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- Subject: Re: Possible improvements to the LNUM patch?
- From: "Dirk Feytons" <dirk.feytons@...>
- Date: Tue, 15 Apr 2008 09:41:39 +0200
On Mon, Apr 14, 2008 at 9:53 PM, Ralph Hempel
> <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
> for details.
I recently discovered one disadvantage of such an approach: relational
operators are only possible on operands of the same type. In other
words, you can't compare such a userdata object with a regular number
since it is by definition false. This might or might not be a problem,
depending on your specific needs but it's certainly something to keep