[#47790] [ruby-trunk - Bug #7097][Open] Thread locals don't work inside Enumerator — "tenderlovemaking (Aaron Patterson)" <aaron@...>

32 messages 2012/10/01
[#47791] [ruby-trunk - Bug #7097][Assigned] Thread locals don't work inside Enumerator — "kosaki (Motohiro KOSAKI)" <kosaki.motohiro@...> 2012/10/01

[#47792] Re: [ruby-trunk - Bug #7097][Assigned] Thread locals don't work inside Enumerator — Aaron Patterson <tenderlove@...> 2012/10/01

On Tue, Oct 02, 2012 at 03:05:17AM +0900, kosaki (Motohiro KOSAKI) wrote:

[#47798] Re: [ruby-trunk - Bug #7097][Assigned] Thread locals don't work inside Enumerator — SASADA Koichi <ko1@...> 2012/10/01

(2012/10/02 3:12), Aaron Patterson wrote:

[#47800] Re: [ruby-trunk - Bug #7097][Assigned] Thread locals don't work inside Enumerator — SASADA Koichi <ko1@...> 2012/10/01

(2012/10/02 8:22), SASADA Koichi wrote:

[#47832] [ruby-trunk - Feature #7106][Open] FileUtils.touch should allow touching the symlink itself rather than the file the link points to — "cirrusthinking (Alessandro Diaferia)" <alessandro@...>

18 messages 2012/10/04

[#47847] [ruby-trunk - Bug #7110][Open] CGI: Add support for HTML5 <header> tag — "stomar (Marcus Stollsteimer)" <redmine@...>

16 messages 2012/10/05

[#47870] [ruby-trunk - Bug #7123][Open] Segmentation fault in ruby 1.9.3-p194 — "mscottford (M. Scott Ford)" <scott@...>

13 messages 2012/10/09

[#47880] [ruby-trunk - Bug #7134][Open] Signal handling bug in Mac OS X — "auastro (Andy Kitchen)" <kitchen.andy+rubybug@...>

17 messages 2012/10/10

[#47881] [ruby-trunk - Bug #7135][Open] GC bug in Ruby 1.9.3-p194? — "alexdowad (Alex Dowad)" <alexinbeijing@...>

21 messages 2012/10/10

[#47887] [ruby-trunk - Bug #7137][Open] Date.parse overly lenient when attempting to parse Monday? — "garysweaver (Gary Weaver)" <garysweaver@...>

12 messages 2012/10/10

[#47930] [ruby-trunk - Feature #7148][Open] Improved Tempfile w/o DelegateClass — "Glass_saga (Masaki Matsushita)" <glass.saga@...>

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[#47970] [ruby-trunk - Bug #7158][Open] require is slow in its bookkeeping; can make Rails startup 2.2x faster — "gregprice (Greg Price)" <price@...>

30 messages 2012/10/14

[#48027] [Backport93 - Backport #7172][Open] [[Ruby 1.9:]] fix rbconfig for --enable-load-relative (v2) — "mpapis (Michal Papis)" <mpapis@...>

13 messages 2012/10/16

[#48053] [ruby-trunk - Bug #7180][Open] set_trace_func with error in proc block locks up Ruby with 100% cpu usage and no way to exit without killing proc — "garysweaver (Gary Weaver)" <garysweaver@...>

8 messages 2012/10/17

[#48072] [ruby-trunk - Bug #7184][Open] --disable-gems commandline parameter does not show up with ruby -h — "steenslag (siep korteling)" <s.korteling@...>

10 messages 2012/10/18

[#48130] [ruby-trunk - Bug #7200][Open] Setting external encoding with BOM| — "brixen (Brian Ford)" <brixen@...>

14 messages 2012/10/21

[#48191] [ANN] 2.0.0 feature freeze — Yusuke Endoh <mame@...>

Japanese later; 日本語は後で

37 messages 2012/10/24
[#48696] Re: [ANN] 2.0.0 feature freeze — SASADA Koichi <ko1@...> 2012/11/01

(2012/10/24 5:39), Yusuke Endoh wrote:

[#48260] [ruby-trunk - Bug #7214][Open] Ruby 2.0 breaks support for some debugging tools — "banister (john mair)" <jrmair@...>

22 messages 2012/10/25

[#48315] [ruby-trunk - Bug #7220][Open] StringIO#initialize_copy causes aliasing between the objects — "brixen (Brian Ford)" <brixen@...>

13 messages 2012/10/26

[#48413] [ruby-trunk - Bug #7221][Open] Unable to compile kgio under 1.9.3 with error: ruby-1.9.3-<plvl>/lib/ruby/1.9.1/mkmf.rb:597:in `Integer': can't convert nil into Integer (TypeError) — "davidderyldowney (David Deryl Downey)" <me@...>

9 messages 2012/10/27

[#48549] [ruby-trunk - Feature #7240][Open] Inheritable #included/#extended Hooks For Modules — "apotonick (Nick Sutterer)" <apotonick@...>

14 messages 2012/10/29

[#48551] [ruby-trunk - Feature #7241][Open] Enumerable#to_h proposal — "nathan.f77 (Nathan Broadbent)" <nathan.f77@...>

23 messages 2012/10/29

[#48552] [ruby-trunk - Bug #7242][Open] Bignum mathematical accuracy regression in r31695 — "mhall (Matthew Hall)" <mhall@...>

11 messages 2012/10/29

[ruby-core:48551] [ruby-trunk - Feature #7241][Open] Enumerable#to_h proposal

From: "nathan.f77 (Nathan Broadbent)" <nathan.f77@...>
Date: 2012-10-29 22:23:29 UTC
List: ruby-core #48551
Issue #7241 has been reported by nathan.f77 (Nathan Broadbent).

----------------------------------------
Feature #7241: Enumerable#to_h proposal
https://bugs.ruby-lang.org/issues/7241

Author: nathan.f77 (Nathan Broadbent)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 


I often use the `inject` method to build a hash, but I always find it annoying when I need to return the hash at the end of the block.
This means that I often write code like:

    [1,2,3,4,5].inject({}) {|hash, el| hash[el] = el * 2; hash }

I'm proposing an `Enumerable#to_h` method that would let me write:

    [1,2,3,4,5].to_h {|h, el| h[el] = el * 2 }


I saw the proposal at http://bugs.ruby-lang.org/issues/666, but I would not be in favor of his implementation.
I believe the implementation should be similar to `inject`, so that the hash object and next element are passed to the block. The main difference to the `inject` method is that we would be modifying the hash in place, instead of relying on the block's return value.

As well as providing support for the case above, I have also considered other cases where the `to_h` method would be useful.
I thought it would be useful if symmetry were provided for the `Hash#to_a` method, such that:

    hash.to_a.to_h == hash  # => true

(See example 2)


I've allowed developers to provide a symbol instead of a block, so that each element in the collection will be passed to that named method. (See example 3)

Finally, hashes can be given a default value, or a Proc that returns the default value. (See examples 4 & 5)


Heres an example implementation that I would be happy to rewrite in C if necessary:


    module Enumerable
      def to_h(default_or_sym = nil)
        if block_given?
          hash = if Proc === default_or_sym
            Hash.new(&default_or_sym)
          else
            Hash.new(default_or_sym)
          end
          self.each do |el|
            yield hash, el
          end
        elsif !default_or_sym.nil?
          hash = {}
          self.each do |el|
            hash[el] = el.send(default_or_sym)
          end
        else
          return Hash[*self.to_a.flatten(1)]
        end
        hash
      end
    end


Examples
----------------------------------------------


# 1) Build a hash from array elements

    [1,2,3,4,5].to_h {|h, el| h[el] = el * 2 }

=> {1=>2, 2=>4, 3=>6, 4=>8, 5=>10}


# 2) Provides symmetry for Hash.to_a (i.e. you can call hash.to_a.to_h)

    [[1, 2], [3, 4], [5, 6]].to_h

=> {1=>2, 3=>4, 5=>6}


# 3) Build a hash by calling a method on each array element

    ["String", "Another String"].to_h(:size)

=> {"String"=>6, "Another String"=>14}


# 4) Hash with default value

    [4,5,6,5].to_h(0) {|h, el| h[el] += el }

=> {4=>4, 5=>10, 6=>6}


# 5) Hash with default value returned from Proc

    default_proc = -> hash, key { hash[key] = "go fish: #{key}" }
    [4,5,6].to_h(default_proc) {|h, el| h[el].upcase! }

=> {4=>"GO FISH: 4", 5=>"GO FISH: 5", 6=>"GO FISH: 6"}



Thanks for your time, and please let me know your thoughts!


Best,
Nathan Broadbent


-- 
http://bugs.ruby-lang.org/

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