On Wednesday, 9 October 2019 at 05:46:12 UTC, berni44 wrote:
On Tuesday, 8 October 2019 at 20:37:03 UTC, dan wrote:
But i would like to be able to do this without knowing the
expansion of pi, or writing too much code, especially if
there's some d function like writeAllDigits or something
similar.
You can use the property .dig to get the number of significant
digits of a number:
writeln(PI.dig); // => 18
You still need to account for the numbers before the dot. If
you're happy with scientific notation you can do:
auto t = format("%.*e", PI.dig, PI);
writeln("PI = ",t);
Using the '.dig' property is a really nice idea and looks very
useful for this. A clarification though - It's the significant
digits in the data type, not the value. (PI is 18 because it's a
real, not a double.) So:
writeln(1.0f.dig, ", ", float.dig); => 6, 6
writeln(1.0.dig, ", ", double.dig); => 15, 15
writeln(1.0L.dig, ", ", real.dig); => 18, 18
Another possibility would be to combine the '.dig' property with
the "%g" option, similar to the use "%e" shown. For example,
these lines:
writeln(format("%0.*g", PI.dig, PI));
writeln(format("%0.*g", double.dig, 1.0));
writeln(format("%0.*g", double.dig, 100.0));
writeln(format("%0.*g", double.dig, 1.00000001));
writeln(format("%0.*g", double.dig, 0.00000001));
produce:
3.14159265358979324
1
100
1.00000001
1e-08
Hopefully experimenting with the different formatting options
available will yield one that works for your use case.
