🚀 go-pugleaf

In article  <L-2A3G2@xds13.ferranti.com> Peter da Silva writes:

]But if you don't know that y is complex, you don't know if "y <= 0" is
]legal or not...

If you don't know the length of A, you don't know whether "A[i]" is
legal or not.  So?  You should know the length of A and you should
know the type of y.  In someone elses code, if you see "y <= 0",
then you can assume that y is not complex.  In you own code, if you
know that y is not complex you can write "y <= 0".  There is no
ambiguity.

]with this in mathematics is everyone has had a bunch of Fortran-style'
]default typing rules programmed into their head in college.

No, the reason you can get away with this in math is that everyone who
has a clue knows that you can't compare magnitudes of complex numbers,
so if you are comparing magnitudes, the numbers must not be compex.
This is a trivial logical inference:

(1) y is complex implies "y <= 0" is not meaningful
(2) "y <= 0" is meaningful
therefore
(3) y is not complex

There is nothing sloppy or ambiguous about this reasoning.
--
					David Gudeman
gudeman@cs.arizona.edu
noao!arizona!gudeman