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Cake day: June 20th, 2023

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  • The recorder. It’s easy to get started, there is a lot of good information online (look up Sarah Jeffery), and professional plastic instruments are very cheap. It also requires no special care and doesn’t need maintenance, since it has no moving parts.

    The downside is that in order to play larger recorders your hands need to stretch a bit, so I’m no sure if that is a problem if you have joint issues.

    The other option is a hand ocarina, but it is very hard to even make a sound, even harder to make it clear and consistent. Also you need to play entirety by ear. It’s a fun challenge, though.














  • Nope. Monads enable you to redefine how statements work.

    Let’s say you have a program and use an Error[T] data type which can either be Ok {Value: T} or Error:

    var a = new Ok {Value = 1};
    var b = foo();
    return new Ok {Value = (a + b)};
    

    Each statement has the following form:

    var a = expr;
    rest
    

    You first evaluate the “expr” part and bind/store the result in variable a, and evaluate the “rest” of the program.

    You could represent the same thing using an anonymous function you evaluate right away:

    (a => rest)(expr);
    

    In a normal statement you just pass the result of “expr” to the function directly. The monad allows you to redefine that part.

    You instead write:

    bind((a => rest), expr);
    

    Here “bind” redefines how the result of expr is passed to the anonymous function.

    If you implement bind as:

    B bind(Func[A, B] f, A result_expr) {
       return f(result_expr);
    }
    

    Then you get normal statements.

    If you implement bind as:

    Error[B] bind(Func[A, Error[B]] f, Error[A] result_expr) {
       switch (result_expr) {
           case Ok { Value: var a}:
               return f(a);
           case Error:
               return Error;
       }
    }
    

    You get statements with error handling.

    So in an above example if the result of foo() is Error, the result of the statement is Error and the rest of the program is not evaluated. Otherwise, if the result of foo() is Ok {Value = 3}, you pass 3 to the rest of the program and you get a final result Ok {Value = 4}.

    So the whole idea is that you hide the if Error part by redefining how the statements are interpreted.