lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

On Dec 01, 2004, at 14:54, Luiz Henrique de Figueiredo wrote:

One issue I've had from time to time is that the default
   #define LUA_NUMBER_FMT        "%.14g"
is not long enough to do reversible conversions on doubles. I believe
you need %.19g for the conversion to be reversible.

I think it's %.17g for IEEE doubles. (Despite what DBL_DIG says!)
Lua was like that once, but then you get ugly things like this:




Users complaint that this is an error in Lua! And it does not help to point
them to docs like ...

Can you imagine a document that it would be helpful to point your users at? If you can, then perhaps we can write it.

As I see it Lua used to do The Right Thing. It used to use %.17g which would give reliable external and internal conversion. As long as the C library was "good enough". glibc and FreeBSD libc were good enough, but many others weren't. It's a shame that Lua now masks poor quality C implementations at the expense of reliability. It's not particularly a shame that you changed it, it's a shame that the state of C libraries meant you felt compelled to change it.

David Jones