Declare Functions in Reason

What do you mean with avoid a lot of tedious switch expressions (06:53)? The example uses a function with a switch in it, can you please provide another example?

The example uses ~middleName=?someName. Without that you would need to switch on someName. Does that help?

I believe the behaviour described in the video has become outdated.

In the latest version of rtop (2.2.0), I get the following output:

Reason # let name = (~firstName, ~middleName="Francis", ~lastName) => {
  firstName ++ " " ++ middleName ++ " " ++ lastName;
};
let name:
  (~firstName: string, ~middleName: string=?, ~lastName: string) => string =
  <fun>;
Reason # name(~firstName="Jane", ~middleName="Kim", ~lastName="Doe");
- : string = "Jane Kim Doe"
Reason # name(~firstName="Jane", ~lastName="Doe");
- : (~middleName: string=?) => string = <fun>
Reason # name(~firstName="Jane", ~lastName="Doe")();
Error: The function applied to this argument has type
         (~middleName: string=?) => string
This argument cannot be applied without label
Reason # name(~firstName="Jane", ~lastName="Doe", ());
Error: The function applied to this argument has type
         (~middleName: string=?) => string
This argument cannot be applied without label

sorry, please ignore the above comment, I didn't notice the positional parameter () at the end! ```name(~firstName="Jane", ~middleName="Kim", ~lastName="Doe", ());`