Mail Archives: djgpp/1996/02/21/17:09:39
In article <271654446E1 AT fs2 DOT mt DOT umist DOT ac DOT uk>,
A.Appleyard <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk> wrote:
> I am sick of program runs being hostage to one stray floating point overflow.
> What I want is one or both of (1) Being able to tell the PC to carry on
> regardless if overflow happens, (2) Being able to tell the PC to go to such
> and such an address if overflow happens.
And what do you intend to do in (2) if you get there (except to terminate
the program)?
If you're using a coprocessor (80x87, or a 486DX or Pentium), the
coprocessor can be programmed for this. You can tell the coprocessor
to not generate interrupts when f.p. overflows etc happens, and instead
return some approproate value. Division by zero will return "infinite",
dividing zero by zero, or multiplying infinite by zero, will return
"indefinite", and attempting things like the sqrt or log of a negative
number, or asin/acos of numbers above +1.0 or below -1.0, will return
"not-a-number". The coprocessor can continue doing operations on these
special representations -- for instance dividing by "infinite" will
produce zero, most operations on "indefinite" will produce another
"indefinite", and any operation on "not-a-number" will produce another
"not-a-number".
For details, check Intel's, or someone else's, documentation for the
80x87 coprocessor.
--
----------------------------------------------------------------
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
Grev Turegatan 40, S-114 38 Stockholm, SWEDEN
e-mail: pausch AT saaf DOT se psr AT home DOT ausys DOT se
- Raw text -