Need access to `boolN`'s `?:` operator

[rickbrew]

According to https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-operators#boolean-math-operators , boolN and boolMxN should support the ?: operator as a per-component selector.

AFAIK, you can't overload the ?: operator in C#/.NET, at least not in the way we'd need for this, and I'd be surprised if that changes.

So I'm proposing to surface this as a method, Hlsl.Select():

public static class Hlsl
{
    public static float Select(bool selector, float value1, float value2);
    public static float2 Select(bool2 selector, float2 value1, float2 value2);
    public static float3 Select(bool3 selector, float3 value1, float3 value2);
    public static float4 Select(bool4 selector, float4 value1, float4 value2);
    ...
    public static float1x4 Select(bool1x4 selector, float1x4 value1, float1x4 value2);
    public static float2x4 Select(bool2x4 selector, float2x4 value1, float2x4 value2);
    public static float3x4 Select(bool3x4 selector, float3x4 value1, float3x4 value2);
    public static float4x4 Select(bool4x4 selector, float4x4 value1, float4x4 value2);
    ...
    // All other valid combinations of types and vector/matrix sizes
}

Access to this would allow me to change this:

float4 value1 = ...;
float4 value2 = ...;
bool4 selector = ...;
uint4 mask = ~(Hlsl.BoolToUInt(selector) - 1);
float4 result = Hlsl.AsFloat((mask & Hlsl.AsUInt(value1)) | (~mask & Hlsl.AsUInt(value2)));

to just:

float4 value1 = ...;
float4 value2 = ...;
bool4 selector = ...;
float4 result = Hlsl.Select(selector, value1, value2);

This would be a good win for legibility, and maybe performance.