Best search algorithm to find condition within a range

Alain Ketterlin alain at dpt-info.u-strasbg.fr
Thu Apr 9 13:57:48 CEST 2015


Marko Rauhamaa <marko at pacujo.net> writes:

> The basic arithmetic algorithms are independent of the base.

Right.

> For example, here's how you can add two 128-bit integers in C using
> 64-bit digits:
>
>     typedef struct {
>         uint64_t lo, hi;
>     } uint128_t;
>
>     uint128_t add128(uint128_t x, uint128_t y)
>     {
>         uint128_t result = {
>             .lo = x.lo + y.lo,
>             .hi = x.hi + y.hi
>         };
>         if (result.lo < x.lo)
>             result.hi++;
>         return result;
>     }
>
> Works both for signed and unsigned integers.    

(Slightly off-topic, but...)

No, it would not work for signed integers (i.e., with lo and hi of
int64_t type), because overflow is undefined behavior for signed.

-- Alain.



More information about the Python-list mailing list