From: Benoit Daloze <eregontp@...>
Date: 2009-11-14T01:22:22+09:00
Subject: Re: RCR enumerable extra into core

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Hi,

I'm quite conservative or maybe 'wise', seeing this discussion.

In fact, using arr.map(:method, arg1 ... ) is too confusing to me
While the &:method notation is clear, and not that ugly.

And I think it has to be a separation between blocks and arguments; block is
another "kind" of argument.
That's why I think we should keep the &:method, and forget about :method.
Note also that is not a common use of &:method, because you often need to do
ore than one thing with the element. eg:
[1,15,3].map { |e| e.to_s.length }

P.S.:
Why &:method is faster ? (Bad, I wanted to argue &:method is slower but I
can't ...)
(requiring and including Benchmark)
irb(main):008:0> realtime { (1..1000000).to_a.map &:to_s  }
=> 0.38111090660095215
irb(main):009:0> realtime { (1..1000000).to_a.map { |e| e.to_s } }
=> 0.445728063583374


2009/11/11 David A. Black <dblack@rubypal.com>

> Hi --
>
>
> On Wed, 11 Nov 2009, Brian Candler wrote:
>
>  Rick Denatale wrote:
>>
>>> On Tue, Nov 10, 2009 at 10:47 AM, Brian Candler <b.candler@pobox.com>
>>> wrote:
>>>
>>>> other Enumerators. When you want a real array, then add .to_a to the
>>>> end.
>>>>
>>>
>>> And you base this ultimate conclusion on what?
>>>
>>
>> The OP was asking whether map(:foo) should return an Array or an
>> Enumerator. I was trying to say that if you're ambivalent about this,
>> one logical conclusion (or extreme viewpoint) is that you could always
>> return an Enumerator, even for
>>
>>  map { |x| x*x }
>>
>> I wasn't saying that Ruby does anything like this, and it's a tangent to
>> the original thrust of map(:foo).
>>
>
> This reminds me of the early 1.9.0 thing, where you could do:
>
>  array = [1,2,3,4]
>  enum = array.enum_for(:map, &lambda {|x| x * x })
>
>  enum.next   # 1
>  enum.next   # 4
>
> etc. (That's ruby 1.9.0 (2008-03-01 revision 15660)
> [i686-darwin9.2.0].) To be honest, when that disappeared, it seemed to
> me to do away with a great deal of the usefulness of enumerators.
> Given that you can no longer attach a block to an enumerator when you
> create the enumerator, I don't think there are any actual use cases
> for the fact that map returns an enumerator (or at least very, very
> few). You can't do this, for example (following the above example):
>
>  enum.select {|x| x > 1 } # [4, 9, 16]
>
>
>
> David
>
> --
> The          Ruby training with D. Black, G. Brown, J.McAnally
> Compleat     Jan 22-23, 2010, Tampa, FL
> Rubyist      http://www.thecompleatrubyist.com
>
> David A. Black/Ruby Power and Light, LLC (http://www.rubypal.com)
>
>

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