From: Rob Biedenharn <Rob@...>
Date: 2010-04-15T05:20:47+09:00
Subject: Re: I thought spaces didn't matter around operators

On Apr 14, 2010, at 3:47 PM, Sarah Allen wrote:
> Brian Candler wrote:
>> -@ is the unary minus method, +@ is the unary plus method.
>>
>> class Foo
>>  def -@
>>    "Minused"
>>  end
>>  def +@
>>    "Plussed"
>>  end
>> end
>
> This is a very helpful example.
>
> But, I still can't fully answer my original question
>
>>> 1 + 1
> is the same as
>>> 1.send(:+, 1)
>
>>> 1 +1
> is the same as...?
>>> 1 1.send(:+@)
> SyntaxError: compile error
> (irb):8: syntax error, unexpected tINTEGER, expecting $end
> 1 1.send(:+@)
>   ^
>  from (irb):8
>
> nope.
>
> So, in what way is 1 +2 not like 1 +t (where t is a Time object). I  
> know
> 2 is a FixNum, but why is that significant?  Specifically, how is the
> expression evaluated to make 1 +1 work?

 From your original,
   Time.now -t
now is a method call
   1 -t
1 is not a method call

>
>>> t = 2
> => 2
>>> 1 +t
> => 3
>>> t = Time.now
> => Wed Apr 14 12:46:30 -0700 2010
>>> 1 +t
> TypeError: Time can't be coerced into Fixnum
>  from (irb):19:in `+'
>  from (irb):19

There's no coerce method for a Time instance.

Try this:

t = Time.now
1 + t

Then do:

class Time
   def coerce(other)
     case other
     when Integer
       return other, self.to_i
     else
       super
     end
   end
end

And retry:

1 + t

This is a different issue than the parser trying to apply :+@

-Rob

>
>
> Thanks!
> Sarah
> -- 
> Posted via http://www.ruby-forum.com/.
>

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com