Title here
Summary here
Enums in Pascal
Our enum type ServerState has an underlying int type. Enumerated types (enums) are data structures that allow us to define a set of named values for a variable. While some languages have built-in support for enums, many can simulate them using other features.
program EnumsExample;
uses SysUtils;
type
ServerState = (StateIdle, StateConnected, StateError, StateRetrying);
var
stateName: array[ServerState] of string = (
'idle',
'connected',
'error',
'retrying'
);
function StateToString(ss: ServerState): string;
begin
StateToString := stateName[ss];
end;
function Transition(s: ServerState): ServerState;
begin
case s of
StateIdle:
Transition := StateConnected;
StateConnected,
StateRetrying:
Transition := StateIdle;
StateError:
Transition := StateError;
else
raise Exception.Create('unknown state: ' + IntToStr(Ord(s)));
end;
end;
var
ns, ns2: ServerState;
begin
ns := Transition(StateIdle);
WriteLn(StateToString(ns));
ns2 := Transition(ns);
WriteLn(StateToString(ns2));
end.The possible values for ServerState are defined as constants of an enumerated type. By using a mapping array, values of ServerState can be printed out or converted to strings.
In the main section, we create a ServerState variable and transition between states. If we try passing a non-ServerState value to the transition function, Pascal will ensure type safety at compile-time, preventing errors.