Equations
- b.append_list (v :: vs) = (b.push_back v).append_list vs
 - b.append_list list.nil = b
 
Equations
- b.append_string s = b.append_list s.to_list
 
@[protected, instance]
    Equations
- buffer.has_mem = {mem := buffer.mem α}
 
@[protected, instance]
    Equations
@[protected, instance]