Lazy Evaluation in F#

(In learning from "Programming F# 3.0, 2nd Edition")

Define lazy instance

These two are completely same way.

> let current = lazy(System.DateTime.Now);;

val current : Lazy<System.DateTime> = Value is not created.

> let current = Lazy<System.DateTime>.Create(fun() -> System.DateTime.Now);;

val current : System.Lazy<System.DateTime> = Value is not created.

Evaluate lazy instance

These two are also completely same way.

> current.IsValueCreated;;
val it : bool = false
> current.Value;;
val it : System.DateTime = 2013/02/04 20:40:19 {Date = 2013/02/04 0:00:00;
                                                Day = 4;
                                                DayOfWeek = Monday;
                                                DayOfYear = 35;
                                                Hour = 20;
                                                Kind = Local;
                                                Millisecond = 676;
                                                Minute = 40;
                                                Month = 2;
                                                Second = 19;
                                                Ticks = 634956072196762680L;
                                                TimeOfDay = 20:40:19.6762680;
                                                Year = 2013;}
> current.IsValueCreated;;
val it : bool = true
> current.Value;;
val it : System.DateTime = 2013/02/04 20:40:19 {Date = 2013/02/04 0:00:00;
                                                Day = 4;
                                                DayOfWeek = Monday;
                                                DayOfYear = 35;
                                                Hour = 20;
                                                Kind = Local;
                                                Millisecond = 676;
                                                Minute = 40;
                                                Month = 2;
                                                Second = 19;
                                                Ticks = 634956072196762680L;
                                                TimeOfDay = 20:40:19.6762680;
                                                Year = 2013;}

> current.IsValueCreated;;
val it : bool = false
> current.Force();;
val it : System.DateTime = 2013/02/04 20:40:19 {Date = 2013/02/04 0:00:00;
                                                Day = 4;
                                                DayOfWeek = Monday;
                                                DayOfYear = 35;
                                                Hour = 20;
                                                Kind = Local;
                                                Millisecond = 676;
                                                Minute = 40;
                                                Month = 2;
                                                Second = 19;
                                                Ticks = 634956072196762680L;
                                                TimeOfDay = 20:40:19.6762680;
                                                Year = 2013;}
> current.IsValueCreated;;
val it : bool = true
> current.Force();;
val it : System.DateTime = 2013/02/04 20:40:19 {Date = 2013/02/04 0:00:00;
                                                Day = 4;
                                                DayOfWeek = Monday;
                                                DayOfYear = 35;
                                                Hour = 20;
                                                Kind = Local;
                                                Millisecond = 676;
                                                Minute = 40;
                                                Month = 2;
                                                Second = 19;
                                                Ticks = 634956072196762680L;
                                                TimeOfDay = 20:40:19.6762680;
                                                Year = 2013;}