+static gboolean
+value_from_entry (gint col, GValue *val, gpointer data)
+{
+ GtkEntry *entry = data;
+ const gchar *text = gtk_entry_get_text (entry);
+ gdouble x = g_strtod (text, 0);
+
+ g_value_init (val, G_TYPE_DOUBLE);
+ g_value_set_double (val, x);
+
+ return TRUE;
+}
+
+
+/* Returns true, if there's text in the entry */
+static gboolean
+entry_not_empty (gpointer data)
+{
+ GtkEntry *entry = data;
+
+ const char *text = gtk_entry_get_text (entry);
+
+ return !g_str_equal (text, "");