Show HN: Finite State Machine for Go

#1

Post by maxpersson » Thu, Sep 18, 2014, 11:59 AM UTC

Show HN: Finite State Machine for Go
github.com

Re: Show HN: Finite State Machine for Go

#2

Post by untothebreach » Thu, Sep 18, 2014, 12:07 PM UTC

I mostly like this. The only gripe I have with it is the stringly-typed way of triggering events. It seems like you might be able to better leverage the type system to ensure that spelling mistakes or fat-fingerings don't cause a runtime error sometime in the future. If the .Event() method took an object that satisfied the "Trigger" (or something) interface, instead of just a string, you might be able to catch those kinds of errors during compile-time instead.

Re: Show HN: Finite State Machine for Go

#3

Post by maxpersson » Thu, Sep 18, 2014, 12:19 PM UTC

untothebreach wrote: post #2

I mostly like this. The only gripe I have with it is the stringly-typed way of triggering events. It seems like you might be able to better leverage the type system to ensure that spelling mistakes or fat-fingerings don't cause a runtime error sometime in the future. If the .Event() method took an object that satisfied the "Trigger" (or something) interface, instead of just a string, you might be able to catch those…

Thanks for the feedback! It's a good suggestion, and having something else than strings as events is something that I have analyzed. Currently different handlers depends on string operations as selectors, for example "before_". Any ideas on how to move that to the static type world (preferably without using the reflect package)?

Re: Show HN: Finite State Machine for Go

#4

Post by lsllc » Fri, Sep 19, 2014, 3:10 AM UTC

I prefer to use Ragel as a DSL for FSMs, it'll generate Go code along with other languages. Adrian Thurston has done a fantastic job with Ragel.

Zed Shaw wrote a great essay about state charts in Ragel:

http://www.zedshaw.com/essays/ragel_state_charts.html

The official docs:

http://www.complang.org/ragel/ragel-guide-6.8.pdf

Re: Show HN: Finite State Machine for Go

#5

Post by maxpersson » Fri, Sep 19, 2014, 5:23 AM UTC

lsllc wrote: post #4

I prefer to use Ragel as a DSL for FSMs, it'll generate Go code along with other languages. Adrian Thurston has done a fantastic job with Ragel. Zed Shaw wrote a great essay about state charts in Ragel: http://www.zedshaw.com/essays/ragel_state_charts.html The official docs: http://www.complang.org/ragel/ragel-guide-6.8.pdf

That looks really cool, awesome to be able to generate static FSM code. I use my FSM (and started to use Jake Gordon's) when I need a lightweight state variable, a step up from a collection of bools when it starts to get messy with lots of ands and ors.