subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/emacs/.emacs.d/wpc/random.el

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+;;; random.el --- Functions for working with randomness -*- lexical-binding: t -*-
+
+;; Author: William Carroll <wpcarro@gmail.com>
+;; Version: 0.0.1
+;; Package-Requires: ((emacs "24"))
+;; Homepage: https://user.git.corp.google.com/wpcarro/briefcase
+
+;;; Commentary:
+;; Functions for working with randomness.  Some of this code is not as
+;; functional as I'd like from.
+
+;;; Code:
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Dependencies
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(require 'prelude)
+(require 'number)
+(require 'math)
+(require 'series)
+(require 'list)
+(require 'set)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Library
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun random-int (x)
+  "Return a random integer from 0 to `X'."
+  (random x))
+
+;; TODO: Make this work with sequences instead of lists.
+(defun random-choice (xs)
+  "Return a random element of `XS'."
+  (let ((ct (list-length xs)))
+    (list-get
+     (random-int ct)
+     xs)))
+
+(defun random-boolean? ()
+  "Randonly return t or nil."
+  (random-choice (list t nil)))
+
+;; TODO: This may not work if any of these generate numbers like 0, 1, etc.
+(defun random-uuid ()
+  "Return a generated UUID string."
+  (let ((eight  (number-dec (math-triangle-of-power :base 16 :power 8)))
+        (four   (number-dec (math-triangle-of-power :base 16 :power 4)))
+        (twelve (number-dec (math-triangle-of-power :base 16 :power 12))))
+    (format "%x-%x-%x-%x-%x"
+            (random-int eight)
+            (random-int four)
+            (random-int four)
+            (random-int four)
+            (random-int twelve))))
+
+(defun random-token (length)
+  "Return a randomly generated hexadecimal string of LENGTH."
+  (->> (series/range 0 (number-dec length))
+       (list-map (lambda (_) (format "%x" (random-int 15))))
+       (list-join "")))
+
+;; TODO: Support random-sample
+;; (defun random-sample (n xs)
+;;   "Return a randomly sample of list XS of size N."
+;;   (prelude-assert (and (>= n 0) (< n (list-length xs))))
+;;   (cl-labels ((do-sample
+;;                (n xs y ys)
+;;                (if (= n (set-count ys))
+;;                    (->> ys
+;;                         set-to-list
+;;                         (list-map (lambda (i)
+;;                                     (list-get i xs))))
+;;                  (if (set-contains? y ys)
+;;                      (do-sample n xs (random-int (list-length xs)) ys)
+;;                    (do-sample n xs y (set-add y ys))))))
+;;     (do-sample n xs (random-int (list-length xs)) (set-new))))
+
+(provide 'random)
+;;; random.el ends here