From: Justin Collins <collinsj@...>
Date: 2006-10-30T17:52:28+09:00
Subject: Re: Using "not" in compound conditions

Peter Lynch wrote:
> Hi
>  I am still a beginner at Ruby, and have just arrived at this in my 
> learning curve.
>
>  I would like to code
>      not(condition1) && not(condition2)
>  This is accepted in irb -
>      not(condition1) && condition2
>  but this produces a syntax error
>      condition1 && not(condition2)
>
>  I do not get it (obviously). I do not even know what to ask in reply -
>  How do I code a compound condition, without introducing extra wrappers 
> like -
>      (not(condition1)) && (not(condition2))
>
>  Regards
>  Peter
>   

"&&", "||", and "!" have higher precedence than "and", "or" and "not" - 
so it can be tricky.

However, you could do:

(not condition1) && (not condition2)

or, not mixing the two:

not condition1 and not condition2

Of course, it's best to be clear, and parentheses help that. Hope that 
helps.

-Justin