Issue
I understand why stl indices are unsigned, because you would never have a negative index. But for normal C arrays, the indices are signed. Why is this?
If there is a good reason for C array indices to be signed, why did they decide to make stl indices different?
Solution
Array indexing in C is really just a pointer offset. x[y]
is exactly the same as *(x + y)
. That allows you to do things like this:
int a[3] = { 1, 2, 3 };
int *p = a; /* p points to a[0] */
printf("p[1]=%d\n", p[1]); /* prints 2 */
p += 2; /* p points to a[2] */
printf("p[-1]=%d\n", p[-1]); /* prints 2 */
Which is why negative array indexing is allowed.
Answered By - dbush Answer Checked By - Mary Flores (PHPFixing Volunteer)
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