// RESULT: 1
	P=? [ G F "a" ];
	// RESULT: 0.75
	P=? [ (G !"b")&(G F "a") ];
	// RESULT: 0.125
	P=? [ F G "a" ];
	// RESULT: 1
	P=? [ (G ("b"=>(F (!"b"&"a"))))&(F G !"b") ];
	// RESULT: true (should be satisfied by {1,2,5})
	filter(forall, P>0.2 [ F G "a" ], s=1|s=2|s=5);
	// RESULT: true (should be satisfied by {1,2,5})
	filter(count, P>0.2 [ F G "a" ]) = 3;