0005183: Array shuffle function in random module

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Date Submitted

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0005183

OCaml

OCaml general

public

2010-11-29 15:03

2011-05-20 14:45

Reporter

warwick

Assigned To

doligez

Priority

normal

Severity

feature

Reproducibility

always

Status

assigned

Resolution

open

Platform

OS Version

Product Version

3.12.0

Target Version

Fixed in Version

Summary

0005183: Array shuffle function in random module

Description

It would be useful to include a function within the Random module to shuffle an array. I think this is a fairly fundamental operation and therefore worthy of inclusion in the OCaml standard library rather than having to download/install an extension module to do it.

It's also a function that's significantly error-prone to implement, so having a correct version in the standard library would be a handy so that individual programmers don't have to code this function from scratch in their applications.

Additional Information

(** [shuffle a] shuffles an array, giving a uniform random distribution *)
let shuffle a =
  for i = pred (Array.length a) downto 1 do
    let j = Random.int (succ i) in
    if i <> j (* faster to omit this test with arrays of about 100000 elements or more *) then (
      let tmp = Array.unsafe_get a i in
      Array.unsafe_set a i (Array.unsafe_get a j);
      Array.unsafe_set a j tmp
    )
  done

Issue History
Date Modified	Username	Field	Change
2010-11-29 15:03	warwick	New Issue
2011-05-20 14:45	doligez	Status	new => assigned
2011-05-20 14:45	doligez	Assigned To	=> doligez

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