John Cowan: 
> Alternatively (and most Schemely / Common Lisply in my view):  If you
> have a value, return it; if you don't have a value, return zero values.

Fair point.

One of my goals (not necessarily shared by everyone) is to have a notation and 
implementation that is easily ported to any Lisp-based languages.  It's not 
clear to me that all Lisp-based languages directly support performing and 
detecting no-value returns.  E.G., I haven't checked, but IIRC, ACL2 does not 
permit them.  That doesn't mean we *can't* do it, but if there's a clean 
alternative, I'd rather not.

In any case, I don't think we need them. Tecursing to t_expr is really simple, 
clean, and has the effect of retrying.  Then we don't need to return "no 
value"; we just keep trying until we get a value (and EOF is a value).

--- David A. Wheeler

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