Add day 4 solutions

day4.chpl

@@ -0,0 +1,14 @@
+use IO;
+
+iter pairs() {
+  var low1, low2, high1, high2 : int;
+  while readf("%i-%i,%i-%i", low1, high1, low2, high2) do
+    yield (low1..high1, low2..high2);
+}
+
+proc anyContains((r1, r2): 2*range) { return r1.contains(r2) || r2.contains(r1); }
+proc overlap((r1, r2): 2*range) { return !r1[r2].isEmpty(); }
+
+var thePairs = pairs();
+writeln(+ reduce anyContains(thePairs));
+writeln(+ reduce overlap(thePairs));