From: Caleb Clausen <vikkous@...>
Date: 2010-07-06T22:07:05+09:00
Subject: Re: WTF? Case statement disfunctional?

On 7/6/10, Pieter Hugo <pieter@internext.co.za> wrote:
> Hi guys
>
> Thanks for the prompt and helpful responses. Your proposals work, but I
> am still unhappy about spending an hour tracking this bug.
>
> So CASE uses '===' and not '==', am I correct? So why does
>
> a = 1
> a === Fixnum
>
> ==> false

but,
  Fixnum===a      #=>true

=== is not symmetric with respect to its arguments. I forget what the
right word for that is.


> Furthermore, In my original example, one would expect a.class === Fixnum
> to return true in any case, as '===' is supposed to be more forgiving
> than '==', but it doesn't.

Don't think of === as a 'more forgiving' ==. It doesn't provide a
superset of =='s behavior; it's more like a better equality operator
for use in case expressions. === actually has rather complicated
semantics which depend on the type of its left-side argument, so it's
hard to come up with a pithy one-line description.