 	}
 
 
+	// MARK: Alternation
+
 	let alternation = literal("x") | (literal("y") --> const(1))
 
 	func testAlternationParsesEitherAlternative() {

	}


	// MARK: Nonterminals

	let concatenation = literal("x") ++ literal("y")


		assertEqual((literal("x") | literal("y"))("xy")?.0, "x")
	}


	// MARK: Repetition

	let zeroOrMore = literal("x")*

