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Re: Raising awareness about guile-pfds status

From: Linus Björnstam
Subject: Re: Raising awareness about guile-pfds status
Date: Tue, 16 Jul 2019 09:07:21 +0200
User-agent: Cyrus-JMAP/3.1.6-731-g19d3b16-fmstable-20190627v1

On Mon, 15 Jul 2019, at 23:19, John Cowan wrote:
> On Mon, Jul 15, 2019 at 4:50 PM Linus Björnstam 
> <address@hidden> wrote:
> > If it is HAMTs or persistent vectors you want, I have a git repo of Andy's 
> > Fash and Fector (functional hashmaps and functional.vectors). Fash lacks 
> > some parts to become a fast implementation of (srfi 146 hash), 
> Is there a speed problem with the sample implementation of (srfi 146 
> hash)? It's a HAMT package written by Art Gleckler.

I didn't mean to sound like I was criticizing Arthur's implementation. What I 
meant was that fash currently lacks a fast way to delete keys. I could add a 
<fash-null> value and set a deleted value to that, but I would like to do it 

Fash and Fector also does some things differently from the other HAMTs/pvectors 
I tried (note I did not try the reference implementation) that runs fast in 

> Note that fectors are a bit specialized: they are very fast for both 
> ref and set if you don't change the "current branch" very often, but 
> slower if you do. Ordinary tree functional vectors have the same big-O 
> no matter what. There will be a fector SRFI.

Compared to Bagwell's VLists pvectors/fectors are generally slower, but adds 
the ability to set arbitrary values. I have been playing with the idea to 
create a fast, thread safe VList library with support for transients as I 
suspect it would be a slightly less capable, but much faster, alternative to 
fectors. Andy's fectors are actually faster than guiles VLists for everything 
except random access, but making the VLists support transients (and a way to 
iterate without using indexes) would change that.

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