Pick random element: Difference between revisions
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x <- runRVar (choice [1 2 3]) DevRandom</lang> |
x <- runRVar (choice [1 2 3]) DevRandom</lang> |
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=={{header|Icon}} and {{header|Unicon}}== |
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The unary operator '?' selects a random element from its argument which may be a string, list, table, or set. |
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<lang Icon>procedure main() |
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L := [1,2,3] # a list |
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x := ?L # random element |
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end</lang> |
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=={{header|Java}}== |
=={{header|Java}}== |
Revision as of 22:52, 9 August 2011
How does one pick a random element from a list?
Haskell
Creating a custom function:
<lang haskell>import Random (randomRIO)
pick :: [a] -> IO a pick xs = randomRIO (0, length xs - 1) >>= return . (xs !!)
x <- pick [1 2 3]</lang>
Using the random-extras library:
<lang haskell>import Data.Random import Data.Random.Source.DevRandom import Data.Random.Extras
x <- runRVar (choice [1 2 3]) DevRandom</lang>
Icon and Unicon
The unary operator '?' selects a random element from its argument which may be a string, list, table, or set.
<lang Icon>procedure main()
L := [1,2,3] # a list x := ?L # random element
end</lang>
Java
<lang java>import java.util.Random; ... int[] array = {1,2,3}; return array[new Random().nextInt(array.length)]; // if done multiple times, the Random object should be re-used</lang>
For a List object rather than an array, substitute list.get(...)
for array[...]
. If preserving the order of the List isn't important, you could call Collections.shuffle(list);
and then list.get(0);
. You would need to shuffle each time unless you remove
d the item from the list.
JavaScript
<lang javascript>var array = [1,2,3]; return array[Math.floor(Math.random() * array.length)];</lang>
PHP
<lang php>$arr = array('foo', 'bar', 'baz'); $x = $arr[array_rand($arr)];</lang>
PicoLisp
<lang PicoLisp>(get Lst (rand 1 (length Lst)))</lang>
Python
<lang python>>>> import random >>> random.choice(['foo', 'bar', 'baz']) 'baz'</lang>
Ruby
<lang ruby>irb(main):001:0> %w(north east south west).sample => "west" irb(main):002:0> (1..100).to_a.sample(2) => [17, 79]</lang>
<lang ruby>irb(main):001:0> %w(north east south west).choice => "south"</lang>
Smalltalk
<lang smalltalk>x := #(1 2 3) atRandom.</lang>