# When should one use "and" and "or" **URL:** \ **Category:** Ruby\ **Created:** [February 5, 2010, 5:06am UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948 "2010-02-05T05:06:35Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 5:06am UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/1 "2010-02-05T05:06:35Z")
Hi All, just got hit w the ff > case > when x==1 or x==2 > print “yeoh!” > end > SyntaxError: compile error > (irb):17: syntax error, unexpected kOR, expecting kTHEN or ‘:’ or ‘\n’ > or ‘;’ > when x==1 or x==2 > ^ “or” and “and” both exhibit the behaviour in ruby1.8/1.9. workaround 1 put parens around the condition (not again) 2 replace or/and with ||/&& i believe there are other similar quirks when using “and/or”… has ruby relegated the use of “and/or”…? best regards -botp ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 6:45am UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/2 "2010-02-05T06:45:29Z")
On Feb 4, 9:55 pm, botp [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi All, > > just got hit w the ff > > > case > > when x==1 or x==2 > > print “yeoh!” > > end x = 5 ==\>5 case x when 2,3 p ‘no’ when 4,5 p ‘yes’ end “yes” ==\>nil ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 8:14am UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/3 "2010-02-05T08:14:01Z")
botp wrote: > i believe there are other similar quirks when using “and/or”… > has ruby relegated the use of “and/or”…? No, but it’s essentially inherited from perl. These operators have extremely low precedence, so without parens your statement was being parsed as something like (when x==1) or x==2 I think the typical perl use is something like: open F, “foo” or die “Oops”; If you use || then you need extra params so you don’t get open(F, “foo” || die “Oops”); But if you rely on poetry mode like this it may still trip you up. IMO you’re better off with: a = (some-expr) || (raise “Oops”) a = (some-expr) || raise(“Oops”) ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 4:05pm UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/4 "2010-02-05T16:05:36Z")
On Fri, Feb 5, 2010 at 3:14 PM, Brian C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > No, but it’s essentially inherited from perl. These operators have > extremely low precedence, so without parens your statement was being > parsed as something like > > (when x==1) or x==2 > > I think the typical perl use is something like: > … but brian, i’m still inside the “case” block. can’t ruby sense that? best regards -botp ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 6:56am UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/5 "2010-02-05T06:56:37Z")
On Fri, Feb 5, 2010 at 1:45 PM, w\_a\_x\_man [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: #\> x = 5 #\> ==\>5 #\> case x #\> when 2,3 #\> p ‘no’ #\> when 4,5 #\> p ‘yes’ #\> end of course i know that 😉 im talking about the second type of “case”, eg > case > when x.baz and y.foo > … best regards -botp ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 8:54pm UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/6 "2010-02-05T20:54:46Z")
botp wrote: > but brian, i’m still inside the “case” block. can’t ruby sense that? > And shouldn’t ‘when’ have the same precedence as ‘if’? At least for ‘or’, you can use a comma instead: case when x==1, x==2; puts “1 or 2” end but it doesn’t read as well, and there’s nothing that works like this for ‘and’. ---
**Author:** ![botp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/258eb7/32.png) [@botp](https://www.ruby-forum.com/u/botp)\ **Post date:** [February 5, 2010, 6:06pm UTC](https://www.ruby-forum.com/t/when-should-one-use-and-and-or/182948/7 "2010-02-05T18:06:21Z")
botp wrote: > > �(when x==1) or x==2 > > > > I think the typical perl use is something like: > > … > > but brian, i’m still inside the “case” block. can’t ruby sense that? I agree, but in the absence of a formal grammar you’ll have to look at the implementation.