 	}
 
 
-	// MARK: Nonterminals
+	// MARK: - Nonterminals
+
+	// MARK: Concatenation
 
 	let concatenation = literal("x") ++ literal("y")
 

	}


	let alternation = literal("x") | (literal("y") --> const(1))

	func testAlternationParsesEitherAlternative() {


final class MadnessTests: XCTestCase {

	// MARK: - Terminals

	func testLiteralParsersParseAPrefixOfTheInput() {
		assertEqual(literal("foo")("foot")?.1, "t")
