Support 0-dimensional vectors

libs/geom/include/psemek/geom/vector.hpp

@@ -3,11 +3,33 @@
 #include <cstddef>
 #include <utility>
 #include <type_traits>
+#include <stdexcept>
 #include <cmath>
 
 namespace psemek::geom
 {
 
+	namespace detail
+	{
+
+		template <typename T, std::size_t N>
+		struct empty_array_helper
+		{
+			using type = T[N];
+		};
+
+		template <typename T>
+		struct empty_array_helper<T, 0>
+		{
+			struct type
+			{
+				T const & operator[](std::size_t) const { throw std::runtime_error("Attempt to index a zero vector"); }
+				T & operator[](std::size_t) { throw std::runtime_error("Attempt to index a zero vector"); }
+			};
+		};
+
+	}
+
 	template <typename T, std::size_t N>
 	struct vector
 	{
@@ -15,7 +37,7 @@ namespace psemek::geom
 
 		using scalar_type = T;
 
-		T coords[N];
+		detail::empty_array_helper<T, N>::type coords;
 
 		vector() = default;
 		vector(vector const &) = default;
@@ -295,6 +317,15 @@ namespace psemek::geom
 		return ort(v0, v1);
 	}
 
+	template <typename T, std::size_t N>
+	vector<T, N> pointwise_mult(vector<T, N> const & v0, vector<T, N> const & v1)
+	{
+		vector<T, N> result;
+		for (std::size_t i = 0; i < N; ++i)
+			result[i] = v0[i] * v1[i];
+		return result;
+	}
+
 	template <typename T, std::size_t N>
 	vector<T, N> lerp(vector<T, N> const & v0, vector<T, N> const & v1, T const & t)
 	{
@@ -327,6 +358,12 @@ namespace psemek::geom
 	template <typename Stream, typename T, std::size_t N>
 	Stream & operator << (Stream & os, vector<T, N> const & v)
 	{
+		if constexpr (N == 0)
+		{
+			os << "()";
+			return os;
+		}
+
 		os << '(' << v[0];
 		for (std::size_t i = 1; i < N; ++i)
 			os << ", " << v[i];