tasks a-s

Task/Partial-function-application/Java/partial-function-application-2.java

@@ -0,0 +1,43 @@
+import java.util.Arrays;
+import java.util.function.Function;
+
+public class PartialApplication {
+	// Original method fs(f, s).
+	static Integer[] fs(Function<Integer, Integer> f, Integer[] s) {
+		Integer[] r = new Integer[s.length];
+		for (int i = 0; i < s.length; i++)
+			r[i] = f.apply(s[i]);
+		return r;		
+	}
+
+	// Curried method fs(f).apply(s),
+	// necessary for partial application.
+	static Function<Integer[], Integer[]> fs(Function<Integer, Integer> f) {
+		return s -> fs(f, s);
+	}
+
+	static Function<Integer, Integer> f1 = i -> i * 2;
+
+	static Function<Integer, Integer> f2 = i -> i * i;
+
+	static Function<Integer[], Integer[]> fsf1 = fs(f1); // Partial application.
+
+	static Function<Integer[], Integer[]> fsf2 = fs(f2);
+
+	public static void main(String[] args) {
+		Integer[][] sequences = {
+			{ 0, 1, 2, 3 },
+			{ 2, 4, 6, 8 },
+		};
+
+		for (Integer[] array : sequences) {
+			System.out.printf(
+			    "array: %s\n" +
+			    "  fsf1(array): %s\n" +
+			    "  fsf2(array): %s\n",
+			    Arrays.toString(array),
+			    Arrays.toString(fsf1.apply(array)),
+			    Arrays.toString(fsf2.apply(array)));
+		}
+	}
+}