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*To*: RRRS-Authors@mc.lcs.mit.edu*Subject*: Proposals for R4RS*From*: Pavel.pa@Xerox.COM*Date*: Wed, 27 Apr 88 17:47:33 PDT

1. It would be nice if R4RS provided the simplest possible support for a portable implementation of hash-tables. As far as I can tell, the only things required are two procedures: EQ-HASH object Returns an integer with the property that (EQ? a b) implies (= (EQ-HASH a) (EQ-HASH b)). Implementations are encouraged to make the converse true as well in as many cases as possible. EQV-HASH object Returns an integer with the property that (EQV? a b) implies (= (EQV-HASH a) (EQV-HASH b)). Implementations are encouraged to make the converse true as well in as many cases as possible. I think that with these as primitives, one can portably write the corresponding EQUAL-HASH procedure and essentially any other equivalence-relation hashing function. Thus, this appears to be sufficient for an efficient implementation of hashing, working in terms of normal vectors. Note that no ``unhash'' procedures are provided, so none of the difficulties that caused OBJECT-HASH and OBJECT-UNHASH to be removed exist here. 2. Is there any reason not to make ``.'' and ``{'' and ``}'' extended alphabetic characters? Dot, in particular, is useful for EXTEND-SYNTAX implementations or other things in that style. Perhaps someone could simply explain the criteria for inclusion in or exclusion from that extended alphabetic characters list? Comments?

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