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M:N Dictionaries

This page is part of the web mail archives of SRFI 44 from before July 7th, 2015. The new archives for SRFI 44 contain all messages, not just those from before July 7th, 2015.



The last seemingly incomplete part of the spec seems to be the
Dictionary type, which specifies m:n mappings.  While the interface
currently specified by the SRFI would work, it has a couple of
weaknesses:

  * It doesn't distinguish between dicts where values mapped
    by a key must be unique (ie a dict-set) or not (dict-bag).

  * Few people I've spoken to (including myself) know what
    actually makes a good interface for such dictionaries.

The former point argues somewhat to *three* map types, and both
say to me that more work (possibly a lot more) would be required for
an interface that is worthy of being called Schemely.

However, I'm of the opinion that the m:1 Maps currently defined are
pretty non-controversial and elegant, so I'm considering dropping
Dictionaries from this SRFI, but having a fairly strongly worded future
work statement in the SRFI about them, and also archiving the current
API on this list.  This would leave SRFI-44 very usable for 99% of
people (who really just want a hashtable), but not accidentally
standardize an M:N interface which frankly needs more expertise than is
currently assembled.

        Scott

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