From: Paul McMahon <pm@...>
Date: 2008-02-14T16:20:07+09:00
Subject: Re: Problem usning 'OR' operator in 'IF' condition?

Apply De Morgan's and you'll see this condition is always true:

@character != 'R' || @character != 'r'

is equivalent to

!(@character == 'R' && @character == 'r')

As @character can never be both 'R' and 'r', @character == 'R' &&  
@character == 'r' is always false, so the statement is

!(false)

which is true.

So your code is equivalent to

if true
   raise " Expected 'R' after 'E' in version Declaration"
end

which is equivalent to

raise " Expected 'R' after 'E' in version Declaration"

You really mean something like

if @character != 'R'  && @character != 'r'
   raise " Expected 'R' after 'E' in version Declaration"
end

Which is better done

if @character !~ /^r$/i
   raise " Expected 'R' after 'E' in version Declaration"
end

If you use regular expressions, then you can probably save yourself a lot  
of unecessary conditionals by writing something like

if some_string !~ /^er$/i
   raise " Expected 'R' after 'E' in version Declaration"
end