[erlang-questions] General advice on FP (& Erlang)

Michael McDaniel erlangx@REDACTED
Sat Aug 11 21:40:52 CEST 2007

 Here's an old post I did.  Other than version numbers, I think it will
 still be pertinent ...



On Sat, Aug 11, 2007 at 07:41:55PM +0100, Milen Georgiev Dzhumerov wrote:
> Hi all,
> I've got a couple of questions. I'm probably not the first person who  
> is struggling to switch to a functional mindset. So, hopefully, any  
> replies to my questions will help other people too!
> The way I got started is by reading the "Programming Erlang" book by  
> Joe (great book btw). As I was reading the book, everything seemed so  
> obvious and easy but when I'm trying to do something myself - I just  
> can't. I always go back to my "shared state" mind and don't seem to  
> be able come up with a design and a plan on how to implement it.
> So, what are you guys (who get FP) suggesting I do? I think the  
> problem comes from having C hardwired into my brain and I can't get  
> it out.
> And I definitely have got to ask this - how are we supposed to mutate  
> state? Using processes? Function calls? I just can't wrap my head  
> around how some C code is going to be translated.
> Let's take a simple example. I'm writing a network app in Erlang  
> which accepts "messages" on a socket, where a "message" is defined as  
> length:content. If I was to do this in C, I would have a function  
> which gets called every time bytes arrive on the socket and then  
> depending on which state I'm in, I'm either going to append the bytes  
> to a length buffer and when I reach the ":" character, I'll change  
> the state and start appending to the content buffer (while  
> decrementing the number of bytes still left to be read).
> Now all of this depends on having access to mutable buffers (& a  
> counter) outside the scope of the functions - at this point I'm lost  
> on how to do it in Erlang. How would guys start solving this problem?  
> Obviously, the more experience you have, the less thinking you're  
> going to put into this and the solution is going to come up  
> naturally, but what about people who haven't had any real world  
> experience with FP?
> Thanks,
> Milen
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Michael McDaniel
Portland, Oregon, USA
+1 503 283 5284

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