env.addFunction(GetInitialEnrollmentDateFunction.name, new GetInitialEnrollmentDateFunction(userCourseEnv));
env.addFunction(GetRecentEnrollmentDateFunction.name, new GetRecentEnrollmentDateFunction(userCourseEnv));
// functions to calculate score
env.addFunction(GetPassedFunction.name, new GetPassedFunction(userCourseEnv));
env.addFunction(GetScoreFunction.name, new GetScoreFunction(userCourseEnv));
env.addFunction(GetPassedWithCourseIdFunction.name, new GetPassedWithCourseIdFunction(userCourseEnv));
env.addFunction(GetScoreWithCourseIdFunction.name, new GetScoreWithCourseIdFunction(userCourseEnv));
// units
env.addUnit("min", new MinuteUnit());