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From: prindle@NADC.ARPA
Newsgroups: comp.sys.cbm
Subject: C Power 128 floating point to integer conversion bug
Message-ID: <5365@rutgers.rutgers.edu>
Date: Thu, 29-Oct-87 20:51:41 EST
Article-I.D.: rutgers.5365
Posted: Thu Oct 29 20:51:41 1987
Date-Received: Wed, 4-Nov-87 03:38:31 EST
Sender: daemon@rutgers.rutgers.edu
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From: prindle@nadc.arpa (Frank Prindle)

I have finally figured out what causes C Power 128 to incorrectly convert
floating point values to integers (signed), and this bug could easily explain
all kinds of miscellaneous problems with floating point when using this
compiler.  The problem is in library file "float1.obj".  It revolves around
a BASIC ROM routine used to do the conversion; the library assumes this BASIC
routine returns it's values in the A and Y registers, but it doesn't; rather
it returns them in the floating point accumulator in bank 0.  Furthermore,
even when the return value is fetched from the correct place, the routine
only operates correctly if the floating point number has first had it's
fractional part removed (BASIC INT function) by truncating toward -infinity.
When I get a chance, I will post both the fixed source and the object code
for "float1.obj".  The source can be assembled by the Rinfret/Zarling C Power
assembler.  In any case, once you have replaced "float1.obj" on a copy of your
library, conversions from float to (signed) integer will work much, much
better.

Remember, this relates to C Power *128* only, not the 64 version.  The 64
version works correctly because a different BASIC ROM routine is used.
Sincerely,
Frank Prindle
Prindle@NADC.arpa