remove invalid get overload for blade types (#58)

`get` should not be invocable for `blade` types. The ratio function of
exercise 2.12.1 is updated to obtain the `coefficient` of each `blade`
parameter.

This commit partially reverts 8b5b03b.

Change-Id: Ibe893d2a7a6ccc692a21522fa1f27e055023b042

exercises/2.12.1.cpp

@@ -17,16 +17,14 @@ constexpr auto e1 = e<1>;
 constexpr auto e2 = e<2>;
 constexpr auto e3 = e<3>;
 
-template <class B1, class B2>
+template <class B>
 [[nodiscard]]
-constexpr auto ratio(B1 b1, B2 b2)
+constexpr auto ratio(B b1, B b2)
 {
-  static_assert(::geometry::is_blade_v<B2>);
+  static_assert(::geometry::is_blade_v<B>);
 
-  const auto a1 = ::geometry::get<B2>(b1);
-  const auto a2 = ::geometry::get<B2>(b2);
-
-  assert(b1 == ((a1 / a2) * b2));
+  const auto a1 = b1.coefficient;
+  const auto a2 = b2.coefficient;
 
   return a1 / a2;
 }

geometry/src/get.hpp

@@ -19,20 +19,11 @@ struct get_fn
   template <
       class V,
       class D = std::decay_t<V>,
-      std::enable_if_t<is_multivector_v<D> and D::template contains<B>, bool> =
-          true>
+      class = std::enable_if_t<is_multivector_v<D> and D::template contains<B>>>
   constexpr decltype(auto) operator()(V && v) const
   {
     return get<B>(std::forward<V>(v));
   }
-  template <
-      class V,
-      class D = std::decay_t<V>,
-      std::enable_if_t<is_blade_v<D> and std::is_same_v<B, D>, bool> = true>
-  constexpr decltype(auto) operator()(V && v) const
-  {
-    return std::forward<V>(v).coefficient;
-  }
 };
 
 }  // namespace detail

test/algebra_get_test.cpp

@@ -97,25 +97,12 @@ auto main() -> int
     return expect(true);
   };
 
-  "get used with blade"_ctest = [] {
+  "get not used with multivector"_ctest = [] {
     const auto b = e<1>;
 
     using geometry::get;
     auto f = [](auto x) -> decltype(get<blade<1>>(x)) {};
 
-    static_assert(std::is_invocable_v<decltype(f), decltype(b)>);
-    static_assert(
-        std::is_invocable_v<decltype(::geometry::get<blade<1>>), decltype(b)>);
-
-    return expect(true);
-  };
-
-  "get used with wrong blade"_ctest = [] {
-    const auto b = e<2>;
-
-    using geometry::get;
-    auto f = [](auto x) -> decltype(get<blade<1>>(x)) {};
-
     static_assert(not std::is_invocable_v<decltype(f), decltype(b)>);
     static_assert(
         not std::