.. _gettingStartedRecursionDoc:

.. index:: single: Example; Recursion

=========
Recursion
=========

::

	constant Rate { value: 50 }
	signal N { default: 0 rate: Rate }
	signal FactorialResult { default: 0 rate: Rate }

	N >> Factorial () >> FactorialResult;

::

	module Factorial {
		input:		Input
		output:		Output
		propertyName:	none
		propertyBlock:	none
		internalBlock:	[
			signal Input { default: 0 rate: none },
			signal Output { default: 0 rate: none },
			signal Result { default: 0 rate: none reset: Reset },		
			signal Count { default: Input rate: none reset: Reset },
			switch End { default: off reset: Reset },
			switch FlipFlop { default: off reset: none },
			trigger Reset {},
			reaction FactorialReaction {
				output: 	Result
				onExecution:	Reset	
				terminateWhen:	Done
				propertyName:	'value'
				propertyBlock:	signal Value { default: 0 }
				internalBlock:	[
					signal Result { default: 0 rate: none },
					switch Done { default: off reset: Reset },
					trigger Reset {}
				]
				streams:		[
					Value >> Factorial () >> Result;
					on >> Done; 
				]
			}
		]
		streams:		[

			FlipFlop >> Select ( whenOn: off whenOff: on ) >> FlipFlop >> OnEdge (edge: 'Both' ) >> Reset;
			Count >> Compare ( value: 0 operator: 'Equal' ) >> End;
			not End >> FactorialReaction ( value: Count - 1 ) >> Result;
			End >> Select ( whenOn: 1 whenOff: Count * Result ) >> Output;
		]
	}

----

**Python**

.. highlight:: py

::

	def factorial(n):
		if n == 0:
			return 1
		else:
			return n * factorial(n-1)

**C / C++**

.. highlight:: c

::

	unsigned int factorial (unsigned int f) {
	    if (f == 0) {
	        return 1;
	    } else {
	        return f * factorial(f - 1);
	    }
	}