Am 20.10.2011, 08:02 Uhr, schrieb Russel Winder <rus...@russel.org.uk>:
On Wed, 2011-10-19 at 23:36 -0400, dsimcha wrote:
On 10/19/2011 11:27 PM, Marco Leise wrote:
> And real can be used without protability problems on PowerPC or ARM?
Yes, it's just that they may only give 64 bits of precision. Floating
point is inexact anyhow, though. IMHO the fact that you may lose a
little precision with very large longs is not a game changer.
This is not convincing.
One of the biggest problem is software development is that computers
have two systems of hardware arithmetic that are mutually incompatible
and have very different properties. Humans are taught that there are
abstract numbers that can be put into different sets: reals, integers,
naturals, etc.
There are already far too many programmers out there who do not
understand that computer numbers have representation problems and
rounding errors.
Another issue:
sqrt ( 2 )
sqrt ( 2.0 )
sqrt ( 2.0000000000000000000000000000000000000000 )
actually mean very different things. The number of zeros carries
information.
Summary, losing precision is a game changer. This stuff matters. This
is a hard problem.
Sure it matters, but performance also matters. If I needed the precision
of a real, I would make sure that I give the compile the right hint. And
adding zeros doesn't help. The representation is mantissa and exponent and
your three examples would all come out the same in that representation. :)
Is this really a real life problem, or can we just go with any solution
for sqrt(2) that works (int->double, long->real) and leave the details to
the ones who care and would write sqrt(2.0f) ?
