From: Eric Hodel <drbrain@...7.net>
Date: 2006-03-02T07:11:21+09:00
Subject: Re: Newby question: Is += atomic for integers?

On Mar 1, 2006, at 2:08 PM, rj-cole wrote:

> Hi,
>
> Can the following program produce counts that are wrong?
>
> class Test
>   attr_accessor :count
>   def initialize
>     @count = 0
>   end
> end
>
> $test = Test.new
>
> def my_function_called_by_many_threads
>   ...
>   $test.count += 1
>   ...
> end

Yes.  += is just syntax sugar.  It gets expanded:

$ parse_tree_show -f
a += 1
[[:class,
   :Example,
   :Object,
   [:defn,
    :example,
    [:scope,
     [:block,
      [:args],
      [:lasgn, :a, [:call, [:lvar, :a], :+, [:array, [:lit, 1]]]]]]]]]

> Any why is the following a syntax error?
>
> class Test
>   def +=(value)
>   end
> end
>
> i.e why can't I define the += operator?

+= is not an operator, it is syntax sugar.

-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
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