quotientRemainder.cpp

#define NO_SCALAR_REFERENCES_USED_IN_PATTERNS 1

#include "matchit.h"
#include <iostream>

constexpr auto qr = [](auto divisor)
{
  using namespace matchit;
  return [divisor](auto quotient, auto remainder)
  {
    return and_(app(_ / divisor, quotient), app(_ % divisor, remainder));
  };
};

constexpr std::array<int32_t, 2> quoRem(int32_t dividend, int32_t divisor)
{
  using namespace matchit;
  Id<int32_t> q;
  Id<int32_t> r;
  return match(dividend)(
      // clang-format off
        pattern | qr(divisor)(q, r) = [&] { return std::array<int32_t, 2>{*q, *r}; },
        pattern | _                 = [&] { return std::array<int32_t, 2>{0, 0}; }
      // clang-format on
  );
}

// todo: make Id variants for Id<T> Id<T&> Id<T const&> Id<T&&>
constexpr auto qrResult1 = quoRem(12, 6);
static_assert(qrResult1[0] == 2);
static_assert(qrResult1[1] == 0);

constexpr auto qrResult2 = quoRem(12, -5);
static_assert(qrResult2[0] == -2);
static_assert(qrResult2[1] == 2);

int32_t main()
{
  auto const result = quoRem(12, 7);
  std::cout << result[0] << "\t" << result[1] << std::endl;
  return 0;
}