From: "marcandre (Marc-Andre Lafortune)" <ruby-core@...>
Date: 2012-03-20T02:27:39+09:00
Subject: [ruby-core:43478] [ruby-trunk - Bug #6155] Enumerable::Lazy#flat_map raises an exception when an element does not respond to #each


Issue #6155 has been updated by marcandre (Marc-Andre Lafortune).


Hi,

shugo (Shugo Maeda) wrote:
> Why the last example defines to_a?  flat_map doesn't call to_a, but to_ary.

I think it's to spec that it doesn't call `to_a`.

----------------------------------------
Bug #6155: Enumerable::Lazy#flat_map raises an exception when an element does not respond to #each
https://bugs.ruby-lang.org/issues/6155#change-24948

Author: dkubb (Dan Kubb)
Status: Closed
Priority: Normal
Assignee: shugo (Shugo Maeda)
Category: core
Target version: 2.0.0
ruby -v: ruby 2.0.0dev (2012-03-15 trunk 35028) [x86_64-darwin11.3.0]


The following statement will raise "NoMethodError: undefined method `each' for 1:Fixnum":

  [1, 2, 3].lazy.flat_map { |n| n }.to_a

It appears as if Enumerable::Lazy#flat_map is calling #each on every element, regardless of whether it can work or not.

As a reference, the equivalent statement using Enumerable#flat_map works:

  [1, 2, 3].flat_map { |n| n }.to_a


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