-- @atlcompiler emftvm
-- @path Graph=/TTC2011/metamodels/graph.ecore
query nrOfCircles = Graph!Graph.allInstances()->first().circles->size().debug('nrOfCircles');

-- Finds the set of all circles of 3 nodes.
helper context Graph!Graph def : circles : Set(Set(Graph!Node)) =
	self.nodes->iterate(n1; acc1 : Set(Set(Graph!Node)) = Set{} | 
		self.nodes->iterate(n2; acc2 : Set(Set(Graph!Node)) = acc1 |
			if n1 <> n2 and self.connected(n1, n2) then
				self.nodes->iterate(n3; acc3 : Set(Set(Graph!Node)) = acc2 |
					if n1 <> n3 and n2 <> n3 and self.connected(n2, n3) and self.connected(n3, n1) then
						acc3->including(Set{n1, n2, n3}.debug('Found circle'))
					else
						acc3
					endif
				).debug('circles(3)')
			else
				acc2
			endif
		).debug('circles(2)')
	).debug('circles');

-- Returns true iff n1 and n2 are connected by an edge in self.
helper context Graph!Graph def : connected(n1 : Graph!Node, n2 : Graph!Node) : Boolean =
	self.edges->exists(e | e.src = n1 and e.trg = n2);