Re: cannot compile: srfi-10 define-reader-ctor 'hash '#,(

[Panicz Maciej Godek]

2014-08-13 21:59 GMT+02:00 Jan Nieuwenhuizen <address@hidden>:
> Ludovic Courtès writes:
>
>> The problem is that SRFI-10 itself does not specify an external
>> representation for hash tables, nor does Guile.  Thus this patch cannot
>> be applied.
>
> Yes, I understand that...Still, "wouldn't it be nice" if Scheme/Guile
> had something that javascript has, in JSON hash tables are "simply"
>
>    {"key0": value, "key1": value}

I have been thinking about that issue a lot, and concluded that it
wouldn't be "the Scheme way".
Scheme already has a nice representation for associactions, namely the
assoc lists. However, they are a bit problematic, because they are
ordered by nature and hence there's not much one can do with their
linear access time.

The proper solution, I believe, is to provide some means to create
unordered collections (i.e. sets or multisets). Some hints for
constructing such collections were given by Daniel Friedman and
reminded recently (like 10 years ago ;]) in Guy Steele's talk for
Friedman's 60th birthday:
http://www.youtube.com/watch?v=IHP7P_HlcBk

After that, a paper came out which described that idea in greater detail:
http://projects.csail.mit.edu/wiki/pub/JoeNear/FernMonad/frons.pdf

Anyway, I think it would be nice to provide a notation for unordered
collections in Scheme, so that the associations, written as '{(key .
value) ...}, could eventually be optimized and perhaps implemented as
hash tables internally in some cases.