From: Alex LeDonne <aledonne.listmail@...>
Date: 2007-08-21T07:22:19+09:00
Subject: Re: How +:symbol is parsed

On 8/20/07, Victor Zverok Shepelev <vshepelev@imho.com.ua> wrote:
> Hi.
>
> I wanted to be evil and add my own custom semantics to +:some_symbol
> constructs. But I've found such consctructs doesn't call Symbol#+@, while
> +(:some_symbol) does call.
>
> I can suppose it's reason of numbers construction in parser
>
> +3 #doesn't calls Fixnum#+@, it's like Finxum.new(+3),
> +(3) #does calls Fixnum#+@, it's like Fixnum.new(3).+@
>
> but it's still strange for me this rule works for symbols too (but not for
> strings, +"test" calls String#+@). Can somebody please explain this
> strangeness?
>
> Thanks.
>
> V.
>

Well, I haven't looked at parse.y, but I'll wager that the difference
between 3 and "test" is that, for numeric literals, a preceding + or -
is considered the sign of the literal number. That is, +3 is a number
all by itself, whereas +"test" doesn't make sense unless the + is a
method call. There's also no method call when a number is in
exponential notation like -4.3e+11 .

In ruby-ancient times, a symbol was more like an integer, which may or
may not explain the +:symbol semantics.

-A