From: "Mauricio Fernández" <batsman.geo@...>
Date: 2002-08-22T04:27:06+09:00
Subject: Re: Puzzeled by Range object

On Thu, Aug 22, 2002 at 01:03:07AM +0900, ts wrote:
> >>>>> "R" == Robert McGovern <duemoko@bigfoot.com> writes:
> 
> R> However the second, simply printed nothing. Am I wrong to expect that a 
> R> range can work for both up and down?
> 
>  Range can work only up.
> 
>  Except for Fixnum and Numeric, Range#each use #succ and it's difficult to
>  define the inverse of #succ for any type
> 

What about this?


batsman@kodos:~/src/rubylang$ cat myrange.rb


class Range
 def each
	if (first <=> last) == -1
		# proceed in normal order
		a = first
		while ( a != last )
			yield a
			a = a.succ
		end
		yield last unless exclude_end?
	else
		# reverse!
		a = last
		a = a.succ if exclude_end?
		while ( a != first )
			yield a
			a = a.succ
		end
	end
 end
end

l = [	"(1..3).each { |x| puts x }",
	"(-3..1).each { |x| puts x }",
	"(1...3).each { |x| puts x }",
	"(-3...1).each { |x| puts x }"	]

l.each { |x| puts "Executing #{x}"; eval x }
batsman@kodos:~/src/rubylang$ ruby myrange.rb
Executing (1..3).each { |x| puts x }
1
2
3
Executing (-3..1).each { |x| puts x }
-3
-2
-1
0
1
Executing (1...3).each { |x| puts x }
1
2
Executing (-3...1).each { |x| puts x }
-3
-2
-1
0
batsman@kodos:~/src/rubylang$
Script terminado (Wed Aug 21 21:27:04 2002
)

It will surely break something, anybody cares to test it?

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