From: David Vallner <david@...>
Date: 2006-02-09T11:27:38+09:00
Subject: Re: Formatting Numbers

Dňa Štvrtok 09 Február 2006 03:11 Logan Capaldo napísal:
> On Feb 8, 2006, at 8:43 PM, HH wrote:
> > This has got to be simple but I checked the PickAxe and Google to
> > no avail.
> > My guess is that I'm looking for it in terms that don't make sense.
> >
> > Anyway...
> >
> > I have a fixnum:
> >
> > a = 1000
> >
> > I would like to output it with a comma, such as "1,000". Is there a
> > formatting class or something I can use something along these lines
> > (thinking from my Java background):
> >
> > Formatter f = Formatter.new("N0")
> > puts f(a)
> >
> > Any help appreciated.
> >
> > Thanks,
> > Hunter
>
> I dunno know about some kind of builtin format object (I imagine
> maybe the right incantation of sprintf could do it) but heres a
> method (kinda long for what it is, theres probably some regex to do
> it in one fell swoop):
>
> % cat commify.rb
> require 'enumerator'
> def commify(num)
>    str =  num.to_s
>    a = []
>    str.split(//).reverse.each_slice(3) { |slice| a << slice }
>    new_a = []
>    a.each do |item|
>      new_a << item
>      new_a << [","]
>    end
>    new_a.delete_at(new_a.length - 1)
>    new_a.flatten.reverse.join
> end
>
> p commify(1000)
> p commify(100)
> p commify(1_000_000)
> p commify(1024)
>
> % ruby commify.rb
> "1,000"
> "100"
> "1,000,000"
> "1,024"

Hmm, I was in the middle of writing precisely this sort of hack as this 
arrived. That said, much better job here. The #each_slice comes from the 
enumerator library? I should really learn to use that one...

That said, I'm almost sure you can golf that thing down a bit. How about:

	require 'enumerator'
	def commify(num)
		str =  num.to_s
		a = []
		str.split(//).reverse.each_slice(3) { |slice| a << slice }
		a.reverse.collect{|i| i.reverse.join}.join(",")
	end

	p commify(1000)
	p commify(100)
	p commify(1_000_000)
	p commify(1024)

Now if only we directly had a method to slice an Array into an Array of 
slices, the whole thing could turn into a one-liner. Which I hate, but in a 
good way.

David Vallner