 <p>In the C++ code you are translating to C#, look for a macro definition or inline function definition for <code>SIGN</code>. The definition should spell out exactly how you should implement it in C#.</p> <p>If I had to guess from the name, <code>SIGN(x,y)</code> returns true if <code>x</code> and <code>y</code> have the same sign, and false otherwise.</p>