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- Subject: Re: Possible improvements to the LNUM patch?
- From: Ralph Hempel <rhempel@...>
- Date: Mon, 14 Apr 2008 15:53:55 -0400
Aladdin Lampé wrote:
I would like to use Lua in a "financial" context, where using
"doubles" for floating point decimal numbers is not enough regarding
to precision. Indeed, dealing with large monetary values may trigger
overflows in the calculations... I certainly do not want this to
<long winded response>
In my pbLua application, I had the opposite problem. I had compiled
Lua to be strictly 32 bit integers and had a strange hybrid mix
of single precision float and integers that occasionally gave
strange results if the programmer was not careful.
In the end, I made a userdata library that implemented float as
its own data type and then added a metatable with the built-in
operations for +-/* , the comparisons, as well as a tostring()
and concat() capability.
It was not that hard and once again made me appreciate the care
and thought that has gone into making the Lua C API a thing
of frightening simplicity and beauty.
</long winded response>
I would suggest having a look at creating your own userata for
high precision monetary values, and implementing a metatable
with overrides for the basic Lua operations.
You may also end up having to add functions to create instances
of the type etc. See the C API and userdata secions in the Blue PiL