Read relations from an AUT file.
rel[int, str, int] readAUT(str nameAUTFile)
An AUT file contains tuples of ternary relation as lines with the following format:
- each field is separated by a comma
readAUT takes an AUT file and generates a value of type
write an AUT file
void writeAUT(str nameAUTFile, rel[int, str, int] r)