From: Caleb Clausen <vikkous@...>
Date: 2009-12-22T12:45:10+09:00
Subject: Re: Strange behavior of unary +@ for Fixnum?

On 12/21/09, Colin Bartlett <colinb2r@googlemail.com> wrote:
> I haven't looked at the source code, but I think I'm right in saying that
> Ruby parses (-7) as an _integer literal_, unless it's an expression like
> (-7**2)
> in which case it's parsed as (-(7**2)), that is (7**2).send( :-@ )
> By analogy, it seems that the parser is treating (+7) as an integer literal,
> not as 7.send( :+@ ) ?

This is correct. + or - at the start of an numeric literal is
tokenized as part of that literal. (Except in the ** case, as you
say.)

The situation is somewhat better in 1.9, where at least
 + 7 #with a space in between
is treated as +@ method applied to the literal 7. But that doesn't
help in 1.8. Note that in ruby 1.8, any number of leading + signs are
glommed into the integer literal:

  ++++++++++++++++++++++++++7  #still no method call in 1.8

Having integer literals eat up the leading + or - as part of the
number token is a common 'optimization' in many languages...