[ruby-talk:5163] Re: Types and ===

----- Original Message ----- 
From: <[e-mail]>
To: ruby-talk ML <[e-mail]>
Sent: Wednesday, September 27, 2000 2:25 PM
Subject: [ruby-talk:5161] Re: Types and ===


> | Because many of the world's common prepositional and similarity
> | relations (if you are going to include them in the "===" realm) just
> | don't work that way in general (special cases notwithstanding); hence
> | my original question
> ...
> | But here is a still more general question: why would you want to
> | preclude "===" from potentially being *any* suitable 2-place predicate
> | method whatsoever?
> 

OK, I see what you are saying...

> In other words....
> 
> AFAIK, the principal use/purpose of "===" is "case equality" for case
> statements. (IMHO this is an unfortunately somewhat over-specialized name
> for a more general concept--I would have preferred something more generic
> or more generalized such as "case matching".) Since there are so many
> sorts of relations that are not symmetric with respect to swapping their
> arguments that people might quite reasonably want to use in case
> statements, then unless I am missing something else here, I don't see how
> precluding the usage of such methods wouldn't eventually become a very
> onerous restriction.
> 

OK... I think I understand that.

However, I'm still puzzled by two things:
1. Why do we say "case other; when receiver" and not
"case receiver; when other"?
2. Why is the argument order for pattern === string opposite
from the order for string =~ pattern?

It almost (I'm not serious here, not entirely) makes me want to propose
two more operators ==> and <== which point to the receiver... then
the === could be used for symmetrical cases.

Hal