Re: LAST^2 CALL for SRFI 113, Sets and Bags

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To: John Cowan <cowan@xxxxxxxxxxxxxxxx>

Subject: Re: LAST^2 CALL for SRFI 113, Sets and Bags

From: Alex Shinn <alexshinn@xxxxxxxxx>

Date: Tue, 26 Aug 2014 15:49:22 +0900

Cc: srfi-113@xxxxxxxxxxxxxxxxx

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On Sat, Aug 23, 2014 at 11:59 AM, John Cowan <cowan@xxxxxxxxxxxxxxxx> wrote:

In cooperation with Kevin Wortman, I've added set-cartesian-product
and set-power-set to the SRFI and the implementation, along with their
bag-* equivalents.

This sounds like last minute feature creep better

left to another SRFI, possibly with another approach

entirely.

Specifically I think because of the combinatorial

explosion in memory needed, such operations are

better served by a generating API than one which

returns a complete data structure, either as an

abstract generator or as a loop syntax extension.

Such an API should also include combinations and

permutations, as in Gauche's util.combinations[1]

library. See TAoCP Vol. 4a 7.2.1 for algorithms.

[1] http://practical-scheme.net/gauche/man/gauche-refe_199.html

Alex