From: "Guy N. Hurst" <gnhurst@...>
Date: 2002-04-13T15:38:16+09:00
Subject: Re: not vs !, and vs &&

Sean Chittenden wrote:
> ...
> > Can someone enlighten me?  How, and where, are these implemented?
> > Why the difference in behavior?
> 
> > Is puts true and (!true)
> >
> > intertpreted as
> >  (puts true) and (!true)
> >
> > I tried this
> >  puts (true and (!true) )
> 
> That seems like a bug...
> 

Not a bug. 

p. 508, "The Ruby Way":
"... if parentheses are used near a method, then Ruby will
associate them with the method and expect an argument list inside.
An expression is a valid argument."

'puts' is a method, so it adapts the parentheses as its own syntax 
for parameters.

Meanwhile, 'true' is an expression and '!true' is an expression, but
combining them with 'and' forms a statement.
(combining them with '&&' would have formed another expression directly)

You must enclose a ruby statement in parentheses to form a ruby expression.

puts( (true and !true) )
puts( (not true) )

This demonstrates the slight difference between a ruby 'statement' 
and a ruby 'expression'. Statements must be enclosed in parentheses
to form an expression, which is required for using them as an argument.


Guy N. Hurst