[plt-scheme] Immutable mappings on symbols

From: Carl Eastlund (carl.eastlund at gmail.com)
Date: Thu Jan 13 14:06:47 EST 2005

MzScheme provides mutable hash tables keyed by symbols - actually, by
any data - but I can't find any functional mappings, i.e. where insert
and remove operations produce new mappings and preserve their inputs. 
I've had many occasions to want lookups based on symbols and it would
be nice to have the option of persistent data.  Is this present
somewhere I've overlooked, or is this a feature that could be added?


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