From: Eustaquio 'TaQ' Rangel <eustaquiorangel@...>
Date: 2008-06-04T04:49:55+09:00
Subject: About 1.8.7 Array#map! without a block

Hi there.

I was wondering how to use Array#map! with a block. On the usual way, we
have

irb(main):001:0> a = [1,2,3]
=> [1, 2, 3]
irb(main):002:0> a.map! {|i| i*2}
=> [2, 4, 6]

Now with 1.8.7 we have:

irb(main):003:0> e = a.map!
=> #<Enumerable::Enumerator:0xb7db015c>
irb(main):004:0> e.next
=> 2
irb(main):005:0> a
=> [#<Generator:0xb7d9b9dc @queue=[4],
@cont_endp=#<Continuation:0xb7d9b1a8>, @index=1,
@block=#<Proc:0xb7da7ffc@/usr/local/lib/ruby/1.8/generator.rb:71>,
@cont_yield=#<Continuation:0xb7d9aed8>, @cont_next=nil>, 4, 6]
irb(main):006:0> a.size
=> 3

I got an Enumerable::Enumerator with a.map! and then the first call to
e.next returned me the first "a" element, 2. Ok, two questions:

1 - Since I created the Enumerable::Enumerator with map!, I presume it's
used on some way to change the elements on "a", so what should I use
with e.next to change the value, say, multiplying by 2 as on the first
case and have a [4,8,12] array on the end?

2 - Why I get a Generator on "a" elements when I just call e.next? The
cause it's what I'm missing to use with next, as asked on the first
question?

Thanks!