fn require(&self, cond: bool, msg: &str) {
        if !cond {
            panic(msg)
        }
    }
// panics if condition is not satisfied
panics if condition is not satisfied
panics if condition is not satisfied
fn require(&self, cond: bool, msg: &str) {
        if !cond {
            panic(msg)
        }
    }
fn require ( & self , cond : bool , msg : & str ) { if ! cond { panic ( msg ) } }
panics if condition is not satisfied
panics if condition is not satisfied
&self
cond
bool
msg
&str