Compile-time integer arithmetic without using templates

[Juha Nieminen]

I think the new 'constexpr' keyword is actually quite cool. For example
this calculates the integral square root of an integer, rounded up, at
compile time.

//------------------------------------------------------------------------
#include <cstdint>

constexpr std::uint64_t isqrtIter(std::uint64_t value,
std::uint64_t low,
std::uint64_t high)
{
return (low < high ? (((low+high)/2) * ((low+high)/2) < value ?
isqrtIter(value, (low+high)/2 + 1, high) :
isqrtIter(value, low, (low+high)/2))
: low);
}

constexpr std::uint64_t isqrt(std::uint64_t value)
{
return isqrtIter(value, 1, UINT32_MAX);
}
//------------------------------------------------------------------------

This can actually have practical use, for example to create static arrays
that have the size of sqrt(constant), which might be useful for some
algorithms.