From: Robert Klemme <bob.news@...>
Date: 2004-01-15T00:51:44+09:00
Subject: Re: Concatenating variable number of Arrays ?


"Johan Holmberg" <holmberg@iar.se> schrieb im Newsbeitrag
news:Pine.GSO.4.50.0401141612480.29527-100000@pjakkur.iar.se...
>
> Hi!
>
> I have been searching for a method to concatenate several arrays.
> A had an Array like this
>
>      arr1 = [ [1,2,3], [4,5,6], [7,[8,9]] ]
>
> and wanted to produce
>
>      arr2 = [1, 2, 3, 4, 5, 6, 7, [8, 9]]
>
> Looking at the methods of the Array class I found some methods that
> do similar things, but none that fits exactly:
>
>     +          concatenate TWO Arrays
>
>     concat     concatenate TWO arrays destructively modifying
>                the first
>
>     flatten    RECURSIVELY flattens elements into a new Array
>
>
> The best way I have found until now, of doing what I want is
>
>     arr2 = arr1.inject([]) {|acc,x| acc.concat x}

That's exactly what I'd do.

> But I feel that the thing I want to do (concatenating a variable
> number arrays) is such a natural thing, that it deserves a cleaner
> way of being expressed.

All other ways that I can think of are more verbose and not necessarily
cleander - let alone faster.  The version using each would look like

arr2=[]
arr1.each {|x| arr2.concat x}

Not really an improvement IMHO.

> Have I  missed some other method that does this in a readable way ?

I don't think so.

    robert