D版のコード

gistfile1.d

module main;

import std.stdio;

struct VECTOR
{
	float x, y, z;
}
VECTOR VSet( float x, float y, float z )
{
	VECTOR rtn;
	rtn.x = x;
	rtn.y = y;
	rtn.z = z;
	return rtn;
}
VECTOR VAdd( const ref VECTOR in_val )
//VECTOR VAdd( VECTOR in_val )
{
	VECTOR rtn;
	rtn.x = in_val.x + 1.0f;
	return rtn;
}

int main(string[] argv)
{
	VECTOR vec = VAdd( VSet( 0.0f, 1.0f, 0.0f) );
	printf( "vec(%f,%f,%f)", vec.x, vec.y, vec.z );
	return 0;
}

/**
エラーメッセージは
main.d(27): Error: function main.VAdd (ref const(VECTOR) in_val) is not callable using argument types (VECTOR)
main.d(27): Error: VSet(0F,1F,0F) is not an lvalue
*/