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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Jay, <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I think the documented intent in Modula-3 is that the programmer
<u>should</u> write his code under the premise that any operation that could
produce an overflow should be rewritten so as to avoid that problem.
Further, that the implementation may or may not actually check for this
condition, but to <b><u>rely</u></b> on it working a certain way (e.g., silent
wrap) would be wrong. Further, if FloatMode were implemented, it would be
possible to force the overflow check on.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This situation does not prohibit a programmer from writing
something that could produce overflow, and the fact that on some
implementations overflow is not checked is considered ok for performance
reasons. It is just that if the programmer were to rely on silent wrap, this
reliance is NOT supported by the language and at some point will probably cause
a checked runtime error.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Indeed, folks often turn on extra checking during program
testing to find as many programming faults as possible, then turn off the extra
checking for production/delivery code to gain performance. So Modula-3 as
a language supports this concept, though not all implementations may provide
the ability to turn certain checks on or off.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I agree that lumping the integer overflow control into an
interface named “FloatMode” makes it a bit hard to find since “FloatMode”
would make one think that the interface deals only with floating point.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>So, in Modula-3 a good programmer will add appropriate logic to
prevent overflow by explicitly coding wrap-around or using some other method
appropriate to the task at hand. A sloppy programmer won’t care and
his code will eventually break. See the comments about long-lived
readers/writers for an example.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Regards,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Randy<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> jayk123@hotmail.com
[mailto:jayk123@hotmail.com] <b>On Behalf Of </b>Jay K<br>
<b>Sent:</b> Monday, January 11, 2010 11:55 PM<br>
<b>To:</b> Tony; m3devel<br>
<b>Subject:</b> [M3devel] FloatMode<o:p></o:p></span></p>
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</div>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
12.0pt;margin-left:.5in'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif"'>I
thought FloatMode was only related to floating point.<br>
So I looked:<br>
<br>
"IntOverflow" = an integer operation produced a result
whose<br>
absolute value is too large to be represented.<br>
<br>
"IntDivByZero" = integer "DIV" or
"MOD" by zero.<br>
\end{quote}<br>
<br>
<br>
This part of it should be easy to implement for all architectures.<br>
The entire thing probably isn't too difficult either on many platforms either.<br>
<br>
However...I was surprised by this.<br>
I thought the real "intent" in Modula-3 to not have this be
configurable<br>
and endeavor for overflow and divide by zero to always immediately<br>
raise an exception? The only "out" is that it might not get
implemented on some platforms for some reason?<br>
<br>
For the floating point stuff:<br>
<br>
Probably like other per-platform code, this should be done in #ifdefed C.<br>
<br>
<a href="http://msdn.microsoft.com/en-us/library/e9b52ceh(VS.80).aspx">http://msdn.microsoft.com/en-us/library/e9b52ceh(VS.80).aspx</a><br>
<a href="http://kernel.org/doc/man-pages/online/pages/man3/fetestexcept.3.html">http://kernel.org/doc/man-pages/online/pages/man3/fetestexcept.3.html</a><br>
etc.<br>
<br>
- Jay<o:p></o:p></span></p>
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