How can I resolve ' [C3312] no callable 'get' function found for type 'FVector' ' when I try to use C++ Structured Binding for FVectorxd

Development Programming & Scripting
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1

I want to try the use of structured binding(tuple-like by add std::tuple_size and std::tuple_element) in C++ for “FVectorxd”, but I keep encountering errors when trying.

However, when I tried to replicate it simply on the “Compiler Explorer” website, the compilation was successful . So I’m not sure where the issue lies.

image-20230419010004508
image-202304190100045081801×282 55.1 KB

Intellisense does not show error prompts.

image-20230419014410456

#pragma once
#include <utility>
#include <type_traits>
#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "Tools.generated.h"
​
// mathch vectorxd concepts
template<typename T>
concept contain_freal_type = requires
{
typename T::FReal;
};
​
template<typename Vector>
concept vector_2d_type = contain_freal_type<Vector> && requires
{
Vector::X;
Vector::Y;
Vector::XY;
};
​
template<typename Vector>
concept vector_3d_type = contain_freal_type<Vector> && requires
{
Vector::X;
Vector::Y;
Vector::Z;
Vector::XYZ;
};
template<typename Vector>
concept vector_4d_type = contain_freal_type<Vector> && requires
{
Vector::X;
Vector::Y;
Vector::Z;
Vector::W;
Vector::XYZW;
};
template<typename Vector>
concept vector_type = vector_2d_type<Vector> || vector_3d_type<Vector>
|| vector_4d_type<Vector>;
// add std::tuple_size and std::tuple_element
namespace std
{
template<::vector_type Vector2D>
struct tuple_size<Vector2D> : std::integral_constant<size_t, 2>
{};

template<::vector_3d_type Vector3D>
struct tuple_size<Vector3D> : std::integral_constant<size_t, 3>
{};

template<::vector_4d_type Vector4D>
struct tuple_size<Vector4D> : std::integral_constant<size_t, 4>
{};

template<::vector_type Vector, size_t Index>
struct tuple_element<Index, Vector>
{
using type = typename Vector::FReal;
};
​
​
} // end namespace std
​
template<size_t Index>
constexpr auto Get(::vector_type auto const &Vec)
{
if constexpr (Index == 0) return Vec.X;
if constexpr (Index == 1) return Vec.Y;
if constexpr (Index == 2) return Vec.Z;
if constexpr (Index == 3) return Vec.W;
}
​
template<size_t Index>
auto get(::vector_type auto &Vec)
{
return Get<Index>(Vec);
}
​
template<size_t Index>
auto get(::vector_type auto const &Vec)
{
return Get<Index>(Vec);
}
template<size_t Index>
auto get(::vector_type auto &&Vec)
{
return Get<Index>(Vec);
}
​
template<size_t Index>
auto get(::vector_type auto const &&Vec)
{
return Get<Index>(Vec);
}
UCLASS()
class DEMO_API UTools : public UBlueprintFunctionLibrary
{
GENERATED_BODY()
public:
// simply test
static void Test()
{
auto[X, Y, Z] = FVector(1., 2., 3.0);
}
};
​

I am using the “MSVC-14.34.31933” compilation environment with the C++ standard set to “CppStandardVersion.Latest”.

IDE: Rider;

Thank OGs!

2

The FVector class is from the UE::Math namespace:

using FVector = UE::Math::TVector<double>;

The compiler is looking for the ‘get’ functions in the same namespace, so if you move the get functions into that namespace it will fix the problem:

namespace UE::Math
{

	template<size_t Index>
	auto get(::vector_type auto& Vec)
	{
		return Get<Index>(Vec);
	}

	template<size_t Index>
	auto get(::vector_type auto const& Vec)
	{
		return Get<Index>(Vec);
	}

       ... 
}
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3

Thank you for your help!