Trying to use a template class with ranges

[mark]

I forgot to mention: I want the class to work with:

Diff(aForwardRange, bForwardRange)
where T = ForwardRange, E = anything that supports ==
A common use case is for two sequences of strings (i.e., lines 
read from two files).

Diff(aString, bString) where
T = char[] or wchar[] or dchar[] E = char or wchar or dchar