clifford_unit: fix possible bugs due to wrong operator[!=]= usage.

[ginac.git] / ginac / ex.cpp

diff --git a/ginac/ex.cpp b/ginac/ex.cpp
index f1835377d2fbd9b6e0e83c289feea3c8361e36ef..23a30833b5a436375918e34358a4208376cf00d6 100644 (file)
--- a/ginac/ex.cpp
+++ b/ginac/ex.cpp
@@ -3,7 +3,7 @@
  *  Implementation of GiNaC's light-weight expression handles. */
 
 /*
- *  GiNaC Copyright (C) 1999-2005 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2008 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -28,6 +28,7 @@
 #include "mul.h"
 #include "ncmul.h"
 #include "numeric.h"
+#include "matrix.h"
 #include "power.h"
 #include "lst.h"
 #include "relational.h"
@@ -254,6 +255,17 @@ bool ex::is_polynomial(const ex & vars) const
                return bp->is_polynomial(vars);
 }
 
+/** Check whether expression is zero or zero matrix. */
+bool ex::is_zero_matrix() const
+{
+       if (is_zero())
+               return  true;
+       else {
+               ex e = evalm();
+               return is_a<matrix>(e) && ex_to<matrix>(e).is_zero_matrix();
+       }
+}
+
 // private
 
 /** Make this ex writable (if more than one ex handle the same basic) by