* lib/csv.rb: add Cell#to_str and Cell#to_s for /.../ =~ aCell,

"#{aCell}" and so on.

        * test/csv/test_csv.rb: add tests.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@5177 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/csv.rb

@@ -85,6 +85,20 @@ public
         @data == rhs.data
       end
     end
+
+    def to_str
+      content.to_str
+    end
+
+    def to_s
+      content.to_s
+    end
+
+  private
+
+    def content
+      @is_null ? nil : data
+    end
   end