From: "David A. Black" <dblack@...>
Date: 2005-03-31T04:38:07+09:00
Subject: Re: beginner iterators question

Hi --

On Thu, 31 Mar 2005, Jeff Fry wrote:

> Hi,
>
> I am brand new to ruby and liking it so far - particularly the watir test 
> libraries.

Welcome :-)
> I am comfortable with the Java for loop syntax (i=0, i<4, i++) and 
> haven't found something in ruby that feels as elegant, particularly when I 
> want to use an increasing value i within the loop. Here's an example (with my 
> limited ruby)
>
>       i=0
>       0.upto(3) do                                         puts 'try number 
> ' + i.to_s                   i = i+1                                     # is 
> there a more elegant way to do i++ ?
>       end
>
> I am guessing that ruby provides a more elegant way to do the above. I would 
> love recommendations both on how to iterate when I want to use the changing 
> value of the iterator in the loop, and how in ruby to do i++. Is there a way 
> with upto() to use the current value during iteration? or another iterator 
> where that is possible without needing to define i seperately?

You need to pass an argument to your code block:

   0.upto(3) do |i| puts "try number #{i}" end

or you could do:

   4.times {|i| puts "try number #{i}" }  # here I've used the {} block
 					 # syntax, which is pretty
 					 # common for same-line blocks

or even:

   puts (0..3).map {|i| "try number #{i}" }

(iterating over a range, which you can do if the range uses integral
values)

For general-purpose incrementing, there's:

   i += 1

(There's no ++ in Ruby because numbers are immediate values.  So this:

   i = 0
   i++

would actually be the same as:

   0++

which would cause all sorts of trouble :-)


David

-- 
David A. Black
dblack@wobblini.net