diff --git a/src/basics/vector.cc b/src/basics/vector.cc
index a3b6fac..76e2b52 100644
--- a/src/basics/vector.cc
+++ b/src/basics/vector.cc
@@ -5,13 +5,19 @@
 
 #include <cmath>
 #include <cstring>
+#include <sstream>
+#include <stdexcept>
 
 #include "basics/vector.hh"
 
+#include "basics/util.hh"
+
 
 namespace charles {
 namespace basics {
 
+#pragma mark Constructors and Assignment
+
 /*
  * charles::basics::Vector4::Vector4 --
  */
@@ -34,6 +40,17 @@ Vector4::Vector4(Double x,
     mData[3] = 1.0;
 }
 
+
+/*
+ * charles::basics::Vector4::operator= --
+ */
+Vector4&
+Vector4::operator=(const Vector4 &rhs)
+{
+    memcpy(mData, rhs.mData, sizeof(Double) * 4);
+    return *this;
+}
+
 #pragma mark Component Access
 
 /*
@@ -98,6 +115,70 @@ Vector4::Z()
     return mData[2];
 }
 
+
+Double&
+Vector4::operator()(UInt i)
+{
+    if (i >= 4) {
+        std::stringstream ss;
+        ss << "vector index out of bounds: i = " << i;
+        throw std::out_of_range(ss.str());
+    }
+    return mData[i];
+}
+
+
+Double
+Vector4::operator()(UInt i)
+    const
+{
+    if (i >= 4) {
+        std::stringstream ss;
+        ss << "vector index out of bounds: i = " << i;
+        throw std::out_of_range(ss.str());
+    }
+    return mData[i];
+}
+
+
+/*
+ * charles::basics::Vector4::CArray --
+ */
+const Double*
+Vector4::CArray()
+    const
+{
+    return mData;
+}
+
+#pragma mark Boolean Operators
+
+/*
+ * charles::basics::Vector4::operator== --
+ */
+bool
+Vector4::operator==(const Vector4 &rhs)
+    const
+{
+    for (UInt i = 0; i < 4; i++) {
+        if (!NearlyEqual(mData[i], rhs.mData[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
+
+/*
+ * charles::basics::Vector4::operator!= --
+ */
+bool
+Vector4::operator!=(const Vector4 &rhs)
+    const
+{
+    return !(*this == rhs);
+}
+
 #pragma mark Maths
 
 /*
diff --git a/src/basics/vector.hh b/src/basics/vector.hh
index a98a095..e8b99a2 100644
--- a/src/basics/vector.hh
+++ b/src/basics/vector.hh
@@ -33,6 +33,12 @@ struct Vector4
     Double  Y() const;
     Double& Z();
     Double  Z() const;
+
+    Double &operator()(UInt i);
+    Double  operator()(UInt i) const;
+
+    /** Get the underlying C array. */
+    const Double *CArray() const;
     /** @} */
 
     bool operator==(const Vector4 &rhs) const;