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Re: [Scheme-reports] Seeking review of sets and hash tables proposals

On 05/24/2013 10:30 PM, John Cowan wrote:
> Per Bothner scripsit:
>> Note also some hash tables are sorted.  For example:
>>    http://docs.oracle.com/javase/7/docs/api/java/util/SortedMap.html
> That's an interface, and the classes that implement it are a tree map
> and a skip-list map, not a hash map.  AFAIK there is no way to be both
> ordered and have O(1) behavior.

You're right, of course.

A 'comparator' data type might be still be worth considering.
I could work well with a small library of utility routines.
For example (ascending PROJ) and (descending PROJ) take a one-argument
"projection" function that is applied to the elements to be
compared.  Another useful utility (useful for sorting)
takes a list of comparators, where the first element is
the primary key, the second the secondary key, etc.

Anyway, this is all very hand-wavy ...
	--Per Bothner
per@x   http://per.bothner.com/

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