From: "matz (Yukihiro Matsumoto)" <matz@...>
Date: 2012-04-02T10:42:20+09:00
Subject: [ruby-core:44052] [ruby-trunk - Feature #6166] Enumerator::Lazy#pinch


Issue #6166 has been updated by matz (Yukihiro Matsumoto).


I am not sure what you mean by "does not act in place".  Lazy sequence has position.  Retrieving value from sequence moves its position, even calling to_a. So to make #pinch work as if "not acting in place", sequence needs to keep the values inside, everytime it generates.

I don't want to do that since it hinders the best benefit from "lazy" sequence.

Matz.
 
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Feature #6166: Enumerator::Lazy#pinch
https://bugs.ruby-lang.org/issues/6166#change-25582

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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