From: "Jan E." <jan.e@...>
Date: 2012-03-19T02:21:21+09:00
Subject: Re: why no decreasing enumerations?

Hi,

I think you misunderstand the purpose of ranges. They aren't meant to be 
ordered lists but rather some kind of abstract interval (like in 
mathematics). You can check if a specific object is in the range, but 
you may not even be able to enumerate all the elements of the range.

For example, try
(1.0 .. 5.0).each {|el| puts el}
This raises a TypeError: "can't iterate from Float"

Of course, you *can* iterate over some ranges (if the endpoints have a 
succ method). But then the elements will simply be put out in the most 
obvious way: from low to high. The range itself doesn't imply a certain 
order.

If you actually want to count up/down from some integer to another, you 
should use an appropriate data structure like an enumerator:

a, b = rand(20), rand(20)
list = if a <= b
  a.upto b
else
  a.downto b
end

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