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12-Feb-87 18:03:34-PST,1776;000000000001
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Date: Thu 12 Feb 87 17:28:40-MST
From: "Nelson H.F. Beebe" <[email protected]>
Subject: Floating-point fixup handler
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X-US-Mail: "Center for Scientific Computation, South Physics, University of Utah, Salt Lake City, UT 84112"
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Three possibilities suggest themselves for a KCC
floating-point fixup handler. The first is Ralph Gorin's
book on TOPS-20, and the sources are probably online at
SCORE or LOTS. The second is Chuck Hedricks Pascal
compiler, for which we all have sources; routine SETARITH in
the Pascal runtime library is a good place to start looking.
The third source is FOROxx.EXE, the FORTRAN run-time system,
for which I have sources, having been a field test site for
versions 6, 7, and 10. This source of course would be
"stealing".
The job needs to be done carefully, including having support
for G-floating (we have users who would really like to call
FORTRAN math library code from C; it was the lack of
floating-point fault handling in PCC-20 which prevented this
from ever working successfully).
It would be interesting to use the fixup handler to
implement gradual underflow, a la IEEE arithmetic. It would
be possible, though not uniformly so, to fake an infinity
and a Nan too; unfortunately, the -20 has no reserved
operand floating-point pattern to do this with complete
success.
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