Add `:key` for `extrema`
author |
Steve Losh <steve@stevelosh.com> |
date |
Thu, 05 Dec 2019 19:41:57 -0500 |
parents |
de9d10a9b4b5 |
children |
(none) |
(in-package :losh.random)
(defun-inline epsilon (val)
(etypecase val
(integer 1)
(short-float short-float-epsilon)
(long-float long-float-epsilon)
(single-float single-float-epsilon)
(double-float double-float-epsilon)))
(defun-inlineable randomp (&optional (chance 0.5) (generator #'random))
"Return a random boolean with `chance` probability of `t`."
(< (funcall generator 1.0) chance))
(defun random-elt (seq &optional (generator #'random))
"Return a random element of `seq`, and whether one was available.
This will NOT be efficient for lists.
Examples:
(random-elt #(1 2 3))
=> 1
T
(random-elt nil)
=> nil
nil
"
(let ((length (length seq)))
(if (zerop length)
(values nil nil)
(values (elt seq (funcall generator length)) t))))
(defun-inlineable random-range (min max &optional (generator #'random))
"Return a random number in [`min`, `max`)."
(+ min (funcall generator (- max min))))
(defun-inlineable random-range-inclusive (min max &optional (generator #'random))
"Return a random number in [`min`, `max`]."
(+ min (funcall generator (+ (- max min) (epsilon min)))))
(defun-inlineable random-range-exclusive (min max &optional (generator #'random))
"Return a random number in (`min`, `max`)."
(+ (epsilon min) min (funcall generator (- max min (epsilon min)))))
(defun-inlineable random-around (value spread &optional (generator #'random))
"Return a random number within `spread` of `value` (inclusive)."
(random-range-inclusive (- value spread)
(+ value spread)
generator))
(let (spare)
(defun clear-gaussian-spare ()
(setf spare nil))
(defun random-gaussian (mean standard-deviation &optional (generator #'random))
"Return a random float from a gaussian distribution. NOT THREAD-SAFE (yet)!"
;; https://en.wikipedia.org/wiki/Marsaglia_polar_method
(declare (optimize (speed 3))
(inline random-range))
(let ((mean (coerce mean 'single-float))
(standard-deviation (coerce standard-deviation 'single-float)))
(flet ((scale (n)
(+ mean (* n standard-deviation))))
(if spare
(prog1
(scale (the single-float spare))
(setf spare nil))
(loop
:for u :of-type single-float = (+ -1.0 (the single-float (funcall generator 2.0)))
:for v :of-type single-float = (+ -1.0 (the single-float (funcall generator 2.0)))
:for s :of-type single-float = (+ (square u) (square v))
:while (or (>= s 1.0) (= s 0.0))
:finally
(setf s (sqrt (/ (* -2.0 (the (single-float * (0.0)) (log s)))
s))
spare (* v s))
(return (scale (* u s)))))))))
(defun random-gaussian-integer (mean standard-deviation &optional (generator #'random))
"Return a random integer from a gaussian distribution. NOT THREAD-SAFE (yet)!"
(values (round (random-gaussian mean standard-deviation generator))))
(defun d (n sides &optional (plus 0))
"Roll some dice.
Examples:
(d 1 4) ; rolls 1d4
(d 2 8) ; rolls 2d8
(d 1 10 -1) ; rolls 1d10-1
"
(+ (iterate (repeat n)
(sum (1+ (random sides))))
plus))