public class Lens {
	public static Pair[] get(String[] source) {
		// ADD CODE HERE
	}
	
	public static String[] create(Pair[] view) {
		// ADD CODE HERE
	}
	
	public static String[] put(String[] oldSource, Pair[] newView) {
		// Check that the old source and new view have same length.
		// If they do not, report an error and stop the whole program.
		if (!(oldSource.length == newView.length)) {
			throw new RuntimeException("Length of view and source didn't match");
		}
		// if we get here at all, we know oldSource.length == newView.length
		// ADD CODE HERE
	}
}