Editing Mutual recursion (section)

====Advanced examples====
A more complicated example is given by [[recursive descent parser]]s, which can be naturally implemented by having one function for each [[Production (computer science)|production rule]] of a grammar, which then mutually recurse; this will in general be multiple recursion, as production rules generally combine multiple parts. This can also be done without mutual recursion, for example by still having separate functions for each production rule, but having them called by a single controller function, or by putting all the grammar in a single function.

Mutual recursion can also implement a [[finite-state machine]], with one function for each state, and single recursion in changing state; this requires tail call optimization if the number of state changes is large or unbounded. This can be used as a simple form of [[cooperative multitasking]]. A similar approach to multitasking is to instead use [[coroutine]]s which call each other, where rather than terminating by calling another routine, one coroutine yields to another but does not terminate, and then resumes execution when it is yielded back to. This allows individual coroutines to hold state, without it needing to be passed by parameters or stored in shared variables.

There are also some algorithms which naturally have two phases, such as [[minimax]] (min and max), which can be implemented by having each phase in a separate function with mutual recursion, though they can also be combined into a single function with direct recursion.