Division - precision

[Ali Çehreli via Digitalmars-d-learn]

On 05/21/2016 02:45 PM, Rygel wrote:
 > Hi there. I'm a beginners, so my questions could be silly.
 >
 >      double x1 = 7.0;
 >      double x2 = 3.0;
 >      writeln(x1 / x2);
 >
 > from this code i get:
 >
 > 2.33333
 >
 > this is ok but how can i get more digits? For example:
 >
 > 2.333333333.....
 >
 > thx :-)

There are two kinds of precision to talk about in this case:

1) The value: You can't do anything about the precision other than 
picking a more precise type. ('real' has more precision than 'double'.)

2) The display: You can display the value more precisely with a format 
specifier like "%.10f" (with 10 digit precision):

import std.stdio;
import std.string;

void main() {
     double x1 = 7.0;
     double x2 = 3.0;

     pragma(msg, format("%s has %s-digit precision",
                        double.stringof, double.dig));

     writeln("Printing with too many digits:");
     writefln("%.30f", x1 / x2);

     static const betterFormatSpec = format("%%.%sf", double.dig);
     writefln("Printing with just the right amount precision:");
     writefln("(The format string used is \"%s\".)", betterFormatSpec);
     writefln(betterFormatSpec, x1 / x2);
}

In any case, watch Don Clugston's DConf 2016 presentation as an 
eye-opener and great entertainment:

   http://www.ustream.tv/recorded/86406491/highlight/699207

Ali