From: "David A. Black" <dblack@...>
Date: 2010-04-14T08:44:21+09:00
Subject: Re: I thought spaces didn't matter around operators

Hi --

On Wed, 14 Apr 2010, Rob Biedenharn wrote:

>
> On Apr 13, 2010, at 7:24 PM, Sarah Allen wrote:
>
>> I had understood that operators, like minus (-), had special "syntactic
>> sugar" that allowed me to include or omit spaces around them like this:
>> 
>>>> 1-1
>> => 0
>>>> 1 -1
>> => 0
>>>> 1 - 1
>> => 0
>>>> 1- 1
>> => 0
>> 
>> However, in some cases, spaces seem to matter:
>> 
> irb> t=Time.now
> => Tue Apr 13 19:27:43 -0400 2010
> irb> Time.now() -t
> => 5.824652
> irb> Time.now -t
> NoMethodError: undefined method `-@' for Tue Apr 13 19:27:43 -0400 2010:Time
> 	from (irb):5
> 	from :0
> irb> -t
> NoMethodError: undefined method `-@' for Tue Apr 13 19:27:43 -0400 2010:Time
> 	from (irb):6
> 	from :0
>
> The flexible syntax also lets you omit parentheses and in this case, the "-t" 
> is parsed as an argument to the Time.now method.  Putting the explicit (and 
> empty) argument list on the call removes this ambiguity.

Here's another interesting space/non-space case:

   >> def m(*args); "hi"; end
   => nil
   >> m *10
   => "hi"
   >> m * 10
   => "hihihihihihihihihihi"

In m *10 the * is the unary *, while in m * 10 it's the infix
operator/method *.


David

-- 
David A. Black
Senior Developer, Cyrus Innovation Inc.
THE COMPLEAT RUBYIST, Ruby training with Black/Brown/McAnally!
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