HLSL #pragma once equivalent?

Question

What's the equivalent to C/C++-like #pragma once in HLSL includes?

I want (as a contrived example):

// ./dependency.hlsl
float x() { return 0; }

// ./shader.hlsl
#include "./dependency.hlsl" // (./ unnecessary; for question readability)
#include "./dependency.hlsl"

to not fail with error X3003: redefinition of 'x'. #pragma once at the top of my file yields a non-error warning X3568: 'once' : unknown pragma ignored and does nothing!

Answer 1

Use C/C++ macro-like include guards. The contrived dependency.hlsl would look as follows:

#ifndef __DEPENDENCY_HLSL__
#define __DEPENDENCY_HLSL__

float x() { return 0; }

#endif // __DEPENDENCY_HLSL__