Module: fsm (Finite State Machines)

Welcome! This is the documentation for the fsm module, part of the asap project. This is a feature module providing a framework to quickly build type safe state machines using C++17 and templates.

A state machine has a set of possible states and a set of rules that govern transitions between the current state and some other state upon receiving an event.

A state can be an arbitrary object, which type is used to distinguish it from other states. Therefore, there is no need to maintain a list of known states (in an enumeration for example). We also don’t want to enforce any relationship between those types to keep them completely independent. The state machine is a variadic template that gets to know its states through the parameter pack and stores them in a tuple.

Transitions from the current state to other states are triggered by events. This requires that all the state types have a Handle method that accepts an event of the type of event being handled. To avoid creating unnecessary dependencies between the state types and the state machine type, a state’s Handle method will return an object of a specific type (an action) that will describe what action should the machine take.

Events are produced outside the state machine and fed into it by an external event loop which calls the state machine’s Handle method. The latter dispatches the event to the current state, which returns a specific action that gets executed to eventually transition to a new state.

Parts of the documentation

API reference

check this out to see the documentation of classes, macros, etc. offered by this module