6b456c1b7a
Currently paying the price of months of non-diligent git usage. Here's what has changed. - Theming support in Gvcci and wpgtk - Dropping support for i3 - Supporting EXWM - Many Elisp modules - Collapsed redundant directories in ./configs
66 lines
1.9 KiB
EmacsLisp
66 lines
1.9 KiB
EmacsLisp
;;; bag.el --- Working with bags (aka multi-sets) -*- lexical-binding: t -*-
|
|
;; Author: William Carroll <wpcarro@gmail.com>
|
|
|
|
;;; Commentary:
|
|
;; What is a bag? A bag should be thought of as a frequency table. It's a way
|
|
;; to convert a list of something into a set that allows duplicates. Isn't
|
|
;; allowing duplicates the whole thing with Sets? Kind of. But the interface
|
|
;; of Sets is something that bags resemble, so multi-set isn't as bag of a name
|
|
;; as it may first seem.
|
|
;;
|
|
;; If you've used Python's collections.Counter, the concept of a bag should be
|
|
;; familiar already.
|
|
;;
|
|
;; Interface:
|
|
;; - add :: x -> Bag(x) -> Bag(x)
|
|
;; - remove :: x -> Bag(x) -> Bag(x)
|
|
;; - union :: Bag(x) -> Bag(x) -> Bag(x)
|
|
;; - difference :: Bag(x) -> Bag(x) -> Bag(x)
|
|
|
|
;;; Code:
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;; Dependencies
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
(require 'number)
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;; Library
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
(cl-defstruct bag xs)
|
|
|
|
(defun bag/update (f xs)
|
|
"Call F on alist in XS."
|
|
(let ((ys (bag-xs xs)))
|
|
(setf (bag-xs xs) (funcall f ys))))
|
|
|
|
(defun bag/new ()
|
|
"Create an empty bag."
|
|
(make-bag :xs (alist/new)))
|
|
|
|
(defun bag/contains? (x xs)
|
|
"Return t if XS has X."
|
|
(alist/has-key? x (bag-xs xs)))
|
|
|
|
;; TODO: Tabling this for now since working with structs seems to be
|
|
;; disappointingly difficult. Where is `struct/update'?
|
|
;; (defun bag/add (x xs)
|
|
;; "Add X to XS.")
|
|
|
|
;; TODO: What do we name delete vs. remove?
|
|
;; (defun bag/remove (x xs)
|
|
;; "Remove X from XS.
|
|
;; This is a no-op is X doesn't exist in XS.")
|
|
|
|
(defun bag/from-list (xs)
|
|
"Map a list of `XS' into a bag."
|
|
(->> xs
|
|
(list/reduce
|
|
(bag/new)
|
|
(lambda (x acc)
|
|
(bag/add x 1 #'number/inc acc)))))
|
|
|
|
(provide 'bag)
|
|
;;; bag.el ends here
|