Functional Command Pattern
Command pattern is a pattern which allows executor of the pattern to execute or playback the commands. In most of the application wherever Undo/Redo is implemented this pattern is used.
Here is C# code.
Now, in this code Command Pattern is not in its purest form. As, normally in command pattern we are saving state of outside object. Instead I just returned the result to mock out side object.
Now have a look at similar F# code. That is doing kinda same thing.
Here, instead of class I am using functions with the command type. And definition of the command is given as type instead of interface. Now, this is fun with functional programming in general where functions are first class citizen. I can save commands and events like objects only. I don’t have to wrap around some classes. This makes code more concise.