What's the easiest way to print a double in maximum precision?

On Wednesday, 18 January 2017 at 00:09:42 UTC, Nordlöw wrote:
> What's the easiest way to print a double in maximum precision?

https://github.com/pineapplemachine/mach.d/blob/master/mach/text/numeric/floats.d#L60

You can also try the formatting directive "%.20f" but unlike the former I can't offer any guarantees of its accuracy (it's probably accurate)

On Wednesday, 18 January 2017 at 00:23:37 UTC, pineapple wrote:
> On Wednesday, 18 January 2017 at 00:09:42 UTC, Nordlöw wrote:
>> What's the easiest way to print a double in maximum precision?
>
> https://github.com/pineapplemachine/mach.d/blob/master/mach/text/numeric/floats.d#L60
>
> You can also try the formatting directive "%.20f" but unlike the former I can't offer any guarantees of its accuracy (it's probably accurate)

Alternatively use %a to print in hex to verify exact bit patterns.

On Wednesday, 18 January 2017 at 00:09:42 UTC, Nordlöw wrote:
> What's the easiest way to print a double in maximum precision?

%.6g for floats and %.17g for doubles. This is for example what's used on std.json to get a perfect conversion from string to value. the number is the maximum number of digits in the fractional part.

6 and 17 are rounded, real values can be found  here (https://en.wikipedia.org/wiki/Floating_point#Internal_representation)

see also:

http://stackoverflow.com/questions/16839658/printf-width-specifier-to-maintain-precision-of-floating-point-value/21162120#21162120

and this

https://github.com/dlang/phobos/pull/4343#issuecomment-220810593

On Wednesday, 18 January 2017 at 03:36:39 UTC, Nicholas Wilson wrote:
> Alternatively use %a to print in hex to verify exact bit patterns.

+1, if it doesn't have to be human-readable.