Fun with States

Previously...

• I encountered a problem with my test data.
• I resolved some problems with lists and test data.
• I resolved some problems with dictionaries.

The next problem that I resolved had embarrassingly little to do with the erlang libraries.  With "imperative" languages like Java I am used to doing something like this:

int foo = 1;

foo++; // foo now has the value 2

Whereas with a functional language like erlang, one instead uses something like this:

Foo = 1;

Foo2 = 1 + Foo;

This is because in languages like erlang, you cannot change a variable once it has been set.  Personally, I don't think one should use the term "variable" to describe such an object in erlang, but I digress.

The problem I was running into was that I was not updating the variable that I changed.  Thus I would use something like this:

put_data(State, ConnectionID, Data) ->

    NewState = update_table(State, ConnectionID, Data),

    { Result, NewerState } = remove_waiter(ConnectionID, NewState),

    case Result of

        undefined -> NewerState;

        Waiter -> notify_waiter(Waiter, ConnectionID, State)

    end.

Whereas what I really wanted was something like this:

put_data(State, ConnectionID, Data) ->

    NewState = update_table(State, ConnectionID, Data),

    { Result, NewerState } = remove_waiter(ConnectionID, NewState),

    case Result of

        undefined -> NewerState;

        Waiter -> notify_waiter(Waiter, ConnectionID, NewerState)

    end.

Nothing really Earth shattering here, just ye basic functional vs. imperative programming styles.  This will not stop me from complaining, but I'm just saying...

Next time: more testing goodness.