From: "alexeymuranov (Alexey Muranov)" <redmine@...>
Date: 2012-08-15T06:02:29+09:00
Subject: [ruby-core:47193] [ruby-trunk - Feature #6868] Make `do` in block syntax optional when the block is the last argument of a method and is not an optional argument


Issue #6868 has been updated by alexeymuranov (Alexey Muranov).


drbrain (Eric Hodel) wrote:
> =begin
> What would this code do:
> 
>   def method n
>     n = n.times
>     p n
>     n
>   end
> 
> Currently it prints (({#<Enumerator: 3:times>})) and returns an Enumerator.  Would it instead raise SyntaxError for an unexpected end?
> 
> =end

You mean, what should `method(3)` output?  This was not considered in my proposal, i think it should be the same.  In fact, i understand that there are issues with making `def` a method, i was only proposing to make blocks look more like class and method definitions in certain circumstances.  I do not remember if there are Ruby core methods that require a block, all that come to my mind have an optional block parameter.  So here is a made-up example of the use of the proposed syntax:

 def do_three_times(&block)
   3.times(&block)
 end

 do_three_times
   puts "Hi"
 end

The interpreter would need to look up the method definition for `do_three_times` before parsing the parameters (i think this is different from the current behavior), see that there is a required block parameter at the end, and so to expect either `do` or just new line to start the block after `do_three_times`.

----------------------------------------
Feature #6868: Make `do` in block syntax optional when the block is the last argument of a method and is not an optional argument
https://bugs.ruby-lang.org/issues/6868#change-28872

Author: alexeymuranov (Alexey Muranov)
Status: Feedback
Priority: Normal
Assignee: 
Category: core
Target version: 3.0


=begin
I propose to make the use of "(({do}))" in block syntax optional if the block is the last argument of a method and if it is a required argument, at least if the block does not take parameters.  (I think this would be in line with how for example the last hash argument is treated.)  I also think that this syntactic change may allow in future versions of Ruby to make (({def})), (({class})), (({module})) methods instead of keywords.

Something like:

 3.time
   puts "Hi!"
 end

instead of

 3.time do
   puts "Hi!"
 end

I know this is not a good example, because for (({#times})) the block argument is optional.
=end



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