On Saturday, 6 November 2021 at 13:27:55 UTC, kdevel wrote:
On Thursday, 4 November 2021 at 00:53:11 UTC, jfondren wrote:
On Wednesday, 3 November 2021 at 20:36:08 UTC, russhy wrote:
Keeping things simple helps debugging!
I'd still have to run your program to be sure of its simple
logic, though. The real star d feature that would help with
debugging is unittest:
What about the number 0 (zero)?
Not treating it as positive is a bug that I introduced in a
rewrite.
If 0 is considered to be excluded from the domain how would one
define in D a type which cannot represent 0 in the first place?
Follow-up question: Are there language facilities such that one
could initialize an array of these non-zero-ints like?:
```
nzint [] numbers = [ -2, -1, 1, 2 ];
```
In general, you use a constructor that tests for non-zero and you
take care to maintain the invariant. D has some tools (like
invariant) to help with that, but it's not a dependent-typed
language.
For this specific example, you can sort of do that with
std.typecons.Nullable
```d
unittest {
import std.typecons : Nullable, nullable;
import std.algorithm : map;
import std.array : array;
alias NonZero(T) = Nullable!(T, 0);
NonZero!int[] numbers = [-2, -1, 0, 1, 2].map!(i =>
NonZero!int(i)).array;
int sum;
int invalids;
foreach (n; numbers) {
if (n.isNull) invalids++;
else sum += n.get;
}
assert(sum == 0);
assert(invalids == 1);
}
```
