Re: Providing implicit conversion of

[Danilo via Digitalmars-d-learn]

On Sunday, 21 January 2024 at 16:05:40 UTC, Gavin Gray wrote:
The following code:
  ulong charlie = 11;
  long johnstone = std.algorithm.comparison.max(0, -charlie);
  writeln(format!"johnstone %s"(johnstone));

Results in (without any warning(s)):
johnstone -11

However you choose to look at it, this means -11 > 0 
(regardless of all arguments concerning implicit conversions, 
1's and 2's complements, being efficient, etc).

The language should not allow unary unsigned anything.

This returns -1:
```d
import std;

void main() {
    ulong charlie = 11;
    long johnstone = std.algorithm.comparison.max(0, -charlie);
    writeln(format!"johnstone %s"(johnstone));
}
```

If you change the result type to `auto johnstone`, it returns 
18446744073709551605:
```d
module app;

import std;

void main() {
    ulong charlie = 11;
    auto johnstone = std.algorithm.comparison.max(0, -charlie);
    writeln(format!"johnstone %s"(johnstone));
}
```

So what happens is, max() correctly returns 18446744073709551605,
but if you explicitely receive a `long`, the `ulong` is converted 
to a long,
resulting in -11.

With `auto johnstone` or `ulong johnstone` the result is correct:
```d
import std;

void main() {
    ulong charlie = 11;
    ulong johnstone = std.algorithm.comparison.max(0, -charlie);
    writeln(format!"johnstone %s"(johnstone));
}
```

If you take a bigger type, like `Int128`, it is also correct:
```d
import std;

void main() {
    ulong charlie = 11;
    Int128 johnstone = std.algorithm.comparison.max(0, -charlie);
    writeln(format!"johnstone %s"(johnstone));
}
```