From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-03-20T14:30:08+09:00
Subject: Re: C(++) For Loop Equivalents

Raj Sahae wrote:
> studlee2 wrote:
>> What is the most efficient way in Ruby to create a conditional loop in
>> Ruby that looks like this in C(++):
>>
>> for(int i=0; i*j/2<maxNum; i++)
>> {
>>   //cool method stuff
>> }
>>
>>
>> I was looking at the .upto() method but it doesn't like the comparison
>> operator :-/
>>
>> Thanks
> Why not just do:
> ((maxNum*2)/(i*j)).times do |n|
>    #cool method stuff
> end
> 

He would need to initialize i before your code as it could be any value, 
not just 0.  By the same token the increment could be any number, not 
just 1.
A further problem with your method is that the loop is executed until 
i*j/2 is greater than maxNum.  As you don't know if the loop somehow 
modifies the value of j you can not optimize it out.  A simple example 
would be where the program reads some numbers from a file and adds them 
to j.  i is incremented by one each time a number is read.  You want the 
program to exit when i*j/2 is larger than maxNum.