Re: Formatting numbers without precision loss

[Lorenzo Donati <lorenzodonatibz@...>]

On 20/06/2023 16:14, Hugo Musso Gualandi wrote:
> In Pallene we try from "%.6g" to "%.17g" and pick the smallest one that 
> round-trips to the original number. (We can't use %a because our output 
> is C, not Lua). 

Are you bound to C89? C99 has %a:

https://en.cppreference.com/w/c/io/fprintf

Note in the table down that page where %a is mentioned:

"The default precision is sufficient for exact representation of the value."

Moreover "strtod" support that syntax (BTW, it also supports infinities 
and NaNs):

https://en.cppreference.com/w/c/string/byte/strtof

so you can have perfect round-trip conversion.



-- Lorenzo