Forum: Ruby ruby 1.9.3p362 ranges as conditions bug?

Hello,

  I am test this has a problem,

ruby -v
ruby 1.9.3p362 (2012-12-25 revision 38607) [x86_64-darwin12.2.1]


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 }
=> [3, 4, 5, 6]

v2 = vs.select { |n| if n==2..n==16 then 1 end }
=> [2, 3, 4, 5, 6, 7, 8, 9]

v3 = vs.select { |n| if n==3..n==6 then 1 end }
=> [1, 2, 3, 4, 5, 6]

v1 and v3 use some condition , return value is different.

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]

On Mon, 07 Jan 2013 05:26:43 +0100, tamouse mailing lists 
<tamouse.lists@gmail.com> wrote:

> 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:

These are so-called flip-flops, and a valid though obscure feature of 
Ruby. Here's a nicer test case:

irb(main):001:0> (1..100).each do |i|
irb(main):002:1*   puts i if i==42..i==45
irb(main):003:1> end
42
43
44
45

windwiny, I wasn't able to replicate your results on ruby 1.9.3p0 
(2011-10-30) [i386-mingw32]. v1 and v3 both gave the same (first) 
result.

Run code on irb, pry has different result, write code to file, run from
file, that return same result. Maybe it is (1.9.3p362)irb's bug.

2013/1/7 Matma Rex <matma.rex@gmail.com>

Hi,

2013/1/7 windwiny <windwiny.ubt@gmail.com>:
>
>
>
Hi,

2013/1/7 windwiny <windwiny.ubt@gmail.com>:
> Run code on irb, pry has different result, write code to file, run from
> file, that return same result. Maybe it is (1.9.3p362)irb's bug.
>
I confirmed this bug also occurred on ruby trunk.
I filed a bug issue on behalf of you.
https://bugs.ruby-lang.org/issues/7671

Regards,

Park Heesob

On Mon, Jan 7, 2013 at 12:01 AM, Matma Rex <matma.rex@gmail.com> wrote:
>>
> 42
> 43
> 44
> 45
>

I really do not understand how this works. I can see what it produces, 
but why?

Hi,

2013/1/8 tamouse mailing lists <tamouse.lists@gmail.com>:
>>>
>> irb(main):003:1> end
>> 42
>> 43
>> 44
>> 45
>>
>
> I really do not understand how this works. I can see what it produces, but why?
>
You can see a detailed explanation at
http://ruby.about.com/od/convolutedconstructions/s...

Regards,

Park Heesob