> Maybe I missed it, but one relevant thing I did not see mentioned in this
> discussion is the fact that if a value x is rebound, and the type of the
> new x differs from that of the old, then some values whose implementation
> (definition) depend on x may become ill-typed.
> 
> -- 
> Frank Atanassow, Dept. of Computer Science, Utrecht University
> Padualaan 14, PO Box 80.089, 3508 TB Utrecht, Netherlands
> Tel +31 (030) 253-1012, Fax +31 (030) 251-3791

Thank you for the precision, but I took it for ganted that the type
(scheme) assigned by the type-checker to the new identifier was
compatible with the (rebound) identifier's type scheme (more precisely
if x has type scheme sigma and you redefine x with type scheme sigma',
then sigma' must be more general than sigma). Otherwise the idea of
redefinition is pointless since any thing can occur after a
redefinition and the language becomes unsafe.

Best regards,

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://cristal.inria.fr/~weis/