From: "Carlo E. Prelz" <fluido@...>
Date: 2012-12-08T16:29:42+09:00
Subject: Re: if n belongs to set a and m belongs to set b repeat some steps, How?

	Subject: if n belongs to set a and m belongs to set b repeat some steps, How?
	Date: Sat 08 Dec 12 02:05:33PM +0900

Quoting zubair a. (lists@ruby-forum.com):

> We can do so in java and similar languages like:
> 
> for (int i=0, int j=3; i<=2 && j<=5;i++,j++){
>   do some repetive task until the condition becomes false...
> }
> 
> how to keep these two conditions based on two different sets(suppose two
> arrays whose indexes can be used as i and j) in condition block??

The simplest way is just to unroll the C construct:

i=0
j=3
while(i<=2 && j<=5)
 ..
 ..
 ..
 i+=1
 j+=1
end

It is less neat, I am afraid, but it works the same way.

I often use for loops like that in C, but when I write in Ruby I know
I must express the algorithm in a different way. Ruby loops manage
only one variable. How I do it depends on the case. In your example,
for example, the loop runs 3 times (unless you modify the loop
variables within the loop itself), and j is always equal to i+3. Thus
I could do

3.times do |i|
 ..
 ..
end

and inside the loop, when in need of the 'j' value, I'd instead use
'i+3'. 

Carlo

-- 
  *         Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as             che bisogno ci sarebbe
  *               di parlare tanto di amore e di rettitudine? (Chuang-Tzu)