3 ms·

I have coded a number of FSMs. I think the challenge is always in how much performance you want verse flexibility.

• Const-me 9y ago
  I think the challenge is quadratic growth of complexity with state size. Here’s an example of FSM with relatively complex state, 1000-lines gc_execute_line function, it’s for CNC: https://github.com/grbl/grbl/blob/master/grbl/gcode.c https://github.com/grbl/grbl/blob/master/grbl/gcode.c That’s not my code, but I’m not sure I would be able to do much better than that.
  • Jtsummers 9y ago
    That code actually has me a bit confused. I don't understand how this part is working: switch(letter) { case 'G': switch(int_value) { case 4: switch(int_value) { // int_value hasn't changed case 10: ... // so how do we get to this case? That second switch on int_value is at line 151. Have I missed something in the code where int_value is changing?
    • Const-me 9y ago
      It’s not changing. However, above that “case 4:” there’re another cases, “case 10: case 28: case 30: case 92: ” without break at the end of the code. Unlike some other languages, in C and C++ this means execution continues to the next case. The behavior is called "switch statement fallthrough". That source code has the comment saying “No break. Continues to next line.”
      • Jtsummers 9y ago
        Ah, I missed that they didn't break above it. Thanks.