Functional hashtables

[Christopher Lemmer Webber]

Hello hello,

I'm working on porting a library I've written from Racket to Guile.
Some interesting news on that soon.

In the meanwhile, I'm trying to figure out what to do about my need for
functional hashmaps in Guile.  Right now Guile ships with vlist and
vhash.  Andy also wrote fash.scm, which is what I've generally preferred
and used previously.

The reason I don't want to use vhashes is specifically this part of
vhashes in the Guile manual:

>   • It is _not_ thread-safe.  Although operations on vlists are all
>     “referentially transparent” (i.e., purely functional), adding
>     elements to a vlist with ‘vlist-cons’ mutates part of its internal
>     structure, which makes it non-thread-safe.  This could be fixed,
>     but it would slow down ‘vlist-cons’.

Oop!  That's a no-go for me.  But maybe there are other reasons to
prefer fash.scm too?

There's no separate package of guile-fash available anywhere, but it
would be easy enough to do if we're just using it with Guix.  It's
desirable to not have to keep copy-pasta'ing fash.scm around at least.

My time in Racket has convinced me that it's an extremely good idea to
have a well supported functional hashmap type in the language... extra
points if it's "first class" in syntax (my code has improved
considerably because of it; no more using alists where they'll bite you
later just because it "looks prettier").

Anyway, thoughts?

Nice to be back in Guile land!
 - Chris