# Storing boolean flags in numbers **URL:** \ **Category:** Ruby\ **Created:** [May 23, 2007, 12:43pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871 "2007-05-23T12:43:07Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 12:43pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/1 "2007-05-23T12:43:07Z")
I might sound completely dumb asking this question, but well, I’ll risk it anyway! Some years ago I read about using a single number as a mechanism for storing flags (on/off values) in a Java magazine. By setting the bits in a number to either 0 or 1 you could store enormous amounts of boolean values in a single number. An example. I have three flags: Flag1 Flag2 Flag3 (The following byte sequences are written from the right) Flag1 = true Flag2 = false Flag3 = false gives: 001 =\> 1 Flag1 = false Flag2 = true Flag3 = true gives: 110 =\> 6 Flag1 = true Flag2 = false Flag3 = true gives: 101 =\> 5 In the magazine they used some sort of combination of AND and OR and XOR and stuff like that to get the different values. Would there be an easy way to do this in Ruby? How would one implement a thing like this? I basically just need a way to read the different values. I’ll try to extend it myself so I can read any given number of flags myself. Just need to understand how to read and set the flags! Best regards Sebastian ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 12:46pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/2 "2007-05-23T12:46:41Z")
In message [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid), Sebastian probst Eide writes: > I basically just need a way to read the different values. I’ll try to > extend it myself so I can read any given number of flags myself. Just > need to understand how to read and set the flags! You’re looking for “bitwise operators”. Experiment with “5 & 4” or “1 | 4”. -s ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 12:51pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/3 "2007-05-23T12:51:23Z")
> You’re looking for “bitwise operators”. > > Experiment with “5 & 4” or “1 | 4”. > > -s > Great, > thanks ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 1:16pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/4 "2007-05-23T13:16:06Z")
> p 5[2] > Wow! This is great! But is there a way to set flags this way to? Say I have: flags = 0b010110010 checking flag 6 is easy enough flags[6] =\> 0 But how could I easily set flag 6 to 1? flags[6] = 1 doesn’t work obviously… ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 1:10pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/5 "2007-05-23T13:10:48Z")
Hi, At Wed, 23 May 2007 19:46:01 +0900, Peter S. wrote in [ruby-talk:252673]: > Experiment with “5 & 4” or “1 | 4”. p 5[2] ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 1:36pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/6 "2007-05-23T13:36:50Z")
On 23.05.2007 13:16, Sebastian probst Eide wrote: > > p 5[2] > > Wow! This is great! But is there a way to set flags this way to? > > Say I have: > flags = 0b010110010 > > checking flag 6 is easy enough > flags[6] =\> 0 > But how could I easily set flag 6 to 1? > flags[6] = 1 doesn’t work obviously… Set and reset: irb(main):001:0\> flags = 0b010110010 =\> 178 irb(main):002:0\> flags[6] =\> 0 irb(main):003:0\> flags |= 1 \<\< 6 =\> 242 irb(main):004:0\> flags[6] =\> 1 irb(main):005:0\> flags ^= flags[6] \<\< 6 =\> 178 irb(main):006:0\> flags[6] =\> 0 See also [http://raa.ruby-lang.org/project/bitset/](http://raa.ruby-lang.org/project/bitset/) Kind regards robert ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [May 23, 2007, 2:03pm UTC](https://www.ruby-forum.com/t/storing-boolean-flags-in-numbers/104871/7 "2007-05-23T14:03:04Z")
Great! Thanks Robert