From: Logan Capaldo <logancapaldo@...>
Date: 2006-10-11T23:17:30+09:00
Subject: Re: PHP-like Array/Hash creation in Ruby

On Wed, Oct 11, 2006 at 08:40:06PM +0900, Jan Reitz wrote:
> I used PHP for a long time, a little bit C# and recently started to
> learn about Ruby.
> I do like Ruby very much from the first looks
> It has "my_array.sort" like in c#, not that ugly (imo) "sort($myarray)"
> And it has q'n'd qualitys like php for example: definition at first
> assignment, no need for interfaces and so on.
> 
> But! one thing i really miss from PHP just writing :
>   $my_array[4][5] = "moep"; (no initialize before)
> this does not work in ruby, i had to
>   my_array = Array.new(16) { Array.new 16 }
> first.
> and if the array wasn't great enough i end up with element 16 (the
> 17th) complaining:
>   NoMethodError: undefined method `[]=' for nil:NilClass
> (this only occurs at "my_array[16][5] = 1",
> not at "my_array[4][16] = 1")
> 
Yes, because since you can define [] for anything, ruby has no way of
"guessing" what kind of container you want like PHP does.
> hm, so i thought, if NilClass has no []= method, why dont i define it,
> (i read very often that this is rubys great adv. over most languages
> out there, that u can extend even the basic classes), so it becomes an
> array in that place... but that included "self = Array.new" which
> caused another complaint: "Can't change the value of self"
defining []= for nil is probably not a good idea. What I would suggest
you do is create your own container that has the semantics you want, if
you want to go down the route of writing additional code.
> 
> I read alot of topics about cant change value of self, and i think that
> i have a different problem than these discussed before.
> i dont want to 1.next! => 2 so please dont tell me that i can't do
> that, i know that, and i know its junk
> i want just:
>  hans = nil (or even omit this line)
>  hans[1] = "test"
Like I said previously, since anything can have a [] method, ruby can't
determine that you wanted an array.
> or
>  my_array = Array.new(16) { Array.new 16 }
>  my_array[16][1] = 1
> not:
>  nil[1] = "test"
> 
> I hope my English was well enough to be understood.
Try this:

a = Hash.new { |hash, key| hash[key] = [] }
a[16][1] = "Whee"

or like I said, create your own container. (Creating your own may also
give you a better understanding of why the choices made in ruby are what
they are).