From: Robert Klemme <shortcutter@...>
Date: 2011-07-25T01:57:14+09:00
Subject: Re: Better name for #zip_with

On Sun, Jul 24, 2011 at 8:24 AM, Christopher Dicely <cmdicely@gmail.com> wrote:
> On Mon, Jul 18, 2011 at 10:25 AM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> Thomas Sawyer wrote in post #1011313:
>>> On Jul 17, 10:36pm, John Feminella <jo...@bitsbuilder.com> wrote:
>>>> How about #zip_and_map? Notice that:
>>>>
>>>> > a.zip_with(b) { |c, d| ... }
>>>>
>>>> is the same as the result of
>>>>
>>>> > a.zip(b).map { |c, d| ... }
>>>
>>> Ah, right. `#zip_map` would makes sense then. But per your last post,
>>> I think I may override #zip itself.
>>
>> Not sure whether I find this a good idea.  Reason: #map has overhead of
>> creating a new Array with the same length as the input.  That should not
>> be the default behavior IMHO.
>
> So, don't do that; just return an Enumerator that returns the
> successive results of applying the given block to the elements that
> would be returned by the Enumerator that would be returned by the
> non-block form of #zip.

What exactly do you mean?  #to_enum does not honor a block:

irb(main):001:0> a=5.times.to_a
=> [0, 1, 2, 3, 4]
irb(main):002:0> b=a.to_enum(:map) {|x|x*2}
=> #<Enumerator: [0, 1, 2, 3, 4]:map>
irb(main):003:0> b.to_a
=> [0, 1, 2, 3, 4]

Did you mean Generator?

irb(main):012:0> b=Enumerator.new {|y| a.each {|x| y << x*2}}
=> #<Enumerator: #<Enumerator::Generator:0x106afc60>:each>
irb(main):013:0> b.to_a
=> [0, 2, 4, 6, 8]

With #zip

irb(main):014:0> b=a.dup
=> [0, 1, 2, 3, 4]
irb(main):015:0> i=Enumerator.new {|y| a.zip(b){|m,n| y << m - n} }
=> #<Enumerator: #<Enumerator::Generator:0x1066d248>:each>
irb(main):016:0> i.to_a
=> [0, 0, 0, 0, 0]

Kind regards

robert

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