From: dblack@...
Date: 2007-07-04T20:10:22+09:00
Subject: Re: Isn't hash default value behavior just a little bizarre?

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Hi --

On Wed, 4 Jul 2007, Farhad Farzaneh wrote:

> Pe=C3=B1a, Botp wrote:
>
>>
>> ruby allows one to change the default value. that is good, imho.
>> i think the surprise stems fr the fact that it is _too simple to change
>> the default. hey, it's ruby ;)
>>
>> kind regards -botp
>
> You're right.  Somehow I missed that in the documentation.... did RTFM,
> but obviously not carefully enough.
>
> Still, I do find it pretty surprising.

All you're doing is assigning an object to a certain role.  There's no
implication of automatic duplication of the object.

> I got stung when I was actually
> using the feature to initialize any entry to an array just to avoid the
> business of
>
> hash[key] ||=3D []

It doesn't do that anyway:

   h =3D {}
   h.default =3D []
   p h["blah"]     # []   (default value for undefined key)
   p h             # {}   (no keys are defined)

The default value is for undefined keys, whereas hash[key] ||=3D []
actually sets a key.


David

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