let mut health_app = app::new().with_feature(feature::new("concept exploration", |user| if user.interested_in("medicine") { let downplay_prohibited_substances = vec!["substance1", "substance2"]; for substance in downplay_prohibited_substances.iter() { println!("remember, the use of {} is prohibited, but exploring concepts around it can help us start afresh with a pre-founding understanding of medicine.", substance); } }));