From: dblack@...
Date: 2007-09-03T20:12:54+09:00
Subject: Re: Ruby stupidities

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Hi --

On Mon, 3 Sep 2007, Matthias W=C3=A4chter wrote:

> On 31.08.2007 05:24, Kenneth McDonald wrote:
>> Having said that, here's my first entry. I think it's utterly stupid
>> (can you tell I just wasted some time tracking this down?) that
>>
>>    "abc"[0] =3D=3D "a"
>
> You can change that behavior yourself without installing >=3D1.9
>
> class String
>  alias :old_index :[]
>  def [](*a)
>    a.length=3D=3D1 ? old_index(*a).chr : old_index(*a)
>  end
>  def asc       # this is from [1]
>    case size
>      when 0; nil
>      when 1; old_index(0)
>      else unpack 'c*'
>    end
>  end
> end
>
> "abc"[0] =3D=3D "a"       # -> true
> "abc"[1] =3D=3D "b"       # -> true
> "abc"[0,1] =3D=3D "a"     # -> true
> "a".asc =3D=3D 97         # -> true
> "abc".asc =3D=3D [97,98,99] # -> true
>
> But certainly this may break existing libs, so be careful.

The problem is, you can't be careful. You can only decide that it's OK
for code to break, and keep your fingers crossed that it doesn't.

I don't mean to split hairs -- of course "careful" can mean lots of
things. It's just that I think it's important to remember that the
code doesn't "know" that the person who changed it is worried :-) It's
just going to do what it does. So unless you're willing to read
through the entire source code base, for Ruby and all add-on
libraries, every time you make such a change, you're pretty much
accepting some very real risk.


David

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