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Philed

  • About: I blog about Perl.
  • Commented on Writing State Monads in Ocaml
    Ack. Of course. “Initial state” is a better term. So here’s a question: what happens when we want to allow the state to be uninitialised? In most languages, the answer is obvious: we just set the variable to null. But,...
  • Commented on Writing State Monads in Ocaml
    In Haskell, it’s just a parameter to “runState”. I think what you’re trying to do is avoid the need for this parameter and just have a default value. But I think in that case you want to use option, and...
  • Commented on Writing State Monads in Ocaml
    Hey Chris. I think this is a great way to learn monads. There’s probably a fancy way to explain the implementation of “get” and “put”. Maybe it’d help to write “modify”. The purpose of modify is to mutate the state...
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  • cyocum commented on Writing State Monads in Ocaml

    Hi Phil,

    Thanks for this! I am still unsure about the empty. How do I fire the function in that case without something of the proper time to pass in?

  • cyocum commented on Writing State Monads in Ocaml

    So I think I have figured it out. Basically what I am calling “empty” is what Haskell calls “initial state”. I force the user of StateMonad to know what the inital state is when they define the module. I am OK with this. I will just rename the value to reflect this.

    I am still interested in the option route as well though. I tried to implemented but the type checker went a bit crazy so I will need to think about it more before I try it again.

    Thanks!

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