1,2,3

Author: igr

java/src/main/java/v/o/i/d/monadsplain/One.java

@@ -0,0 +1,18 @@
+package v.o.i.d.monadsplain;
+
+public class One {
+
+	public Integer square(Integer i) {
+		return i * i;
+	}
+	public Integer addOne(Integer i) {
+		return i + 1;
+	}
+
+	public void run() {
+		System.out.println(addOne(square(3)));
+	}
+	public static void main(String[] args) {
+		new One().run();
+	}
+}

java/src/main/java/v/o/i/d/monadsplain/Three.java

@@ -0,0 +1,50 @@
+package v.o.i.d.monadsplain;
+
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+public class Three {
+
+	public static class IntegerWithHistory {
+		public final Integer value;
+		public final String[] history;
+
+		public IntegerWithHistory(Integer value, String[] history) {
+			this.value = value;
+			this.history = history;
+		}
+
+		public static IntegerWithHistory wrap(Integer i) {
+			return new IntegerWithHistory(i, new String[] {});
+		}
+	}
+
+	public IntegerWithHistory square(IntegerWithHistory i) {
+		return new IntegerWithHistory(
+				i.value * i.value,
+				join(i.history, "square: " + i.value)
+		);
+	}
+
+	public IntegerWithHistory addOne(IntegerWithHistory i) {
+		return new IntegerWithHistory(
+				i.value + 1,
+				join(i.history, "addOne: " + i.value)
+		);
+	}
+
+	public void run() {
+		IntegerWithHistory i = addOne(square(IntegerWithHistory.wrap(3)));
+		System.out.println(i.value);
+		System.out.println(Arrays.toString(i.history));
+	}
+
+	public static void main(String[] args) {
+		new Three().run();
+	}
+
+	private static String[] join(String[] array, String element) {
+		return Stream.concat(Arrays.stream(array), Stream.of(element)).toArray(String[]::new);
+	}
+
+}

java/src/main/java/v/o/i/d/monadsplain/Two.java

@@ -0,0 +1,27 @@
+package v.o.i.d.monadsplain;
+
+public class Two {
+	public static class IntegerWithHistory {
+		public final Integer value;
+		public final String[] messages;
+
+		public IntegerWithHistory(Integer value, String[] messages) {
+			this.value = value;
+			this.messages = messages;
+		}
+	}
+
+	public IntegerWithHistory square(Integer i) {
+		return new IntegerWithHistory(
+				i * i,
+				new String[] {"square: " + i}
+		);
+	}
+	public IntegerWithHistory addOne(Integer i) {
+		return new IntegerWithHistory(
+				i + 1,
+				new String[] {"addOne: " + i}
+		);
+	}
+
+}