How to detect overflow

[Namal via Digitalmars-d-learn]

On Wednesday, 4 November 2015 at 07:59:44 UTC, Ali Çehreli wrote:
> On 11/03/2015 11:52 PM, Namal wrote:
>
>>> http://dlang.org/phobos/core_checkedint.html
>>
>> It says:
>>
>>
>> "The overflow is sticky, meaning a sequence of operations can 
>> be done
>> and overflow need only be checked at the end."
>>
>> But how can I make multiple operations? I can only put 2 
>> values in the
>> function.
>
> import core.checkedint;
>
> void main() {
>     bool overflowed;
>     auto result = adds(int.max, 1, overflowed); // this 
> overflows
>     adds(1, 2, overflowed);     // this does not reset the flag
>
>     assert(overflowed);
> }
>
> Ali

wow, this I don't understand at all, how do those two operations 
connected to each other? By the bool value?