Why Developers Never Use State Machines • Hacker News Board

Re: Why Developers Never Use State Machines

#11

Post by mmahemoff » Thu, Sep 01, 2011, 12:39 PM UTC

State machines are a form of declarative logic as opposed to procedural, and declarative is often superior for modelling real-world activity.

Procedural logic tends to be brittle - small changes have unintended consequences. Declarative models tend to be more robust and, especially with domain-specific languages, safer for domain experts to manipulate. You can certainly design domain-specific languages for the subset of declarative systems that are state machines.

I've happily used state machines in enterprise projects. One was tracking rates of financial instruments, where they would be in various states of validity (i.e. is it a live offer?). Another was a logistics app, where data would move through various states of being cleansed and approved, or rejected. We built a UI around it. By isolating the state definitions and their transitions, it was easy to validate the program's model with business exprts.

Re: Why Developers Never Use State Machines

#12

Post by super_mario » Thu, Sep 01, 2011, 12:40 PM UTC

Simple, because most developers are not computer scientists i.e. no formal training in finite automata, computability, complexity, nondeterminism, regular expressions, non regular languages, context free grammars and languages, Turing machines, halting problem and underlying math in general.

If they did, trust me they would use state machines without too much reservation where appropriate. But as it is, the concept is foreign to most and good ones intuit their way into implementing one perhaps (just guessing here).

Re: Why Developers Never Use State Machines

#13

Post by bmcleod » Thu, Sep 01, 2011, 12:40 PM UTC

I've been adding a state machine whenever I find myself adding a state column for a couple of years now.

I have always found this streamlining at least one change in the couple of months after initial implementation.

Re: Why Developers Never Use State Machines

#14

Post by foobarbazoo » Thu, Sep 01, 2011, 12:53 PM UTC

SproutCore has an entire statechart framework built into it. Not sure where the OP is getting his data...

Re: Why Developers Never Use State Machines

#15

Post by pagekalisedown » Thu, Sep 01, 2011, 12:53 PM UTC

davedx wrote: post #3

This man has never heard of video game A.I. programming :)

I had the same reaction. Almost nothing but FSMs in game AI. Makes me wonder if we need to look beyond FSMs for the next level of intelligence.

Re: Why Developers Never Use State Machines

#16

Post by moondowner » Thu, Sep 01, 2011, 12:53 PM UTC

I (as a Java developer) use state machines often - and know other developers who do same too. I use mostly enums (though there are other ways of achieving it), as explained in this post:

Java Secret: Using an enum to build a State machine: http://vanillajava.blogspot.com/2011/06/java-secret-using-en...

Re: Why Developers Never Use State Machines

#17

Post by moondowner » Thu, Sep 01, 2011, 12:55 PM UTC

JoeAltmaier wrote: post #2

Use them all the time, have for all my career. They organize complex code, dissect complex set-flag-here-and-test-there spaghetti into a matrix of states and events that can be exhaustively examined and debugged. Yes you have to organize your code to feed the machine (Vol is hungry! We must feed Vol!) But you have to organize your code somehow, and feeding a state machine can actually be easier to understand that fla…

True, it's better to have a set of states instead of a dozen boolean values. It gives better code, and better organized databases too.

Re: Why Developers Never Use State Machines

#18

Post by kennu » Thu, Sep 01, 2011, 12:55 PM UTC

I've always used a state machine whenever I've parsed XML using an event based parser (SAX).

Although lately I've been replacing an explicit state variable with a stack containing the current element path, since that's pretty easy to do using modern languages.

Re: Why Developers Never Use State Machines

#19

Post by probablyrobots » Thu, Sep 01, 2011, 12:57 PM UTC

I agree with the discussion here. State machines are very useful. The best thing about them is how easy they makes documentation. You just draw a state diagram and you're done!

Re: Why Developers Never Use State Machines

#20

Post by bradfa » Thu, Sep 01, 2011, 1:15 PM UTC

super_mario wrote: post #12

Simple, because most developers are not computer scientists i.e. no formal training in finite automata, computability, complexity, nondeterminism, regular expressions, non regular languages, context free grammars and languages, Turing machines, halting problem and underlying math in general. If they did, trust me they would use state machines without too much reservation where appropriate. But as it is, the concept i…

It'd be interesting to poll programmers who have computer science degrees, electrical engineering degrees, and are self taught to understand the percentage of each who understands state machines, even just at a basic level.

I'll wager electrical engineers understand state machines more often than the other two categories. Stage machines are rather useful in designing hardware.