F&O comments on string-join function

A few comments on the string-join function:

1. Should the second parameter have type string? instead of string*
(what would it do with multiple string values for the separator?)

2. It doesn't say what to do if second argument is empty sequence (if
indeed that should be allowed).

3. I think the last sentence should say "zero-length string" instead of
"empty string" to be consistent with the rest of the document, and
because it is clearer.  (There a few other places where "empty string"
has crept back in, too.)


Thanks,
Priscilla