From: Shouichi KAMIYA <shouichi.kamiya@...>
Date: 2012-02-27T11:44:11+09:00
Subject: [ruby-core:42966] [ruby-trunk - Feature #6073] Proposal of extending syntax of for loop


Issue #6073 has been updated by Shouichi KAMIYA.


Hi,

Shugo Maeda wrote:
> I think it's good to support both each and map/flat_map.
> It may be possible to use yield instead of do/;/newline when using map/flat_map.
> 
>   # use each
>   for i in obj
>     ...
>   end
> 
>   # use map; yield is not a block call
>   for i in obj yield
>   end
> 
>   # use each; yield is a block call
>   for i in obj
>     yield i
>   end
>   for i in obj do yield i end
>   for i in obj; yield i end
> 
> It might be too confusing, though.

Though supporting both each and map/flat_map makes code simpler but,
I'm not completely sure if it's a good idea. I think we've got to
get more people involved and discuss.

About the syntax, I don't come up with better syntax right now.
----------------------------------------
Feature #6073: Proposal of extending syntax of for loop
https://bugs.ruby-lang.org/issues/6073

Author: Shouichi KAMIYA
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


Hi,

I propose to extend syntax of for loop which allows us to write multiple loop with guard easily.
This extension is inspired by Scala. Here is a example

for i in 1..4 when i % 2 == 0
    j in 5..8 when j % 4 == 0
  puts "#{i}, #{j}"
end

Above code is same as following code.

for i in 1..4
  if i % 2 == 0
    for j in 5..8
      if j % 4 == 0
        puts "#{i}, #{j}"
      end
    end
  end
end

I already implemented this syntax and attached a patch.
What do you think about this syntax guys?

Thank you,
Shouichi


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