pow operator miscalculation

[J. David Bryan]

On 10 Sep 2001, at 9:57, da Silva, Joe wrote:

> I'm not good on the jargon, but is "-2" really a unary "-" and
> a number (2), or is "-2" a number in itself (ie. the sign is not
> an operator)?

The Extended Pascal standard, section 6.8.1, "Expressions, General," says 
that the expression "-2" is a simple-expression, which is defined as a sign 
followed by a term.  So "-" is the sign, and "2" is the term.  The standard 
therefore treats any expression with a leading sign as a unary operator 
applied to an unsigned expression.

To continue, "-2 pow 2" is parsed as the sign "-" and the term "2 pow 2".  
The term is parsed as a factor, which is defined as a primary, followed by 
an exponentiating-operator (in this case, "pow"), followed by another 
primary.  "2" is a primary because primaries may be unsigned-constants.


> This is what Maurice suggested in his second posting, and is the
> natural/intuitive interpretation of "-2". 

Unfortunately, "intuitive interpretations" don't count when a standard says 
otherwise....  :-)

                                      -- Dave