Retrieve the data associated with a general constraint of type TAN. Calling this method for a general constraint of a different type leads to an exception. You can query the GenConstrType attribute to determine the type of the general constraint.
See also addGenConstrTan for a description of the semantics of this general constraint type.
genc: The general constraint object.
A tuple (xvar, yvar) that contains the data of the general constraint:
xvar (Var): The variable.
yvar (Var): The variable.