578ed1ba98
Moving all of my Emacs-related files into their own directory at the root of this repository.
80 lines
2.5 KiB
EmacsLisp
80 lines
2.5 KiB
EmacsLisp
;;; cache.el --- Caching things -*- lexical-binding: t -*-
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;; Author: William Carroll <wpcarro@gmail.com>
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;;; Commentary:
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;; An immutable cache data structure.
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;;
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;; This is like a sideways stack, that you can pull values out from and re-push
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;; to the top. It'd be like a stack supporting push, pop, pull.
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;;
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;; This isn't a key-value data-structure like you might expect from a
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;; traditional cache. The name is subject to change, but the underlying idea of
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;; a cache remains the same.
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;;
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;; Think about prescient.el, which uses essentially an LRU cache integrated into
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;; counsel to help create a "clairovoyant", self-organizing list.
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;;
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;; Use-cases:
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;; - Keeps an cache of workspaces sorted as MRU with an LRU eviction strategy.
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;;; Code:
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(require 'prelude)
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(require 'struct)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Library
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(cl-defstruct cache xs)
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;; TODO: Prefer another KBD for yasnippet form completion than company-mode's
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;; current KBD.
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(defun cache/from-list (xs)
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"Turn list, XS, into a cache."
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(make-cache :xs xs))
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(defun cache/contains? (x xs)
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"Return t if X in XS."
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(->> xs
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cache-xs
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(list/contains? x)))
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(defun cache/touch (x xs)
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"Ensure value X in cache, XS, is front of the list.
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If X isn't in XS (using `equal'), insert it at the front."
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(struct/update
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cache
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xs
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(>> (list/reject (lambda (y) (equal x y)))
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(list/cons x))
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xs))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Tests
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(progn
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(let ((cache (cache/from-list '("chicken" "nugget"))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; contains?/2
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(prelude/refute
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(cache/contains? "turkey" cache))
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(prelude/assert
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(cache/contains? "chicken" cache))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; touch/2
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(prelude/assert
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(equal
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(cache/touch "nugget" cache)
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(cache/from-list '("nugget" "chicken"))))
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(prelude/assert
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(equal
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(cache/touch "spicy" cache)
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(cache/from-list '("spicy" "chicken" "nugget"))))))
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(provide 'cache)
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;;; cache.el ends here
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