isInt = true
				}
			default:
				// Already 0, false.
			}
		}
		newArgNum = argNum + 1
		if tooLarge(num) {
			num = 0
			isInt = false
		}
	}
	return
}

// parseArgNumber returns the value of the bracketed number, minus 1
// (explicit argument numbers are one-indexed but we want zero-indexed).
// The opening bracket is known to be present at format[0].