Warning

This was originally written before discovering seq-random-elt.

👃☝ Nose - Picker of Lists

Nose is a small, freshly-shaven yak to grab random elements from a list without invoking either the cl-lib or seq libraries. Why? You're asking the wrong question. Why not? That's an even worse question because I don't have an answer!

API

nose-random-index

Returns a number between 0 and the length of the collection.

Usage

(nose-random-index COLLECTION)

(mapcar #'nose-random-index (make-list 4 (number-sequence 0 9)))
;; => (0 8 9 3), for example

nose-pick

Returns a random element from the collection.

Usage

(nose-pick COLLECTION)

;; Example #1: Pick a number between 1 and 10.

(nose-pick (number-sequence 1 10))
;; 4, for example.

;; Example #2: Polyhedral die roller

(defun d* (sides &optional amount)
  "Return a sequence of die rolls between 1 and SIDES."
  (let ((die (number-sequence 1 sides)))
    (mapcar #'nose-pick (make-list (or amount 1) die))))
;; => d*

(defun d (sides &optional amount)
  "Return the sum of the dice rolled."
  (apply #'+ (d* sides amount)))
;; => d

(d 6 3) ; Roll 3d6, or three six-sided dice and tally the sum.
;; => 13, for example

nose-sample

Returns a sample of elements from a collection. These elements are collected into a list and has a length of the amount given. If amount is nil, only one element is collected.

For collecting a single element, it's better to use nose-pick unless you need it in a list.

Usage

(nose-sample COLLECTION &optional AMOUNT)

;; Let's say I'm some hideous dæmon with three swords that can perform
;; three attacks per round.
;; I wonder who shall fall victim to my thirsty blade...

(let ((party '(fighter thief magic-user dwarf elf)))
  (nose-sample party 3))
;; => (magic-user elf elf), for example

;; Hope you have good evasion saving rolls, puny elf!

nose-sample*

Returns a sample of elements from a collection without replacement. These elements are collected into a list and has a length of the amount given. If amount is nil, only one element is collected.

For collecting a single element, it's better to use nose-pick unless you need it in a list.

Usage

(nose-sample* COLLECTION &optional AMOUNT)

(setq party '(fighter thief magic-user dwarf elf))

;; Sample, but using the whole party.
(nose-sample* '(fighter thief magic-user dwarf elf) 5)
;; => (elf dwarf magic-user fighter thief)
;; Guaranteed no repeats!
;; Well, unless your collection itself has repeats.

(nose-sample* '(fighter thief magic-user dwarf elf) 3)
;; => (fighter magic-user dwarf)

nose-subseq

Returns a subsequence of a collection.

To-Do List

• Optional END argument
• Handle negative arguments

Usage

(nose-subseq COLLECTION START &optional END)

(let ((tens (number-sequence 0 9)))
  (list
   (nose-subseq tens 4)
   (nose-subseq tens 2 8)))
;; => ((4 5 6 7 8 9) (2 3 4 5 6 7))
;; A demonstration of missing END and included END.

nose-remove-nth

Remove the nth element from a collection.

Usage

(nose-remove-nth COLLECTION INDEX)

(let ((not-stooges '(eeny meeny miney curly moe)))
  ;; Uh wait a minute, index 3 doesn't look right!
  (nose-remove-nth not-stooges 3))
;; => (eeny meeny miney moe)

nose-genlist

Generates a list of values returned from a function. Similar to make-list, but for using a function to generate values instead of static ones.

(nose-genlist LENGTH FUNC)

;; Create a list of 6 rolls of 3d6.
(nose-genlist 6 (lambda () (d 6 3)))
;; => eg. (12 14 7 10 15 15)