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ROUND TABLE! :)
Seems we're at it, already? Take the integer patch in there, too. Merge the two issues, into "Number storage models in Lua" or something.
We should be able to solve out a way, which allows compile-time number processing schemes to be easily swapped, without actual patching of the Lua internals. Many macros there are, are already pointing in this direction (maybe intentionally?).
I would _really_ like to have int32/64 patching merge with Lua, but placing it within the core source as now may well be the wrong approach. Would be better, to keep the arithmetic c files separate, and let the core find them via configured macros. 

Getting too deep now, the Rest in Venlo.
HEY: Someone please take a videocam; the round tables should be available online, at least edited! :) 

-asko


Andy Stark kirjoitti 24.8.2006 kello 16.07:


Lua list <lua@bazar2.conectiva.com.br> on Thursday, August 24, 2006 at
11:00 +0000 wrote:

Since bignums are part of Common Lisp they deserve to be on the
roadmap for Lua.  Don't see why we should be wedded to a radix 10
implementation though.
The main advantage of decimal arithmetic is that it behaves exactly like paper arithmetic. If you do a sum like 0.99 + 0.01 you get exactly 1 as 
the result instead of merely getting the result of adding the binary
approximations of 0.99 and 0.01. I think we would all save ourselves a few 
bugs by adopting BCD, but it is of most value to non-professional
programmers who wouldn't easily understand why comparisons sometimes don't 
work. (For "non-professionals", think about most users of VoodooPad,
Lightroom, games, etc). The ECMAScript 4 (ie, JavaScript 2.0) proposal
contains a recommendation to support decimal arithmetic, optionally as the 
default numeric type:-

	http://developer.mozilla.org/es4/proposals/decimal.html

Brendan Eich gave a presentation about the future of JavaScript in May
2006 where he claims that arithmetic inaccuracies are the most duplicated 
bug in the Mozilla project:-

(Go to page 38 at
	http://ajaxian.com/downloads/presentations/eich-ajax-experience-2006/
)
Also, as has already been mentioned, some financial software is legally required to use decimal arithmetic to minimise the chance of fraud. The quirky but clever old language of Rexx has always used decimal arithmetic as its only numeric type and Python has recently added a decimal module to 
its standard library.

BCD can be converted to and from a decimal textual representation very
quickly and without error. This means that it is often actually faster
than binary for programs that do text processing but relatively little
arithmetic (think of, say, numeric attributes in an HTML-generating
script). Perhaps this might also slightly speed up the compilation of
source files written in Lua, but I'm not too sure about that.

I think BCD feels like a natural Lua thing and in cases where it's not
efficient enough it's easy to replace it with floats or integers. And it 
will give you something to talk about at the round table ;-)

&.
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