Feature #729: curly brackets" and "begin end" blocks should behave syntactically and semantically exactly the same

• Status: Rejected
• Assignee: -
• Target version: -

[tpo (Tomas Pospisek)]

(transported over from rubyforge #16111, as I still think this would be worth while...)

Every now and then I run into a "principle of least surprise" violation wrt blocks in Ruby.

The most primitive problem i have is this: why does the following work:

# the code below is grouped together because it represents
# a semantic whole:
begin
  do_something
  and_then_something_else
end

but this here bails out with a syntax error:

# the following code is grouped together because it represents
# a semantic whole:
{
  do_something
  and_then_something_else
}

In every other language I know that has curly braces as block delimiters, the above is alowed and natural. Except Ruby.

The above code is a special case. I am not sure it can be fixed without breaking Ruby syntax as a whole. I think it can.

To me "curly brackets" and "begin end" should act semantically and syntactically exactly the same.
I.e. all the following forms should IMHO be allowed and identical:

if condition
end

if condition begin
end

if condition {
}

The same would apply to all other ruby control structures.

Unfortunately it seems it is not be possible to fix the general case without breaking Ruby since Ruby expects that "condition" above could also in itself be a block since both:

if { condition }
end

and

if begin condition end
end

are allowed and make sense, but contradict my wish above, since allowing the above proposed change would actually make the syntax more ambiguous and make it harder for the parser to help the programmer with syntax errors.

[antares (Michael Klishin)]

=begin

In every other language I know that has curly braces as block delimiters, the above is alowed and natural. Except Ruby.

Python does not use curly braces for if statements, and AFAIK nether Python community, nor Ruby community really cares about curly braces for if statements. If you ask me, I'd say curly braces are ugly, so calling it natural is a matter of taste. I don't think that Ruby which historically never tried to be C-like language, really needs to become closer to C.
=end

[matz (Yukihiro Matsumoto)]

• Status changed from Open to Rejected

You shouldn't mention principle of least surprise of YOURSELF in the
proposal, for background varies for everyone. You have no rights to
change the language (especially in incompatible way) to adopt your
personal preference before accustoming yourself to the language,
unless you're the creator of the language. Even Ruby surprised you,
it is so for good reasons.

If you use Ruby for a while (e.g. at least a year of so), and you
still feel it should be changed for good reasons, come again.

						matz.

[cout (Paul Brannan)]

On Sun, Nov 09, 2008 at 05:08:29AM +0900, Tomas Pospisek wrote:

To me "curly brackets" and "begin end" should act semantically and
syntactically exactly the same.

Except for precedence, the curly brackets are the same as do..end, not
begin..end.

I think the real question is why do and begin are different. This
confused me when I first started using ruby, but now I am used to it.

Paul

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)