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