From: Joel VanderWerf <vjoel@...>
Date: 2007-11-16T07:11:10+09:00
Subject: Re: (1..5) === 3 > true 3 === (1..5) > false

Michael Chow wrote:
> (1..5) === 3 > true
> 3 === (1..5) > false
> 
> Is this a bug or expected behavior? From my understanding it shouldn't
> matter on which side of an equal comparison an expression appears.

It's normal for the #=== operator to be asymmetric, even though it looks 
symmetric. The LHS is treated as a _pattern_ for matching the RHS.

For example:

String === "foo"

uses different criteria than

"foo" === String

and likewise for

/fo/ === "foo"

vs

"foo" === /fo/

Also, note that #=== is used in case statements.

case 3
when 1..5
   ...
end

works as you expect, because it is equivalent to

if (1..5) === 3
   ...
end

But this wouldn't make sense:

case 1..5
when 3
   ...
end

so it really needs to be asymmetric.

-- 
        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407