Comments on: Dear Java guy, State is a monad http://blog.tmorris.net/dear-java-guy-state-is-a-monad/ The weblog of Tony Morris Sat, 04 Feb 2012 12:54:00 +0000 http://wordpress.org/?v=2.6 By: Marco Faustinelli http://blog.tmorris.net/dear-java-guy-state-is-a-monad/#comment-43490 Marco Faustinelli Tue, 27 Jul 2010 07:14:20 +0000 http://blog.tmorris.net/?p=634#comment-43490 Good morning Tony. Actually I believe me and many others would appreciate to read a specific answer to the specific question from John Nilsson. Why/when is this better than Java's language-specific state support? I already know a monad is a fluffy cloud, but generic messages like these don't actually increase my sense of urgency about learning and applying in my day job such a complex matter. Thanks in advance and have a nice day, Marco Good morning Tony. Actually I believe me and many others would appreciate to read a specific answer to the specific question from John Nilsson. Why/when is this better than Java’s language-specific state support? I already know a monad is a fluffy cloud, but generic messages like these don’t actually increase my sense of urgency about learning and applying in my day job such a complex matter.
Thanks in advance and have a nice day,
Marco

]]> By: Tony Morris http://blog.tmorris.net/dear-java-guy-state-is-a-monad/#comment-36424 Tony Morris Wed, 20 Jan 2010 23:53:05 +0000 http://blog.tmorris.net/?p=634#comment-36424 Hello John, I hope to partially answer that question when I get a chance in another post. Specifically, the question Why Does Monad Matter? All I wanted to do here is witness that State (with a universally quantified type variable) is itself a monad. Hello John,
I hope to partially answer that question when I get a chance in another post. Specifically, the question Why Does Monad Matter?

All I wanted to do here is witness that State (with a universally quantified type variable) is itself a monad.

]]> By: John Nilsson http://blog.tmorris.net/dear-java-guy-state-is-a-monad/#comment-36423 John Nilsson Wed, 20 Jan 2010 23:14:15 +0000 http://blog.tmorris.net/?p=634#comment-36423 I'm struggling to see _why_ to use this thing. Honestly, if there is a reason I'd like to know. In essence my question is, when is this better than using Javas native support for state? Like the comment in the Scala example you linked to. I’m struggling to see _why_ to use this thing.
Honestly, if there is a reason I’d like to know.

In essence my question is, when is this better than using Javas native support for state? Like the comment in the Scala example you linked to.

]]> By: Tony Morris http://blog.tmorris.net/dear-java-guy-state-is-a-monad/#comment-36402 Tony Morris Wed, 20 Jan 2010 01:20:13 +0000 http://blog.tmorris.net/?p=634#comment-36402 Hi mate, Consider that State is a function: <code>S -> (S, A)</code>. I have given examples on here before in other languages: http://blog.tmorris.net/the-state-monad-for-scala-users/ Consider that there exists a function: <code>(S -> S) -> A -> State<S, A></code> then think of all the possibilities for the first argument, then try to use the resulting function. e.g. suppose <code>+1</code>, then you have a function <code>A -> State<Int, A></code> which is the same as <code>A -> Int -> (Int, A)</code> which is isomorphic (by curry/uncurry and flip) to <code>(Int, A) -> (Int, A)</code>. Is this a useful function? It looks like a loop that computes values while implicitly adding the value 1 as it recurses don't you think? Try to use it for something useful. Hi mate,
Consider that State is a function: S -> (S, A). I have given examples on here before in other languages: http://blog.tmorris.net/the-state-monad-for-scala-users/

Consider that there exists a function: (S -> S) -> A -> State<S, A> then think of all the possibilities for the first argument, then try to use the resulting function. e.g. suppose +1, then you have a function A -> State<Int, A> which is the same as A -> Int -> (Int, A) which is isomorphic (by curry/uncurry and flip) to (Int, A) -> (Int, A).

Is this a useful function? It looks like a loop that computes values while implicitly adding the value 1 as it recurses don’t you think? Try to use it for something useful.

]]> By: Steven Shaw http://blog.tmorris.net/dear-java-guy-state-is-a-monad/#comment-36389 Steven Shaw Tue, 19 Jan 2010 14:00:58 +0000 http://blog.tmorris.net/?p=634#comment-36389 Tony, I'm struggling to see how to use this thing. Can see how the S threads through but what is a good type for S? http://github.com/steshaw/playground/blob/master/java/state-is-a-monad/StateMonadExample.java a Java guy Tony, I’m struggling to see how to use this thing. Can see how the S threads through but what is a good type for S?

http://github.com/steshaw/playground/blob/master/java/state-is-a-monad/StateMonadExample.java

a Java guy

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