In what areas of programming would I use a state machine? Use a state machine to represent a (real or logical) object that can exist in a limited number of conditions (“states“) and progresses from one state to the next according to a fixed set of rules. Why would I use a state machine? A … Read more
It’s feasible but it is a bad idea. Iterator blocks were created to help you write custom iterators for collections, not for solving the general-purpose problem of implementing state machines. If you want to write a state machine, just write a state machine. It’s not hard. If you want to write a lot of state … Read more
I don’t really get the question. The State Design pattern is pretty clear. See the Design Patterns book. class SuperState( object ): def someStatefulMethod( self ): raise NotImplementedError() def transitionRule( self, input ): raise NotImplementedError() class SomeState( SuperState ): def someStatefulMethod( self ): actually do something() def transitionRule( self, input ): return NextState() That’s pretty … Read more
There is some catastrophic backtracking going on that will cause an exponential amount of processing depending on how long the non-match string is. This has to do with your nested repetitions and optional comma (even though some regex engines can determine that this wouldn’t be a match with attempting all of the extraneous repetition). This … Read more
State machines are very simple in C if you use function pointers. Basically you need 2 arrays – one for state function pointers and one for state transition rules. Every state function returns the code, you lookup state transition table by state and return code to find the next state and then just execute it. … Read more
A rather convenient way to help look at this to use python’s little-known re.DEBUG flag on any pattern: >>> re.compile(r'<([A-Z][A-Z0-9]*)\b[^>]*>(.*?)</\1>’, re.DEBUG) literal 60 subpattern 1 in range (65, 90) max_repeat 0 65535 in range (65, 90) range (48, 57) at at_boundary max_repeat 0 65535 not_literal 62 literal 62 subpattern 2 min_repeat 0 65535 any None … Read more
The heart of a state machine is the transition table, which takes a state and a symbol (what you’re calling an event) to a new state. That’s just a two-index array of states. For sanity and type safety, declare the states and symbols as enumerations. I always add a “length” member in some way (language-specific) … Read more
Let’s start with this simple state diagram: We have: 4 states (Inactive, Active, Paused, and Exited) 5 types of state transitions (Begin Command, End Command, Pause Command, Resume Command, Exit Command). You can convert this to C# in a handful of ways, such as performing a switch statement on the current state and command, or … Read more
State machines that I’ve designed before (C, not C++) have all come down to a struct array and a loop. The structure basically consists of a state and event (for look-up) and a function that returns the new state, something like: typedef struct { int st; int ev; int (*fn)(void); } tTransition; Then you define … Read more