From: "trans (Thomas Sawyer)" <transfire@...>
Date: 2012-04-01T03:47:23+09:00
Subject: [ruby-core:44026] [ruby-trunk - Feature #6166] Enumerator::Lazy#pinch


Issue #6166 has been updated by trans (Thomas Sawyer).


I don't care about name "#pinch", but functionality. Using #first with #drop is not always optimal.

1) Given d = [index,length].

  enum.drop(d.first).first(d.last)

2) Given a range (e.g. `rng = 2...4`):

  if rng.exclude_end?
    enum.drop(rng.begin).first(rng.end-1)
  else
    enum.drop(rng.begin).first(rng.end)
  end

`enum(*d)` and `enum(rng)` is much better.

Also I take it #drop is lazy?

----------------------------------------
Feature #6166: Enumerator::Lazy#pinch
https://bugs.ruby-lang.org/issues/6166#change-25553

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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