From: Derek Taylor <det135@...>
Date: 2008-07-30T12:47:40+09:00
Subject: Re: and and or in case

On Tue, 29 Jul 2008, Pea, Botp wrote:
>Hi All, apologies in advanced if this has been discussed already
>
>why does ruby not compile the following case-when clause if using "and"
>or "or" ? It works if i replace it with "&&" or "||", but i'm not asking
>nor using that, "and/or" are much friendlier.

The operators "and" and "&&" (and likewise "or" and "||") have different
precedence levels.  Things are binding differently than you think that
they should be.

>
>samples,
>
>irb(main):038:0> case
>irb(main):039:1* when 1==1 or 2==2
>irb(main):040:1>    puts "ok"
>irb(main):041:1> end
>SyntaxError: compile error
>(irb):39: syntax error, unexpected kOR, expecting kTHEN or ':' or '\n' or ';'
>when 1==1 or 2==2
>            ^
>(irb):41: syntax error, unexpected kEND, expecting $end
>        from (irb):41
>        from ?:0

Try:
>> case
?> when (1==1 or 2==2)
>>    puts "ok"
>> end
ok
=> nil


>irb(main):050:0> case
>irb(main):051:1* when 1==1 and 2==2
>irb(main):052:1>    puts "ok"
>irb(main):053:1> end
>SyntaxError: compile error
>(irb):51: syntax error, unexpected kAND, expecting kTHEN or ':' or '\n' or ';'
>when 1==1 and 2==2
>             ^
>(irb):53: syntax error, unexpected kEND, expecting $end
>        from (irb):53
>        from :0
>
>thank you and kind regards -botp
>

-Derek.