On Saturday, 9 February 2019 at 05:46:22 UTC, H. S. Teoh wrote:
On Sat, Feb 09, 2019 at 03:52:38AM +0000, Murilo via
Digitalmars-d-learn wrote:
On Saturday, 9 February 2019 at 03:28:24 UTC, Adam D. Ruppe
wrote:
[...]
> But you can change this with the format specifiers (use
> `writefln` instead of `writeln` and give a precision
> argument) or, of course, you can use the same C printf
> function from D.
Thanks, but which precision specifier should I use? I already
tried "%.20f" but it still produces a result different from C?
Is there a way to make it identical to C?
I say again, you're asking for far more digits than are
actually there. The extra digits are only an illusion of
accuracy; they are essentially garbage values that have no real
meaning. It really does not make any sense to print more digits
than are actually there.
On the other hand, if your purpose is to export the double in a
textual representation that guarantees reproduction of exactly
the same bits when imported later, you could use the %a format
which writes out the mantissa in exact hexadecimal form. It can
then be parsed again later to reproduce the same bits as was in
the original double.
Or if your goal is simply to replicate C behaviour, there's
also the option of calling the C fprintf directly. Just import
core.stdc.stdio or declare the prototype yourself in an
extern(C) declaration.
T
Thanks, but even using core.stdc.stdio.fprintf() it still shows a
different result on the screen. It seems this is a feature of D I
will have to get used to and accept the fact I can't always get
the same number as in C even though in the end it doesn't make a
difference cause as you explained the final digits are just
garbage anyway.
