From: Robert Klemme <bob.news@...>
Date: 2005-06-09T21:15:32+09:00
Subject: Precedence (was: Order of operations)

Jack Christensen wrote:
> Just got bit by a little order of operations confusion.
>
> irb(main):012:0> a = nil or 1
> => 1
> irb(main):013:0> a
> => nil
> irb(main):014:0> a = (nil or 1)
> => 1
> irb(main):015:0> a
> => 1

But note:

>> a = nil || 1
=> 1
>> a
=> 1
>>
> Probably old news to long time rubyists but it surprised me. Is there
> any way to get a warning or something when a statement like the above
> may not be behaving like you would think?

No, because Ruby cannot know what you expect.  But note that there *are*
warnings:

>> if ( a = 10 )
>> "ja"
>> end
(irb):3: warning: found = in conditional, should be ==
=> "ja"
>>

"or" and "and" have much lower precedence than "||" and "&&" to give you
the choice and for example do things like

arr.empty? and puts "it's empty!"
a > 0 and puts "positive"

Kind regards

    robert