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diff --git a/src/cml/matrix/matrix_mul.h b/src/cml/matrix/matrix_mul.h
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+/* -*- C++ -*- ------------------------------------------------------------
+ 
+Copyright (c) 2007 Jesse Anders and Demian Nave http://cmldev.net/
+
+The Configurable Math Library (CML) is distributed under the terms of the
+Boost Software License, v1.0 (see cml/LICENSE for details).
+
+ *-----------------------------------------------------------------------*/
+/** @file
+ *  @brief Multiply two matrices.
+ *
+ * @todo Does it make sense to put mat-mat multiplication as a node into the
+ * expression tree?
+ *
+ * @internal This does not need to return an expression type, since the
+ * temporary generation for the matrix result is handled automatically by the
+ * compiler.  i.e. when used in an expression, the result is automatically
+ * included in the expression tree as a temporary by the compiler.
+ */
+
+#ifndef	matrix_mul_h
+#define	matrix_mul_h
+
+#include <cml/et/size_checking.h>
+#include <cml/matrix/matrix_expr.h>
+
+/* This is used below to create a more meaningful compile-time error when
+ * mul is not provided with matrix or MatrixExpr arguments:
+ */
+struct mul_expects_matrix_args_error;
+
+/* This is used below to create a more meaningful compile-time error when
+ * fixed-size arguments to mul() have the wrong size:
+ */
+struct mul_expressions_have_wrong_size_error;
+
+namespace cml {
+namespace detail {
+
+/** Verify the sizes of the argument matrices for matrix multiplication.
+ *
+ * @returns a matrix_size containing the size of the resulting matrix.
+ */
+template<typename LeftT, typename RightT> inline matrix_size
+MatMulCheckedSize(const LeftT&, const RightT&, fixed_size_tag)
+{
+    CML_STATIC_REQUIRE_M(
+            ((size_t)LeftT::array_cols == (size_t)RightT::array_rows),
+            mul_expressions_have_wrong_size_error);
+    return matrix_size(LeftT::array_rows,RightT::array_cols);
+}
+
+/** Verify the sizes of the argument matrices for matrix multiplication.
+ *
+ * @returns a matrix_size containing the size of the resulting matrix.
+ */
+template<typename LeftT, typename RightT> inline matrix_size
+MatMulCheckedSize(const LeftT& left, const RightT& right, dynamic_size_tag)
+{
+    matrix_size left_N = left.size(), right_N = right.size();
+    et::GetCheckedSize<LeftT,RightT,dynamic_size_tag>()
+        .equal_or_fail(left_N.second, right_N.first); /* cols,rows */
+    return matrix_size(left_N.first, right_N.second); /* rows,cols */
+}
+
+
+/** Matrix multiplication.
+ *
+ * Computes C = A x B (O(N^3), non-blocked algorithm).
+ */
+template<class LeftT, class RightT>
+inline typename et::MatrixPromote<
+    typename et::ExprTraits<LeftT>::result_type,
+    typename et::ExprTraits<RightT>::result_type
+>::temporary_type
+mul(const LeftT& left, const RightT& right)
+{
+    /* Shorthand: */
+    typedef et::ExprTraits<LeftT> left_traits;
+    typedef et::ExprTraits<RightT> right_traits;
+    typedef typename left_traits::result_type left_result;
+    typedef typename right_traits::result_type right_result;
+
+    /* First, require matrix expressions: */
+    CML_STATIC_REQUIRE_M(
+            (et::MatrixExpressions<LeftT,RightT>::is_true),
+            mul_expects_matrix_args_error);
+    /* Note: parens are required here so that the preprocessor ignores the
+     * commas.
+     */
+
+    /* Deduce size type to ensure that a run-time check is performed if
+     * necessary:
+     */
+    typedef typename et::MatrixPromote<
+        typename left_traits::result_type,
+        typename right_traits::result_type
+    >::type result_type;
+    typedef typename result_type::size_tag size_tag;
+
+    /* Require that left has the same number of columns as right has rows.
+     * This automatically checks fixed-size matrices at compile time, and
+     * throws at run-time if the sizes don't match:
+     */
+    matrix_size N = detail::MatMulCheckedSize(left, right, size_tag());
+
+    /* Create an array with the right size (resize() is a no-op for
+     * fixed-size matrices):
+     */
+    result_type C;
+    cml::et::detail::Resize(C, N);
+
+    /* XXX Specialize this for fixed-size matrices: */
+    typedef typename result_type::value_type value_type;
+    for(size_t i = 0; i < left.rows(); ++i) {               /* rows */
+        for(size_t j = 0; j < right.cols(); ++j) {          /* cols */
+            value_type sum(left(i,0)*right(0,j));
+            for(size_t k = 1; k < right.rows(); ++k) {
+                sum += (left(i,k)*right(k,j));
+            }
+            C(i,j) = sum;
+        }
+    }
+
+    return C;
+}
+
+} // namespace detail
+
+
+/** operator*() for two matrices. */
+template<typename E1, class AT1, typename L1,
+         typename E2, class AT2, typename L2,
+         typename BO>
+inline typename et::MatrixPromote<
+    matrix<E1,AT1,BO,L1>, matrix<E2,AT2,BO,L2>
+>::temporary_type
+operator*(const matrix<E1,AT1,BO,L1>& left,
+          const matrix<E2,AT2,BO,L2>& right)
+{
+    return detail::mul(left,right);
+}
+
+/** operator*() for a matrix and a MatrixXpr. */
+template<typename E, class AT, typename BO, typename L, typename XprT>
+inline typename et::MatrixPromote<
+    matrix<E,AT,BO,L>, typename XprT::result_type
+>::temporary_type
+operator*(const matrix<E,AT,BO,L>& left,
+          const et::MatrixXpr<XprT>& right)
+{
+    /* Generate a temporary, and compute the right-hand expression: */
+    typedef typename et::MatrixXpr<XprT>::temporary_type expr_tmp;
+    expr_tmp tmp;
+    cml::et::detail::Resize(tmp,right.rows(),right.cols());
+    tmp = right;
+
+    return detail::mul(left,tmp);
+}
+
+/** operator*() for a MatrixXpr and a matrix. */
+template<typename XprT, typename E, class AT, typename BO, typename L>
+inline typename et::MatrixPromote<
+    typename XprT::result_type , matrix<E,AT,BO,L>
+>::temporary_type
+operator*(const et::MatrixXpr<XprT>& left,
+          const matrix<E,AT,BO,L>& right)
+{
+    /* Generate a temporary, and compute the left-hand expression: */
+    typedef typename et::MatrixXpr<XprT>::temporary_type expr_tmp;
+    expr_tmp tmp;
+    cml::et::detail::Resize(tmp,left.rows(),left.cols());
+    tmp = left;
+
+    return detail::mul(tmp,right);
+}
+
+/** operator*() for two MatrixXpr's. */
+template<typename XprT1, typename XprT2>
+inline typename et::MatrixPromote<
+    typename XprT1::result_type, typename XprT2::result_type
+>::temporary_type
+operator*(const et::MatrixXpr<XprT1>& left,
+          const et::MatrixXpr<XprT2>& right)
+{
+    /* Generate temporaries and compute expressions: */
+    typedef typename et::MatrixXpr<XprT1>::temporary_type left_tmp;
+    left_tmp ltmp;
+    cml::et::detail::Resize(ltmp,left.rows(),left.cols());
+    ltmp = left;
+
+    typedef typename et::MatrixXpr<XprT2>::temporary_type right_tmp;
+    right_tmp rtmp;
+    cml::et::detail::Resize(rtmp,right.rows(),right.cols());
+    rtmp = right;
+
+    return detail::mul(ltmp,rtmp);
+}
+
+} // namespace cml
+
+#endif
+
+// -------------------------------------------------------------------------
+// vim:ft=cpp