On 22.02.2018 01:26, Adam D. Ruppe wrote:
On Thursday, 22 February 2018 at 00:13:43 UTC, SrMordred wrote:
string x = "123";
auto c = x.ptr;
writeln(c[-1]); // 1

That's only happening because pointers bypass range checks.

writeln(c[-1..0]); //BOOM Range violation

But with a slice negative indexes are never allowed, even on a pointer.

Actually, it's slightly more complicated than that. E.g. c[-2..-1] does not trigger the range check and will behave as expected. For slices c[l..r] there is a check whether cast(size_t)l<=cast(size_t)r. The range violation happens because -1 is larger than 0 as an unsigned integer.

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