# Irb: 1 & 1 =\> 1, not true huh? I thought 1 & 1 =\> true **URL:** \ **Category:** Ruby\ **Created:** [September 28, 2008, 11:19pm UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719 "2008-09-28T23:19:47Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![mrpete](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ac91a4/32.png) [@mrpete](https://www.ruby-forum.com/u/mrpete)\ **Post date:** [September 28, 2008, 11:19pm UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719/1 "2008-09-28T23:19:47Z")
In irb I did: puts 1 & 1 and get 1 shouldn’t I get true? Bottom line is this: What is Ruby idiom to test for bit mask? Is there a more simple way to write: if session[:permissions] & Permissions::SomeMask == Permissions::SomeMask # user has permission to wash clothes, etc. end TIA, Pete ---
**Author:** ![mrpete](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ac91a4/32.png) [@mrpete](https://www.ruby-forum.com/u/mrpete)\ **Post date:** [September 28, 2008, 11:33pm UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719/2 "2008-09-28T23:33:17Z")
Peter A. wrote: > Permissions::SomeMask > > # user has permission to wash clothes, etc. > > end a && b returns the first false element or the last true element. a & b where a and b are Fixnums does a bit mask like you’re looking for. - Charlie ---
**Author:** ![mrpete](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ac91a4/32.png) [@mrpete](https://www.ruby-forum.com/u/mrpete)\ **Post date:** [September 28, 2008, 11:40pm UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719/3 "2008-09-28T23:40:21Z")
On Sep 28, 4:19 pm, Peter A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Permissions::SomeMask > > # user has permission to wash clothes, etc. > > end > > TIA, You say thanks when nobody has replied, so you are thanking nobody. You should wait till someone has replied before you thank him. Otherwise, he won’t even know that you have read his post; that is very rude and inconsiderate. > Pete # bitwise 254 & 15 ==\>14 # boolean 254 && 15 ==\>15 Only two things are untrue: nil and false. puts “it’s true” if 0 it’s true ==\>nil puts “it’s true” if 254 & 1 it’s true ==\>nil puts “it’s true” if 254 & 1 \> 0 ==\>nil ---
**Author:** ![mrpete](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ac91a4/32.png) [@mrpete](https://www.ruby-forum.com/u/mrpete)\ **Post date:** [September 29, 2008, 10:09am UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719/4 "2008-09-29T10:09:20Z")
> Bottom line is this: What is Ruby idiom to test for bit mask? Is there > a more simple way to write: > > if session[:permissions] & Permissions::SomeMask == > Permissions::SomeMask > > # user has permission to wash clothes, etc. > > end That’s basically right - you can factor this out into your own method if you do it a lot. If you want to test for a single bit, there is Fixnum#[] a = 14 a[0] # 0 a[1] # 1 a[2] # 1 a[3] # 1 a[4] # 0 You’d still have to test for a[2] == 1, since 0 and 1 are both true. However you could use a different representation for your permissions, such as a string containing a single letter for each permission granted. Then: if session[:permissions].include?(“w”) # user has permission to wash clothes end or simply if session[:permissions][“w”] # user has permission to wash clothes end ---
**Author:** ![mrpete](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ac91a4/32.png) [@mrpete](https://www.ruby-forum.com/u/mrpete)\ **Post date:** [September 29, 2008, 5:43am UTC](https://www.ruby-forum.com/t/irb-1-1-1-not-true-huh-i-thought-1-1-true/149719/5 "2008-09-29T05:43:05Z")
Hi, At Mon, 29 Sep 2008 06:19:01 +0900, Peter A. wrote in [ruby-talk:316270]: > puts 1 & 1 > and get 1 > shouldn’t I get true? No. If it were, bit AND operation would be unavailable. > if session[:permissions] & Permissions::SomeMask == > Permissions::SomeMask if (session[:permissions] & Permissions::SomeMask).nonzero?