From: tamouse mailing lists <tamouse.lists@...>
Date: 2013-01-07T13:26:43+09:00
Subject: Re: ruby 1.9.3p362 ranges as conditions bug?

On Sun, Jan 6, 2013 at 9:09 PM, windwiny <windwiny.ubt@gmail.com> wrote:
> vs = (1..9).to_a
> => [1, 2, 3, 4, 5, 6, 7, 8, 9]
>
> v1 = vs.select { |n| if n==3..n==6 then 1 end }

What do you expect n==3..n==6 to do? That evaluates to a range of
booleans, depending on the value of n:

:001 > a1 = (0..9).to_a
 => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

:002 > a1.map{|n| p n; p n==3; p n==6; p n==3..n==6 }
0
false
false
false..false
1
false
false
false..false
2
false
false
false..false
3
true
false
ArgumentError: bad value for range
	from (irb):14:in `block in irb_binding'
	from (irb):14:in `map'
	from (irb):14
	from /home/tamara/.rvm/rubies/ruby-1.9.3-head/bin/irb:16:in `<main>'

I think rather you might try:

:003 > a2 = a1.select{|n| (3..6).include?(n) }
 => [3, 4, 5, 6]
:004 > a3 = a1.select{|n| (2..16).include?(n) }
 => [2, 3, 4, 5, 6, 7, 8, 9]
:005 > a2 = a1.select{|n| (3..6).include?(n) }
 => [3, 4, 5, 6]

if that is the way you want to go. Better, though, perhaps, to use slices:

:006 > a1[3..6]
 => [3, 4, 5, 6]
:007 > a1[2..16]
 => [2, 3, 4, 5, 6, 7, 8, 9]
:008 > a1[3..6]
 => [3, 4, 5, 6]