Should (p - q) be disallowed in @safe code?

[Paul Backus]

On Thursday, 1 January 2026 at 17:20:33 UTC, Walter Bright wrote:
> On 1/1/2026 7:16 AM, claptrap wrote:
>> I use this all the time to iterate multiple arrays in lockstep.
>> 
>> size_t offset = q-p;
>> 
>> you access q with "p[offset]", and you just iterate p
>> 
>> I tried to avoid using it but it is just faster sometimes,
>
> @safe code doesn't allow pointer arithmetic, and so such code 
> would have to be marked @trusted anyway.

Pointer *subtraction* is allowed in @safe code because the result 
is an integer, and all integers are [safe values][1].

For example, this compiles using the latest release of DMD:

```d
import std.stdio;

void main() @safe
{
     int* p = new int, q = new int;
     writeln(q - p);
}
```

[1]: https://dlang.org/spec/function.html#safe-values