[#43120] [ruby-trunk - Bug #6124][Open] What is the purpose of "fake" gems in Ruby — Vit Ondruch <v.ondruch@...>

27 messages 2012/03/07

[#43142] Questions about thread performance (with benchmark included) — Rodrigo Rosenfeld Rosas <rr.rosas@...>

A while ago I've written an article entitled "How Nokogiri and JRuby

10 messages 2012/03/08

[#43148] [ruby-trunk - Feature #6126][Open] Introduce yes/no constants aliases for true/false — Egor Homakov <homakov@...>

16 messages 2012/03/09

[#43238] [ruby-trunk - Feature #6130][Open] inspect using to_s is pain — Thomas Sawyer <transfire@...>

21 messages 2012/03/11

[#43313] [ruby-trunk - Feature #6150][Open] add Enumerable#grep_v — Suraj Kurapati <sunaku@...>

17 messages 2012/03/15

[#43325] [ruby-trunk - Bug #6154][Open] Eliminate extending WaitReadable/Writable at runtime — Charles Nutter <headius@...>

25 messages 2012/03/16

[#43334] [ruby-trunk - Bug #6155][Open] Enumerable::Lazy#flat_map raises an exception when an element does not respond to #each — Dan Kubb <dan.kubb@...>

9 messages 2012/03/16

[#43370] [ruby-trunk - Feature #6166][Open] Enumerator::Lazy#pinch — Thomas Sawyer <transfire@...>

15 messages 2012/03/17

[#43373] [ruby-trunk - Bug #6168][Open] Segfault in OpenSSL bindings — Nguma Abojo <git.email.address@...>

14 messages 2012/03/17

[#43454] [ruby-trunk - Bug #6174][Open] Fix collision of ConditionVariable#wait timeout and #signal (+ other cosmetic changes) — "funny_falcon (Yura Sokolov)" <funny.falcon@...>

10 messages 2012/03/18

[#43497] [ruby-trunk - Bug #6179][Open] File::pos broken in Windows 1.9.3p125 — "jmthomas (Jason Thomas)" <jmthomas@...>

24 messages 2012/03/20

[#43502] [ruby-trunk - Feature #6180][Open] to_b for converting objects to a boolean value — "AaronLasseigne (Aaron Lasseigne)" <aaron.lasseigne@...>

17 messages 2012/03/20

[#43529] [ruby-trunk - Bug #6183][Open] Enumerator::Lazy performance issue — "gregolsen (Innokenty Mikhailov)" <anotheroneman@...>

36 messages 2012/03/21

[#43543] [ruby-trunk - Bug #6184][Open] [BUG] Segmentation fault ruby 1.9.3p165 (2012-03-18 revision 35078) [x86_64-darwin11.3.0] — "Gebor (Pierre-Henry Frohring)" <frohring.pierrehenry@...>

8 messages 2012/03/21

[#43672] [ruby-trunk - Feature #6201][Open] do_something then return :special_case (include "then" operator) — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>

12 messages 2012/03/26

[#43678] [ruby-trunk - Bug #6203][Open] Array#values_at does not handle ranges with end index past the end of the array — "ferrous26 (Mark Rada)" <markrada26@...>

15 messages 2012/03/26

[#43794] [ruby-trunk - Feature #6216][Open] SystemStackError backtraces should not be reduced to one line — "postmodern (Hal Brodigan)" <postmodern.mod3@...>

15 messages 2012/03/28

[#43814] [ruby-trunk - Feature #6219][Open] Return value of Hash#store — "MartinBosslet (Martin Bosslet)" <Martin.Bosslet@...>

20 messages 2012/03/28

[#43858] [ruby-trunk - Feature #6222][Open] Use ++ to connect statements — "gcao (Guoliang Cao)" <gcao99@...>

12 messages 2012/03/29

[#43904] [ruby-trunk - Feature #6225][Open] Hash#+ — "trans (Thomas Sawyer)" <transfire@...>

36 messages 2012/03/29

[#43951] [ruby-trunk - Bug #6228][Open] [mingw] Errno::EBADF in ruby/test_io.rb on ruby_1_9_3 — "jonforums (Jon Forums)" <redmine@...>

28 messages 2012/03/30

[#43996] [ruby-trunk - Bug #6236][Open] WEBrick::HTTPServer swallows Exception — "regularfry (Alex Young)" <alex@...>

13 messages 2012/03/31

[ruby-core:44018] [ruby-trunk - Feature #6166] Enumerator::Lazy#pinch

From: "trans (Thomas Sawyer)" <transfire@...>
Date: 2012-03-31 17:48:32 UTC
List: ruby-core #44018
Issue #6166 has been updated by trans (Thomas Sawyer).


Also are you sure #first should be non-lazy? e.g.

  max_records = 1000000

  recs = records.first(max_records)

  recs.pinch(@page_no, 25).each do |page_recs|
    ...
  end

Hmm... maybe #page is better name then #pinch?

In any case, the point is I think every enumeration method than can be lazy should be lazy, and a special method that's not an enumerable method should allows us to extract subsets. That method (whether called pinch or something else) would be the most flexible and optimized since it is designed to very task of de-lazying and extraction.


----------------------------------------
Feature #6166: Enumerator::Lazy#pinch
https://bugs.ruby-lang.org/issues/6166#change-25546

Author: trans (Thomas Sawyer)
Status: Rejected
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 


In previous issue #6158 it has been determined that Enumerator::Lazy#take should be lazy. But an eager form of #take would still be useful.

To this end I'll suggest `Enumerator::Lazy#pinch`. Examples of usage:

    e.lazy.pinch 1

    e.lazy.pinch 1..2

    e.lazy.pinch 1,2

It is basically equivalent to calling `to_a[index]`, but has the advantage of being a single invocation instead of two, and reads better.

The #pinch method would be strictly a Lazy method and have no counterpart in Enumerable.



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