Options

(* `option(T)` is `Some(value)` or `None`. Match it with `case`. *)
 
import "std/evm";
 
storage is record {
  admin : option(address);
}
 
external function appoint() is {
  storage.admin := Some(Evm.sender());
}
 
external function resign() is {
  storage.admin := None;
}
 
external view function adminOr(const fallback : address) : address is
  case storage.admin of {
  | Some(who) -> who
  | None -> fallback
  }
 
external view function hasAdmin() : bool is
  case storage.admin of {
  | Some(who) -> true
  | None -> false
  }