[#42344] [ruby-trunk - Feature #5964][Open] Make Symbols an Alternate Syntax for Strings — Tom Wardrop <tom@...>

23 messages 2012/02/03

[#42443] [ruby-trunk - Bug #5985][Open] miniruby skews "make benchmark" results — Eric Wong <normalperson@...>

21 messages 2012/02/08

[#42444] [ruby-trunk - Bug #5986][Open] Segmentation Fault — Luis Matta <levmatta@...>

16 messages 2012/02/08

[#42471] [ruby-trunk - Feature #5995][Open] calling io_advise_internal() in read_all() — Masaki Matsushita <glass.saga@...>

20 messages 2012/02/10

[#42560] [ruby-trunk - Bug #6011][Open] ruby-1.9.3-p0/lib/webrick/utils.rb:184: [BUG] Segmentation fault — Vit Ondruch <v.ondruch@...>

12 messages 2012/02/13

[#42579] [ruby-trunk - Bug #6012][Open] Proc#source_location also return the column — Roger Pack <rogerpack2005@...>

14 messages 2012/02/14

[#42685] [ruby-trunk - Bug #6036][Open] Test failures in Fedora Rawhide/17 — Bohuslav Kabrda <bkabrda@...>

14 messages 2012/02/16

[#42697] [ruby-trunk - Bug #6040][Open] Transcoding test failure: Big5 to UTF8 not defined (MinGW) — Luis Lavena <luislavena@...>

10 messages 2012/02/16

[#42813] [ruby-trunk - Feature #6065][Open] Allow Bignum marshalling/unmarshalling from C API — Martin Bosslet <Martin.Bosslet@...>

22 messages 2012/02/23

[#42815] [ruby-trunk - Bug #6066][Open] Fix "control may reach end of non-void function" warnings for clang — Eric Hodel <[email protected]>

15 messages 2012/02/23

[#42857] [ruby-trunk - Feature #6074][Open] Allow alias arguments to have a comma — Thomas Sawyer <transfire@...>

20 messages 2012/02/24

[#42891] [ruby-trunk - Feature #6083][Open] Hide a Bignum definition — Koichi Sasada <redmine@...>

23 messages 2012/02/25

[#42906] [ruby-trunk - Bug #6085][Open] Treatment of Wrong Number of Arguments — Marc-Andre Lafortune <ruby-core@...>

14 messages 2012/02/25

[#42949] [ruby-trunk - Bug #6089][Open] Test suite fails with OpenSSL 1.0.1 — Vit Ondruch <v.ondruch@...>

13 messages 2012/02/26

[ruby-core:42854] [ruby-trunk - Feature #6073] Proposal of extending syntax of for loop

From: Shugo Maeda <redmine@...>
Date: 2012-02-24 05:48:56 UTC
List: ruby-core #42854
Issue #6073 has been updated by Shugo Maeda.


Hi,

Shouichi KAMIYA wrote:
> 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

I'm interested in your idea.
# Feature #6070 was preparation for the same proposal.

> 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

Scala's for expression is more powerful.
If yield in used in a for expression, nested loop is converted to a combination of map/flatMap/withFilter.

For example, the following code:

  for z in (1..Float::INFINITY).lazy
      x in 1..z
      y in x..z
      when x**2 + y**2 == z**2
    yield [x, y, z]
  end

is equivalent to the following code:

  (1..Float::INFINITY).lazy.flat_map {|z|
    (1..z).flat_map {|x|
      (x..z).select {|y|
        x**2 + y**2 == z**2
      }.map {|y|
        [x, y, z]
      }
    }
  }

Please note that yield is already take in Ruby, so we need different Syntax.

What do you think of that feature?

----------------------------------------
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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