Question

$5.7 –

“[..]For addition, either both operands shall have arithmetic or enumeration type, or one operand shall be a pointer to a completely defined object type and the other shall have integral or enumeration type.

2 For subtraction, one of the following shall hold:
— both operands have arithmetic or enumeration type; or
— both operands are pointers to cv-qualified or cv-unqualified versions of the same completely defined object type; or
— the left operand is a pointer to a completely defined object type and the right operand has integral or enumeration type.

int main(){
        int buf[10];
        int *p1 = &buf[0];
        int *p2 = 0;

        p1 + p2;       // Error

        p1 - p2;       // OK
}

So, my question is why ‘pointer addition’ is not supported in C++ but ‘pointer subtraction’ is?

Answer 1

The difference between two pointers means the number of elements of the type that would fit between the targets of the two pointers. The sum of two pointers means…er…nothing, which is why it isn’t supported.