writeln double precision

[Arun Chandrasekaran]

On Monday, 23 October 2017 at 14:07:06 UTC, Arun Chandrasekaran 
wrote:
> I've written a simple tool [1] to find the DET and CMC 
> specifically for biometrics performance measurement.
>
> When I generate the report, I expected to see high precision 
> floating point numbers, but I see that writefln trims the 
> precision to the last 6 digits after decimal point.
>
> Am I doing the right thing here? Should I use a different 
> format specifier?
>
> [1] https://bitbucket.org/carun/biometrics-reports/src
>
> Cheers,
> Arun

```
void main() {
     double a = 22/7.0;
     import std.stdio: writeln, writefln;
     writefln("%.51f", a);
}
```

and it prints all the decimals. So I'm happy that I have not lost 
the precision. But why does the compiler bring the C baggage for 
the integer division? Why do I need to `cast (double)` ? Can't 
the compiler figure it out?