Going over two interators

ruby-talk
1

I often find that I need to go over two enumerables in parallel. I have
used a little method called ‘both’ for this:

irb
arr1 = [1,2,3,4,5]
–> [1, 2, 3, 4, 5]
arr2 = [6,7,8,9,10]
–> [6, 7, 8, 9, 10]
def both( enum1, enum2 )
enumC = enum2.dup
enum1.each do |e1|
yield e1, enumC.shift
end
end
–> nil
both( arr1, arr2 ) do |a,b|
puts "#{a} : #{b}"
end
1 : 6
2 : 7
3 : 8
4 : 9
5 : 10
–> [1, 2, 3, 4, 5]

It assumes that enum1 is at least at big as enum2.

Is there a way someone can think of that’s more efficient then this?
Namely getting rid of the ‘dup’. Or maybe I’m missing some rubyism that
would make this easier.

TIA,
Michael

2

Michael Garriss wrote:

I often find that I need to go over two enumerables in parallel. I
have used a little method called ‘both’ for this:

irb
arr1 = [1,2,3,4,5]
→ [1, 2, 3, 4, 5]
arr2 = [6,7,8,9,10]
→ [6, 7, 8, 9, 10]
def both( enum1, enum2 )
enumC = enum2.dup
enum1.each do |e1|
yield e1, enumC.shift
end
end
→ nil
both( arr1, arr2 ) do |a,b|
puts “#{a} : #{b}”
end
1 : 6
2 : 7
3 : 8
4 : 9
5 : 10
→ [1, 2, 3, 4, 5]

It assumes that enum1 is at least at big as enum2.

Is there a way someone can think of that’s more efficient then this?
Namely getting rid of the ‘dup’. Or maybe I’m missing some rubyism
that would make this easier.

I just realized that a) my spell checker doesn’t look at the subject
line, and that b) this only works for arrays. How could I make it work
(well) for any enumerable?

Michael

3

Have a look at these:

http://www.rubycentral.com/faq/rubyfaq-5.html#ss5.5

http://www.ruby-lang.org/cgi-bin/cvsweb.cgi/rough/lib/generator.rb?rev=1.6&content-type=text/x-cvsweb-markup
http://rgl.sourceforge.net/files/stream_rb.html

Paul

···

On Thu, Sep 18, 2003 at 08:23:59AM +0900, Michael Garriss wrote:

I often find that I need to go over two enumerables in parallel.

4

In Ruby 1.8, try Enumerable#zip.

-austin

···

On Thu, 18 Sep 2003 08:27:08 +0900, Michael Garriss wrote:

–
austin ziegler * austin@halostatue.ca * Toronto, ON, Canada
software designer * pragmatic programmer * 2003.09.17
* 21.58.04

5

Austin Ziegler wrote:

In Ruby 1.8, try Enumerable#zip.

That’s the one. Thanks to you and the lucky stiff…

Michael