I need to compute the absolute value of the minimum signed int value
for each signed integral type. This value isn't representable as a
signed int, but it is representable as an unsigned int.

This is easy when a larger signed type is available:

int32_t min_int32 = std::numeric_limits<int32_t>::min();
int64_t abs_min_int32= -int64_t(min_int32);
uint32_t answer = uint32_t(abs_min_int32);

I couldn't come up with an elegant solution when attempting this for
the 64-bit type. With a two's complement representation, it just so
happens that reinterpreting the min signed int as an unsigned value
produces the correct result:

int64_t min_int64 = std::numeric_limits<int64_t>::min();
uint64_t answer = uint64_t(min_int64);

but this felt rather inelegant. Can anyone think of a more elegant
solution that does not assume a two's complement binary
representation?

I should note that the standard does not seem to require that
abs(min_int) is representable as a uint for a given size, so let's
limit our consideration to platforms where it is representable.

Regards,
Jeremy

Uli

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