From: Robert Klemme <shortcutter@...>
Date: 2008-07-30T00:08:20+09:00
Subject: Re: and and or in case

2008/7/29 Peņa, Botp <botp@delmonte-phil.com>:
> From: Ben Brightwell [mailto:neogia4@gmail.com]
> # The way I see it (and also the way I practice it today) is to always
> # always always use "&&" or "||" over "and" or "or", respectively.
> # The words "and" and "or" are lower in the order of operators than the
> # symbols "&&" and "||". This is intentional for beginner
> # programmers to be able to "read" the code rather than work out the
> # logic of  the code.
>
> Ben thanks, but i'm not convinced. It still does not answer why it is not allowing in case-when clause yet allowing it in if-elsif,

The answer is the precedence defined into the syntax.

15:13:04 oz-27416_Failed_to_lock_accounts$ ruby -c <<XXX
> case
> when a > b || c < d
> puts 1
> end
> XXX
Syntax OK
17:05:28 oz-27416_Failed_to_lock_accounts$ ruby -c <<XXX
> case
> when a > b or c < d
> puts 1
> end
> XXX
-:2: syntax error, unexpected kOR, expecting kTHEN or ':' or '\n' or ';'
when a > b or c < d
             ^
-:4: syntax error, unexpected kEND, expecting $end
17:06:46 oz-27416_Failed_to_lock_accounts$


> sample,
>
> if 1==1 and 2==2
>  p "ok"
> end
> "ok"
> #=> nil
>
> case
> when 1==1 and 2==2
>  p "ok"
> end
> SyntaxError: compile error
> (irb):5: syntax error, unexpected kAND, expecting kTHEN or ':' or '\n' or ';'
> when 1==1 and 2==2
>             ^
> (irb):7: syntax error, unexpected kEND, expecting $end
>        from (irb):7
>        from :0
>
> arggh, i love using case-when and and/or and now both do not work together?? quite a surprise to me there.

Note though that you can have your "or" differently in a "case" expression:

17:06:46 oz-27416_Failed_to_lock_accounts$ ruby -c <<XXX
> case
> when a > b, c < d
> puts 1
> end
> XXX
Syntax OK
17:08:01 oz-27416_Failed_to_lock_accounts$

And you can at least do

17:08:01 oz-27416_Failed_to_lock_accounts$ ruby -c <<XXX
> case
> when ( a > b and c < d )
> puts 1
> end
> XXX
Syntax OK


Kind regards

robert

-- 
use.inject do |as, often| as.you_can - without end