On Monday, 18 April 2022 at 10:26:16 UTC, HuskyNator wrote:
On a sidenote, I'm surprised D did not choose 0 as the default
floating value. Doesn't almost every language do this? I
understand the thinking behind it, but when the type one uses
in a template influences the behavior of the code, that seems
like a pretty big red flag to me. (Any non-floating type
defaults to 0, but using floats/doubles suddenly introduces
NaN, surely I'm not the only one that sees a problem with this
😅) Especially when it's basically a standard 0 is used for
this. Sorry for the rant.
Let me explain the why:
D default initialization is not designed to replace user-defined
initialization, it's rather made to make bugs related to
non-initialized variables stable, e.g not UB.
The easiest way to get that is to think to references and
pointers. A random garbage value pointed by an alloca may work to
some point (e.g access to member), if it's set to `null` right
after the alloca then you have a stable segfault that always
happens at the same time and is easy to debug.
Similarly, for floating point numbers the D designers considered
that `NaN` was the best choice because FP operations will not
wrongly appear valid when starting operations with NaN.
With integral types, this system does not work as well, as `0`
doesn't create bugs as easily as `null` and `NaN`. The confusion
about the real role of default initialization comes from integral
types I believe.
