implementing units::ratio_add and tests

not yet used in src/include/units/bits/dim_consolidate.h
because it breaks and cascades (due to new exponent we think)

src/include/units/bits/dim_consolidate.h

@@ -56,7 +56,7 @@ struct dim_consolidate<exp_list<E1, ERest...>> {
 
 template<BaseDimension Dim, std::intmax_t Num1, std::intmax_t Den1, std::intmax_t Num2, std::intmax_t Den2, typename... ERest>
 struct dim_consolidate<exp_list<exp<Dim, Num1, Den1>, exp<Dim, Num2, Den2>, ERest...>> {
-  // TODO: provide custom implementation for ratio_add
+  // TODO: we have ration_add now, but dim_consolidate etc, now need to cope with our new ratio
   using r1 = std::ratio<Num1, Den1>;
   using r2 = std::ratio<Num2, Den2>;
   using r = std::ratio_add<r1, r2>;

src/include/units/ratio.h

@@ -35,13 +35,11 @@ namespace units {
 namespace detail {
 
 template<typename T>
-[[nodiscard]] constexpr T abs(T v) noexcept
-{
+[[nodiscard]] constexpr T abs(T v) noexcept {
   return v < 0 ? -v : v;
 }
 
-constexpr std::tuple<std::intmax_t, std::intmax_t, std::intmax_t> normalize(std::intmax_t num, std::intmax_t den, std::intmax_t exp)
-{
+constexpr std::tuple<std::intmax_t, std::intmax_t, std::intmax_t> normalize(std::intmax_t num, std::intmax_t den, std::intmax_t exp) {
   std::intmax_t gcd = std::gcd(num, den);
   num = num * (den < 0 ? -1 : 1) / gcd;
   den = detail::abs(den) / gcd;
@@ -81,13 +79,47 @@ namespace detail {
 template<intmax_t Num, intmax_t Den, intmax_t Exp>
 inline constexpr bool is_ratio<ratio<Num, Den, Exp>> = true;
 
-}  // namespace detail
+template<Ratio R1, Ratio R2>
+constexpr std::tuple<std::intmax_t, std::intmax_t, std::intmax_t> ratio_add_detail() {
+  std::intmax_t num1 = R1::num;
+  std::intmax_t num2 = R2::num;
+
+  // align exponents
+  std::intmax_t new_exp = R1::exp;
+  if constexpr (R1::exp > R2::exp) {
+    new_exp = R1::exp;
+    while (new_exp > R2::exp) {
+      num1 *= 10;
+      --new_exp;
+    }
+  } else if constexpr (R1::exp < R2::exp) {
+    new_exp = R2::exp;
+    while (R1::exp < new_exp) {
+      num2 *= 10;
+      --new_exp;
+    }
+  }
+
+  // common denominator
+  std::intmax_t lcm_den = std::lcm(R1::den, R2::den);
+  num1 = num1 * (lcm_den / R1::den);
+  num2 = num2 * (lcm_den / R2::den);
+
+  return std::make_tuple(num1 + num2, lcm_den, new_exp);
+}
+
+
+template<Ratio R1, Ratio R2>
+struct ratio_add_impl {
+  static constexpr auto detail = ratio_add_detail<R1, R2>();
+  using type = ratio<std::get<0>(detail), std::get<1>(detail), std::get<2>(detail)>;
+};
+}// namespace detail
 
 
 // ratio_add
-// TODO implement ratio_add
-// template<Ratio R1, Ratio R2>
-// using ratio_add = detail::ratio_add_impl<R1, R2>::type;
+template<Ratio R1, Ratio R2>
+using ratio_add = detail::ratio_add_impl<R1, R2>::type;
 
 // ratio_subtract
 // TODO implement ratio_subtract

test/unit_test/static/math_test.cpp

@@ -39,4 +39,5 @@ namespace {
   static_assert(std::is_same_v<decltype(sqrt(4km2)), decltype(2km)>);
   static_assert(std::is_same_v<decltype(sqrt(4ft2)), decltype(2ft)>);
 
+
 }  // namespace

test/unit_test/static/ratio_test.cpp

@@ -76,9 +76,22 @@
   static_assert(std::is_same_v<ratio_sqrt<ratio<0>>, ratio<0>>);
   static_assert(std::is_same_v<ratio_sqrt<ratio<1, 4>>, ratio<1, 2>>);
 
-  // // sqrt with exponents: TODO not working yet. Also not sure the non exponent version is accurate.
-  // static_assert(std::is_same_v<ratio_sqrt<ratio<9, 1, 2>>, ratio<3, 1, 1>>);
-  // static_assert(std::is_same_v<ratio_sqrt<ratio<4>>, ratio<2>>);
+  // sqrt with exponents
+  static_assert(std::is_same_v<ratio_sqrt<ratio<9, 1, 2>>, ratio<3, 1, 1>>);
+  static_assert(std::is_same_v<ratio_sqrt<ratio<4>>, ratio<2>>);
+
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<1, 2, 0>, units::ratio<1, 3, 0>>, units::ratio<5, 6, 0>>);
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<1, 2, 1>, units::ratio<1, 3, 1>>, units::ratio<5, 6, 1>>);
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<3, 8, 2>, units::ratio<2, 7, 2>>, units::ratio<37, 56, 2>>);
+
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<3, 8, 2>, units::ratio<2, 7, 1>>, units::ratio<226, 56, 1>>);
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<2, 7, 1>, units::ratio<3, 8, 2>>, units::ratio<226, 56, 1>>);
+
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<3, 8, -2>, units::ratio<2, 7, -1>>, units::ratio<181, 56, -2>>);
+  static_assert(std::is_same_v<units::ratio_add<units::ratio<2, 7, -1>, units::ratio<3, 8, -2>>, units::ratio<181, 56, -2>>);
+
+
+
 
   // common_ratio
   // note use of ::type is required because template params are changed while stamping out template