From: Brian Candler <B.Candler@...>
Date: 2010-09-01T18:16:41+09:00
Subject: [ruby-core:31992] Parsing of 'not'

Is the following intentional?

>> puts(not 3 < 4)
SyntaxError: compile error
(irb):4: syntax error, unexpected kNOT, expecting ')'
puts(not 3 < 4)
        ^
(irb):4: syntax error, unexpected ')', expecting $end
	from (irb):4
	from :0

However, it works with double parentheses:

>> puts((not 3 < 4))
false

Tested with: ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]

I stumbled across this when trying to do:

  assert not a < b

Regards,

Brian.

P.S. In any case it seems to be difficult to use the value of 'not', unless
you add parentheses.

>> not 3 < 4
=> false
>> a = not 3 < 4
SyntaxError: compile error
(irb):2: syntax error, unexpected kNOT
a = not 3 < 4
       ^
	from (irb):2
	from :0
>> a = (not 3 < 4)
=> false

I realise that 'and' and 'or' have precedence lower than assignment, but
'not' is a unary operator.  Perl has no problem with the following:

perl -e 'print not 4 < 3'            # prints 1
perl -e '$a = not 4 < 3; print $a'   # prints 1