diff --git a/src/main/java/oving5/RPNCalc.java b/src/main/java/oving5/RPNCalc.java
index 289f843..749b5cc 100644
--- a/src/main/java/oving5/RPNCalc.java
+++ b/src/main/java/oving5/RPNCalc.java
@@ -1,25 +1,65 @@
 package oving5;
 
 import java.util.function.BinaryOperator;
+import java.util.Stack;
+import java.util.HashMap;
 
 public class RPNCalc {
+	private HashMap<Character, BinaryOperator<Double>> ops = new HashMap<Character, BinaryOperator<Double>>();
+	private Stack<Double> stack = new Stack<>();
+
 	RPNCalc() {
 	}
 
-	public void performOperation(char c) {
+	boolean addOperator(char op, BinaryOperator<Double> f) {
+		if (ops.containsKey(op) || f == null) {
+			return false;
+		}
+		ops.put(op, f);
+		return true;
 	}
 
-	public void removeOperator(char c) {
+	void push(double n) {
+		stack.push(n);
 	}
 
-	public boolean addOperator(char c, BinaryOperator<Double> d) {
-		return false;
+	double pop() {
+		if (stack.isEmpty()) {
+			return Double.NaN;
+		}
+		return stack.pop();
 	}
 
-	public Double pop() {
-		return 0.0;
+	double peek(int i) {
+		int id = stack.size() - i;
+		if (id < 0 || id >= stack.size()) {
+			return Double.NaN;
+		}
+		return stack.get(id);
 	}
 
-	public void push(int i) {
+	int getSize() {
+		return stack.size();
 	}
+
+	void performOperation(char c) {
+		BinaryOperator<Double> op = ops.get(c);
+
+		if (op == null) {
+			throw new UnsupportedOperationException("Invalid operator: " + c);
+		}
+
+		if (stack.size() <= 1) {
+			return;
+		}
+		double a = stack.pop();
+		double b = stack.pop();
+
+		stack.push(op.apply(b, a));
+	}
+
+	void removeOperator(char c) {
+		ops.remove(c);
+	}
+
 }
diff --git a/src/main/java/oving5/named/Named.java b/src/main/java/oving5/named/Named.java
new file mode 100644
index 0000000..a597540
--- /dev/null
+++ b/src/main/java/oving5/named/Named.java
@@ -0,0 +1,10 @@
+package oving5.named;
+
+public interface Named {
+	String getFullName();
+	String getFamilyName();
+	String getGivenName();
+	void setGivenName(String name);
+	void setFamilyName(String name);
+	void setFullName(String name);
+}
diff --git a/src/main/java/oving5/named/NamedComparator.java b/src/main/java/oving5/named/NamedComparator.java
new file mode 100644
index 0000000..b59176c
--- /dev/null
+++ b/src/main/java/oving5/named/NamedComparator.java
@@ -0,0 +1,14 @@
+package oving5.named;
+
+import java.util.Comparator;
+
+public class NamedComparator implements Comparator<Named> {
+	@Override
+	public int compare(Named named1, Named named2) {
+		int a = named1.getFamilyName().compareTo(named2.getFamilyName());
+		if (a == 0) {
+			return named1.getGivenName().compareTo(named2.getGivenName());
+		}
+		return a;
+	}
+}
diff --git a/src/main/java/oving5/named/Person1.java b/src/main/java/oving5/named/Person1.java
index 46ce63f..f785e56 100644
--- a/src/main/java/oving5/named/Person1.java
+++ b/src/main/java/oving5/named/Person1.java
@@ -1,28 +1,43 @@
 package oving5.named;
 
-public class Person1 {
-	Person1(String s) {
+public class Person1 implements Named {
+	private String givenName;
+	private String familyName;
+	private String fullName;
+
+	Person1(String givenName, String familyName) {
+		setFullName(givenName + " " + familyName);
+		setGivenName(givenName);
+		setFamilyName(familyName);
 	}
 
-	public void setFullName(String s) {
+	public void setFullName(String fullName) {
+		this.fullName = fullName;
+		String[] l = fullName.split(" ");
+		givenName = (l[0]);
+		familyName = (l[1]);
 	}
 
-	public void setFamilyName(String s) {
+	public void setFamilyName(String familyName) {
+		this.familyName = familyName;
+		setFullName(givenName + " " + familyName);
 	}
 
-	public void setGivenName(String s) {
+	public void setGivenName(String givenName) {
+		this.givenName = givenName;
+		setFullName(givenName + " " + familyName);
 	}
 
 	public String getFullName() {
-		return "";
+		return fullName;
 	}
 
 	public String getFamilyName() {
-		return "";
+		return familyName;
 	}
 
 	public String getGivenName() {
-		return "";
+		return givenName;
 	}
 
 }
diff --git a/src/main/java/oving5/named/Person2.java b/src/main/java/oving5/named/Person2.java
index 76d62d2..9c67921 100644
--- a/src/main/java/oving5/named/Person2.java
+++ b/src/main/java/oving5/named/Person2.java
@@ -1,28 +1,41 @@
 package oving5.named;
 
-public class Person2 {
-	Person2(String s) {
+public class Person2 implements Named {
+	private String fullName;
+	private String familyName;
+	private String givenName;
+
+	Person2(String fullName) {
+		setFullName(fullName);
 	}
 
-	public void setFullName(String s) {
+	public void setFullName(String fullName) {
+		this.fullName = fullName;
+		String[] l = fullName.split(" ");
+		givenName = l[0];
+		familyName = l[1];
 	}
 
-	public void setFamilyName(String s) {
+	public void setFamilyName(String familyName) {
+		this.familyName = familyName;
+		fullName = givenName + " " + familyName;
 	}
 
-	public void setGivenName(String s) {
+	public void setGivenName(String givenName) {
+		this.givenName = givenName;
+		fullName = givenName + " " + familyName;
 	}
 
 	public String getFullName() {
-		return "";
+		return fullName;
 	}
 
 	public String getFamilyName() {
-		return "";
+		return familyName;
 	}
 
 	public String getGivenName() {
-		return "";
+		return givenName;
 	}
 
 }
diff --git a/src/test/java/oving5/RPNCalcTest.java.unimplemented b/src/test/java/oving5/RPNCalcTest.java
similarity index 100%
rename from src/test/java/oving5/RPNCalcTest.java.unimplemented
rename to src/test/java/oving5/RPNCalcTest.java
diff --git a/src/test/java/oving5/named/NamedComparatorTest.java.unimplemented b/src/test/java/oving5/named/NamedComparatorTest.java
similarity index 100%
rename from src/test/java/oving5/named/NamedComparatorTest.java.unimplemented
rename to src/test/java/oving5/named/NamedComparatorTest.java
diff --git a/src/test/java/oving5/named/Person1Test.java.unimplemented b/src/test/java/oving5/named/Person1Test.java
similarity index 100%
rename from src/test/java/oving5/named/Person1Test.java.unimplemented
rename to src/test/java/oving5/named/Person1Test.java
diff --git a/src/test/java/oving5/named/Person2Test.java.unimplemented b/src/test/java/oving5/named/Person2Test.java
similarity index 100%
rename from src/test/java/oving5/named/Person2Test.java.unimplemented
rename to src/test/java/oving5/named/Person2Test.java