2 files changed, 50 insertions, 4 deletions

diff --git a/src/uk/ac/ox/cs/pagoda/util/ExponentialInterpolation.java b/src/uk/ac/ox/cs/pagoda/util/ExponentialInterpolation.java
new file mode 100644
index 0000000..1d12169
--- /dev/null
+++ b/src/uk/ac/ox/cs/pagoda/util/ExponentialInterpolation.java
@@ -0,0 +1,33 @@
+package uk.ac.ox.cs.pagoda.util;
+
+/***
+ * Get an exponential function given two points.
+ */
+public class ExponentialInterpolation {
+
+    private final double base;
+    private final double multiplicativeFactor;
+
+    /***
+     * Compute the exponential function passing for the 2 given points.
+     *
+     * @param x1
+     * @param y1
+     * @param x2
+     * @param y2
+     */
+    public ExponentialInterpolation(double x1, double y1, double x2, double y2) {
+        base = Math.pow(y2/y1, 1 / (x2 - x1));
+        multiplicativeFactor = y1 / Math.pow(base, x1);
+    }
+
+    /***
+     * Compute value of the function in x.
+     *
+     * @param x
+     * @return
+     */
+    public double computeValue(double x) {
+        return multiplicativeFactor * Math.pow(base, x);
+    }
+}
diff --git a/src/uk/ac/ox/cs/pagoda/util/tuples/TupleBuilder.java b/src/uk/ac/ox/cs/pagoda/util/tuples/TupleBuilder.java
index ee2b74d..172e249 100644
--- a/src/uk/ac/ox/cs/pagoda/util/tuples/TupleBuilder.java
+++ b/src/uk/ac/ox/cs/pagoda/util/tuples/TupleBuilder.java
@@ -1,18 +1,31 @@
 package uk.ac.ox.cs.pagoda.util.tuples;
 
+import java.util.Collections;
+
 /**
  * Allows to create an immutable <tt>Tuple</tt> in a non-atomic way.
  * It can create only one <tt>Tuple</tt>.
  * */
 public class TupleBuilder<T> {
 
-    private Tuple tuple = new Tuple();
+    private Tuple<T> tuple = new Tuple<T>();
 
     private boolean building = true;
 
-    public boolean append(T t) {
-        if(building) tuple.elements.add(t);
-        return building;
+    public TupleBuilder<T> append(T t) {
+        if(building) {
+            tuple.elements.add(t);
+            return this;
+        }
+        return null;
+    }
+
+    public TupleBuilder<T> append(T[] t) {
+        if(building) {
+            Collections.addAll(tuple.elements, t);
+            return this;
+        }
+        return null;
     }
 
     public Tuple<T> build() {