[ruby-core:32722] Re: [Ruby 1.9-Feature#3845][Open] "in" infix operator

Hi,

2010/10/8 "Martin J. D=FCrst" <[e-mail]>:
> I would understand that if it were [a, b, c].included? x
> But it's include?, so the order seems just fine. Easy to read as
> "does [a, b, c] include x?". Any other order would feel strange, wouldn't
> it?

I'm not talking about English, but a "subject" of a sentence.
Because I think that the "subject" of this sentence is "x", I want to
write "x" first, such as "is x included in [a, b, c]?".

Consider Python's join:  '-'.join(["a", "b", "c"])
I think that it is awkward NOT because it is unnatural English word order,
but because an array (that is the "subject" of this sentence) appears
later.


> Also, an 'in?' method on Object has been proposed, so that you can write
> x.in? [a, b, c]
> That's very short, and fully object oriented pure Ruby, no syntactic suga=
r
> necessary.

Some people say that it is against OO.  They say that Object class should
not have "in?" method because "in?" is not a property of Object.
Personally, I'm not against Object#in?, but I can also understand their
opinions.


>> =A0 2) the idiom is too long (even though it is often used)
>
> I don't think Ruby method names are optimized according to usage frequenc=
y.

Though there are many exceptions, Ruby certainly has a design principle
("akr theory" called in [ruby-dev:33558]) that encouraged methods should
have short names.

An extreme example is [ruby-dev:33553].  matz once suggested String#sg
that is a reformed version of String#gsub.  Though it was not committed.


> Another way to do it would be:
> =A0 =A0case http_request.http_method
> =A0 =A0when :get, :post, :put, :delete
> =A0 =A0 =A0...
> =A0 =A0end

I agree that case statement is a good idea.  When I imformally suggested
"in?" operator (on IRC or twitter), some people also suggested me to use
case statement, and I was satisfied once.

But there is still two problems; case cannot be postpositive, and cannot
be used in else clauses (like "elsif").


An extreme example again: I heard that Sasada-san even created a patch for
postpositive case statement:

  p "foo" case http_request.http_method when :get, :post, :put, :delete

I believe that this shows that many people suffer from the word order
problem, though "in" operator is much better than this syntax :-)

--=20
Yusuke Endoh <[e-mail]>