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kenpusney/fizzbuzz.cpp

Created April 25, 2019 05:33
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fizzbuzz.cpp
#include <string>
using namespace std;
constexpr char to_char(unsigned x)
{
return x % 10 + '0';
}
template <unsigned... digits>
constexpr char to_chars[] = {to_char(digits)..., '\0'};
template <unsigned rem, unsigned... digits>
constexpr string_view explode = explode<rem / 10, rem % 10, digits...>;
template <unsigned... digits>
constexpr string_view explode<0, digits...> = {to_chars<digits...>};
template <unsigned num>
constexpr string_view string_of = explode<num>;
constexpr bool can_divide(unsigned x, unsigned y)
{
return x % y == 0;
}
constexpr bool contains(string_view x, char m)
{
return x.find(m) != x.npos;
}
template <unsigned x, unsigned y>
constexpr bool can_divide_or_contains = can_divide(x, y) || contains(string_of<x>, to_char(y));
template <unsigned x, bool for3, bool for5>
constexpr string_view fizzbuzz_of_impl = string_of<x>;
template <unsigned x>
constexpr string_view fizzbuzz_of_impl<x, true, false> = "Fizz";
template <unsigned x>
constexpr string_view fizzbuzz_of_impl<x, false, true> = "Buzz";
template <unsigned x>
constexpr string_view fizzbuzz_of_impl<x, true, true> = "FizzBuzz";
template <unsigned x>
constexpr string_view fizzbuzz_of =
fizzbuzz_of_impl<x, can_divide_or_contains<x, 3>, can_divide_or_contains<x, 5>>;
int main()
{
static_assert(fizzbuzz_of<1> == "1");
static_assert(fizzbuzz_of<3> == "Fizz");
static_assert(fizzbuzz_of<5> == "Buzz");
static_assert(fizzbuzz_of<15> == "FizzBuzz");
static_assert(fizzbuzz_of<2> == "2");
static_assert(fizzbuzz_of<51> == "FizzBuzz");
}
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