Implemented clone.

src/main/java/ee/ut/cs/gitlab/maikov/expressions/MatrixValue.java

@@ -78,4 +78,9 @@ public class MatrixValue extends Value {
     public String toString() {
         return matrix.toString();
     }
+
+    @Override
+    public Value clone() {
+        return new MatrixValue(Matrix.clone(this.matrix));
+    }
 }

src/main/java/ee/ut/cs/gitlab/maikov/expressions/Number.java

@@ -64,4 +64,9 @@ public class Number extends Value {
     public String toString() {
         return Double.toString(number);
     }
+
+    @Override
+    public Value clone() {
+        return new Number(this.number);
+    }
 }

src/main/java/ee/ut/cs/gitlab/maikov/expressions/Value.java

@@ -2,6 +2,8 @@ package ee.ut.cs.gitlab.maikov.expressions;
 
 public abstract class Value extends Expression implements MathOp {
 
+    public abstract Value clone();
+
     @Override
     public Expression compute() {
         return this;