From: dblack@...
Date: 2006-07-29T06:47:50+09:00
Subject: Re: does ":" have an anolog in another language?

Hi --

On Sat, 29 Jul 2006, nothinghappens@mchsi.com wrote:

>
> -------------- Original message ----------------------
> From: dblack@wobblini.net
>> Ruby symbols aren't exactly used as variable names, though.  If you
>> assign to a variable:
>>
>>     a = 1
>>
>> then Ruby creates and stores an :a symbol.  But if you use the symbol
>> :a, like this:
>>
>>    b = :a
>>
>> there's no direct semantic connection to your variable called 'a'.
>
> Well, that just makes it even *more* like Lisp than I was thinking.  It hadn't occurred to me
> that Ruby creates a symbol for a variable.  But I guess it makes
> sense given some code I've seen that uses symbols to name methods
> and attributes and the like.  assigning b = :a is like doing (setf b
> 'a) in Lisp, b contains a symbol, not 1 or a reference to the
> variable a itself or anything like that.  What I wonder then, is
> what happens in Ruby if you were to then call eval(b) ?  I haven't
> tried it.

eval wants a string:

   eval(b)
   TypeError: can't convert Symbol into String

I think a case could be made for a Symbol#to_str method, since there
can't be anything that eval(sym) would mean except to eval a string
representation of the symbol, and same for appending symbols to
strings.  But I don't know whether there are hidden complications I'm
not thinking of.


David

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