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Re: SRFI 121: Generators

This page is part of the web mail archives of SRFI 121 from before July 7th, 2015. The new archives for SRFI 121 contain all messages, not just those from before July 7th, 2015.

That's not the RnRS convention; cf. "abelian group".


> make-for-each-generator: obj may be any kind of "collection" but AFAICT
> that term doesn't have a precise meaning here.

No, it doesn't.

OK, so this should be explicitly defined somewhere right? A programmer needs to know what data types they may safely assume will work. I imagine that for the purposes of this SRFI, "collection" may be any of list, vector, bytevector, string, or generator.


> gmerge, gunion, gintersection: The description talks about order but is
> unclear on whether it means increasing or decreasing order. How about
> saying "elements in strict increasing order according to a SRFI 114
> comparator". The "strict" qualifier implies there are no duplicates in the
> input.

Increasing order, yes.  I see no reason to forbid duplicates particularly.

Well if a sequence has duplicates then it isn't really a mathematical set, and the conventional definition of set union, etc. does not work. It's then unclear whether these are actually multiset operations, where duplicates should be retained in the output; or whether they are set operations, and duplicates should be filtered out of input before performing the conventional set operations.

A less important consideration is that handling duplicates takes some effort, so these procedures can be faster if they are free to assume that inputs have no duplicates.