Help with Tamamo 's freeform door script

[Asuna Yuuki Nagato]

It doesn't work for me anyway:

[INFO] External ZScript Parser

[Info] Compiling the editor script buffer...
[Info] Pass 1: Parsing
[Info] Pass 2: Preprocessing
[Info] Pass 3: Registration
[Info] Pass 4: Analyzing Code
[Error] ZQ_BUFFER Line 56 @ Columns 9-25 - Error T021: Function OppositeDir(int) has not been declared.
[Info] Failure!