  The name is subject to change, but the underlying idea of
+;; a cache remains the same.
+;;
+;; Think about prescient.el, which uses essentially an LRU cache integrated into
+;; counsel to help create a "clairovoyant", self-organizing list.
+;;
+;; Use-cases:
+;; - Keeps an cache of workspaces sorted as MRU with an LRU eviction strategy.
+
+;;; Code:
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Dependencies
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(require 'prelude)
+(require 'struct)
+(require '>)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Library
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(cl-defstruct cache xs)
+
+;; TODO: Prefer another KBD for yasnippet form completion than company-mode's
+;; current KBD.
+
+(defun cache-from-list (xs)
+  "Turn list, XS, into a cache."
+  (make-cache :xs xs))
+
+(defun cache-contains? (x xs)
+  "Return t if X in XS."
+  (->> xs
+       cache-xs
+       (list-contains? x)))
+
+(defun cache-touch (x xs)
+  "Ensure value X in cache, XS, is front of the list.
+If X isn't in XS (using `equal'), insert it at the front."
+  (struct-update
+   cache
+   xs
+   (>-> (list-reject (lambda (y) (equal x y)))
+       (list-cons x))
+   xs))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Tests
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(progn
+  (let ((cache (cache-from-list '("chicken" "nugget"))))
+    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+    ;; contains?/2
+    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+    (prelude-refute
+     (cache-contains? "turkey" cache))
+    (prelude-assert
+     (cache-contains? "chicken" cache))
+    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+    ;; touch/2
+    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+    (prelude-assert
+     (equal
+      (cache-touch "nugget" cache)
+      (cache-from-list '("nugget" "chicken"))))
+    (prelude-assert
+     (equal
+      (cache-touch "spicy" cache)
+      (cache-from-list '("spicy" "chicken" "nugget"))))))
+
+(provide 'cache)
+;;; cache.el ends here