Handling big FP numbers

[Murilo]

On Saturday, 9 February 2019 at 04:30:22 UTC, DanielG wrote:
> On Saturday, 9 February 2019 at 03:33:13 UTC, Murilo wrote:
>> Thanks but here is the situation, I use printf("%.20f", 0.1); 
>> in both C and D, C returns 0.10000000000000000555 whereas D 
>> returns 0.10000000000000001000. So I understand your point, D 
>> rounds off more, but that causes loss of precision, isn't that 
>> something bad if you are working with math and physics for 
>> example?
>
> 0.1 in floating point is actually 0.100000001490116119384765625 
> behind the scenes.
>
> So why is it important that it displays as:
>
> 0.10000000000000000555
>
> versus
>
> 0.10000000000000001000
>
> ?
>
> *Technically* the D version has less error, relative to the 
> internal binary representation. Since there's no exact way of 
> representing 0.1 in floating point, the computer has no way of 
> knowing you really mean "0.1 decimal". If the accuracy is that 
> important to you, you'll probably have to look into 
> software-only number representations, for arbitrary decimal 
> precision (I've not explored them in D, but other languages 
> have things like "BigDecimal" data types)

Thank you very much for clearing this up. But how do I make D 
behave just like C? Is there a way to do that?