left operand
right operand
set if an overflow occurs, is not affected otherwise
the sum
for (uint i = 0; i < 10; ++i) { bool overflow; immutable uint r = addu (uint.max - i, uint.max - i, overflow); assert (r == 2 * (uint.max - i)); assert (overflow); } bool overflow; assert(addu(2, 3, overflow) == 5); assert(!overflow); assert(addu(1, uint.max - 1, overflow) == uint.max); assert(!overflow); assert(addu(uint.min, -1, overflow) == uint.max); assert(!overflow); assert(addu(uint.max, 1, overflow) == uint.min); assert(overflow); overflow = false; assert(addu(uint.min + 1, -1, overflow) == uint.min); assert(overflow); assert(addu(0, 0, overflow) == 0); assert(overflow); // sticky
bool overflow; assert(addu(2L, 3L, overflow) == 5); assert(!overflow); assert(addu(1, ulong.max - 1, overflow) == ulong.max); assert(!overflow); assert(addu(ulong.min, -1L, overflow) == ulong.max); assert(!overflow); assert(addu(ulong.max, 1, overflow) == ulong.min); assert(overflow); overflow = false; assert(addu(ulong.min + 1, -1L, overflow) == ulong.min); assert(overflow); assert(addu(0L, 0L, overflow) == 0); assert(overflow); // sticky
Add two unsigned integers, checking for overflow (aka carry).
The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.