Topic awaiting preservation: An elegant way to mix arrays arrays... (Page 1 of 1)

Hi !

I am looking for an elegant way to mix arrays arrays.

I admit i am fairly proud to have found the hereunder script. Unfortunately,
it breaks the lines.

Thanx for your help !

array=[

['Bernard','Bernard'],

['Jean','Jean'],

['Jocelyne','Jocelyne'],

['Maud','Maud'],

['Rudolf','Rudolf']

]



function aleate()

{

return Math.pow(-1, Math.round(2*Math.random()))

}



alert(array.sort(aleate))

Grand Mamamouchi: Hello and welcome in the Asylum.

What do you mean by "it breaks the lines" ? If you mean that the content of the array appear on a straight line with the alert( ), it is 100% normal. That is the way arrays are displayed in an alert( ). To prove that, simply put an alert( array ) before using the alert(array.sort(aleate)). If you want a pretty display, you'll need few lines of code for that, to browse each member of the Array and add a LF character.

Oh, and you could shorten your aleate( ) function. All it needs to do is to return a positive or negative number at random. For the record, I've included a dump( ) method on the Array object, which gives the following script:

array =

[

	"toto",

	78,

	['Bernard','Bernard'],

	['Jean','Jean'],

	['Jocelyne','Jocelyne'],

	['Maud','Maud'],

	['Rudolf','Rudolf']

]



Array.prototype.dump = function( indent )

{

	var bla = ""

	if( !indent )

		indent = ""

	for( var i in this )

	{

		var typeOf = typeof( this[ i ] )

		if( typeOf!="function" )

		{

			bla += indent+ i +" -{"

			if( this[i].dump )

				bla +="array}->\n"+ indent +"{\n"+ this[i].dump( indent+"\t" )+ indent +"}\n"

			else

				 bla += typeOf +"}-> "+ this[i] +"\n"

		}

	}

	return bla

}



function aleate()

{

	return 2*Math.random()-1

}



alert( array.sort(aleate).dump() )

As a side note, what's the point of the random sort? Wouldn't it be better to do an O(n) permutation if randomness is needed? Besides, I think it's important for a sort function that the comparison returns the same value when called on the same elements more than once; you might not be getting an even distribution.


 

If the only problem is the presentation,

alert(array.sort(aleate).join('\n'));

But I've seen this question asked in codingforums, webxpertz, sitepoint, webdeveloper forums and here. I've not seen any reply by the original poster anywhere.

--
var Liorean = {
prototype: XHTMLGuru.prototype,
abode: "http://codingforums.com/",
profile: "http://codingforums.com/member.php?u=5798"};

lioran: it's always a pleasure to see a dead simple solution doing what I spent 19 lines to do

Slime: Indeed O(n) is better.

Array.prototype.shuffle = function()

{

	for( var i=1; i<this.length; i++ )

		if( 2*Math.random()>1 )

		{

			var tmp = this[i]

			this[i] = this[i-1]

			this[i-1] = tmp

		}

	return this

}

the random function could be improved to get a better distribution ( gaussian, poisson, perlin ... )

Poi:That's probably a lot more effective than my solution...

Array.prototype.shuffle=function(){

    var

        l=this.length,

        a=[];

    while(l-->0)

        a.push(this.splice(Math.floor(l*Math.random()),1));

    return this.concat(a);

}

--
var Liorean = {
abode: "http://codingforums.com/",
profile: "http://codingforums.com/member.php?u=5798"};

the previous function was not random enough :

Array.prototype.shuffle = function()

{

	var

		L = this.length,

		random



	while( --L )

		if( L-(random = Math.round(L*Math.random())) )

		{

			var tmp = this[L]

			this[L] = this[random]

			this[random] = tmp

		}



	return this

}

To get a "random" function that shuffles the array the same way, we could use pseudo-random number generator and generate a seed ( eventually based on a hash key made from the datas of the array ) on the first call of the the suffle( ) method.



(Edited by poi on 03-07-2005 15:21)