double vs real

[bearophile]

Shriramana Sharma:

> Hello. I like that D exposes to me the real type to maximally 
> utilize
> the machine's numerical precision. Since I am writing a program
> (currently in C++ but I am thinking of moving to D) that has to 
> handle
> lots of fractional numbers (calculating offset curves and such) 
> I am
> wondering whether/when I should real instead of double or even 
> any
> arguments in favour of staying with double (compatibility with
> C/C++?). Any pointers appreciated please? I checked the FAQ but 
> it
> doesn't seem to mention this.

If you have to store many reals, they require more memory than 
doubles (how much is relative to the operating system). Regarding 
speed in theory double and real should give the same, but in 
practice theory and practice often differ. As suggested, use an 
alias like:

alias FP = real;

And switch from double and real, and take a look at the 
differences. But don't perform such switch at the end, do it now 
and then to be sure everything keeps working correctly.

Bye,
barophile