fix geometry::get return type (#39)

Change-Id: I0dc4d61a67849a28fda34bde45a25784031f6b37

geometry/src/get.hpp

@@ -6,17 +6,34 @@
 #include <utility>
 
 namespace geometry {
+namespace detail {
+
+template <class T>
+auto get() -> void = delete;
+
+template <class B>
+struct get_fn
+{
+  template <
+      class V,
+      class = std::enable_if_t<
+          algebra_type_t<std::decay_t<V>>::template is_multivector_v<
+              std::decay_t<V>> and
+          std::decay_t<V>::template contains<B>>>
+  constexpr decltype(auto) operator()(V && v) const
+  {
+    return get<B>(std::forward<V>(v));
+  }
+};
+
+}  // namespace detail
+
+inline namespace cpo {
 
 /// access a blade of a multivector
 ///
-template <
-    class B,
-    class V,
-    class = std::enable_if_t<algebra_type_t<
-        std::decay_t<V>>::template is_multivector_v<std::decay_t<V>>>>
-constexpr auto get(V&& v)
-{
-  return get<B>(std::forward<V>(v));
-}
+template <class B>
+inline constexpr auto get = detail::get_fn<B>{};
 
+}  // namespace cpo
 }  // namespace geometry

test/BUILD.bazel

@@ -26,6 +26,16 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "algebra_get_test",
+    size = "small",
+    srcs = ["algebra_get_test.cpp"],
+    deps = [
+        "//:geometry",
+        "@skytest",
+    ],
+)
+
 cc_test(
     name = "algebra_pruned_expressions_test",
     size = "small",

test/algebra_get_test.cpp

@@ -0,0 +1,127 @@
+#include "geometry/geometry.hpp"
+#include "skytest/skytest.hpp"
+
+#include <utility>
+
+template <std::size_t... Is>
+constexpr auto e = ::geometry::algebra<double, 2>::e<Is...>;
+
+template <std::size_t... Is>
+using blade = typename ::geometry::algebra<double, 2>::template blade<Is...>;
+
+auto main() -> int
+{
+  using namespace ::skytest::literals;
+  using ::skytest::eq;
+  using ::skytest::expect;
+
+  "get lvalue ref"_ctest = [] {
+    auto x = e<> + e<0>;
+
+    using ::geometry::get;
+
+    static_assert(std::is_same_v<blade<>&, decltype(get<blade<>>(x))>);
+    static_assert(
+        std::is_same_v<blade<>&, decltype(::geometry::get<blade<>>(x))>);
+
+    static_assert(std::is_same_v<blade<0>&, decltype(get<blade<0>>(x))>);
+    static_assert(
+        std::is_same_v<blade<0>&, decltype(::geometry::get<blade<0>>(x))>);
+
+    return expect(true);
+  };
+
+  "get const lvalue ref"_ctest = [] {
+    const auto x = e<> + e<0>;
+
+    using ::geometry::get;
+
+    static_assert(std::is_same_v<const blade<>&, decltype(get<blade<>>(x))>);
+    static_assert(
+        std::is_same_v<const blade<>&, decltype(::geometry::get<blade<>>(x))>);
+
+    static_assert(std::is_same_v<const blade<0>&, decltype(get<blade<0>>(x))>);
+    static_assert(
+        std::
+            is_same_v<const blade<0>&, decltype(::geometry::get<blade<0>>(x))>);
+
+    return expect(true);
+  };
+
+  "get rvalue ref"_ctest = [] {
+    auto x = e<> + e<0>;
+
+    using ::geometry::get;
+
+    static_assert(
+        std::is_same_v<blade<>&&, decltype(get<blade<>>(std::move(x)))>);
+    static_assert(
+        std::is_same_v<
+            blade<>&&,
+            decltype(::geometry::get<blade<>>(std::move(x)))>);
+
+    static_assert(
+        std::is_same_v<blade<0>&&, decltype(get<blade<0>>(std::move(x)))>);
+    static_assert(
+        std::is_same_v<
+            blade<0>&&,
+            decltype(::geometry::get<blade<0>>(std::move(x)))>);
+
+    return expect(true);
+  };
+
+  "get const rvalue ref"_ctest = [] {
+    const auto x = e<> + e<0>;
+
+    using ::geometry::get;
+
+    // NOLINTBEGIN(performance-move-const-arg)
+
+    static_assert(
+        std::is_same_v<const blade<>&&, decltype(get<blade<>>(std::move(x)))>);
+    static_assert(
+        std::is_same_v<
+            const blade<>&&,
+            decltype(::geometry::get<blade<>>(std::move(x)))>);
+
+    static_assert(
+        std::
+            is_same_v<const blade<0>&&, decltype(get<blade<0>>(std::move(x)))>);
+    static_assert(
+        std::is_same_v<
+            const blade<0>&&,
+            decltype(::geometry::get<blade<0>>(std::move(x)))>);
+
+    // NOLINTEND(performance-move-const-arg)
+
+    return expect(true);
+  };
+
+  "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(not std::is_invocable_v<decltype(f), decltype(b)>);
+    static_assert(
+        not std::
+            is_invocable_v<decltype(::geometry::get<blade<1>>), decltype(b)>);
+
+    return expect(true);
+  };
+
+  "blade not in multivector"_ctest = [] {
+    const auto x = e<> + e<0>;
+
+    using ::geometry::get;
+    auto f = [](auto x) -> decltype(get<blade<1>>(x)) {};
+
+    static_assert(not std::is_invocable_v<decltype(f), decltype(x)>);
+    static_assert(
+        not std::
+            is_invocable_v<decltype(::geometry::get<blade<1>>), decltype(x)>);
+
+    return expect(true);
+  };
+}