Re: hash-table-{to, from}-alist

[David De La Harpe Golden]

Stefan Monnier wrote:

> So the question is should we use #s(...) as CL does,

(That's definitely implementation-specific, just what clisp in 
particular does)

> or #s<...> as XEmacs does.

N.B. It's actually #s(...) in XEmacs too, at least when variable 
print-readably is t. Otherwise the not-readable #<...> (no "s") is used, 
as per Stephen J. Turnbull's posts to this thread, also shown in [1]

Since hashtables are typically used for largish numbers of keys, 
supporting such an XEmacs-like print-readably variable* and suppressing 
the output of key/value data (at least beyond a certain key count) for 
the non-readable #<...> case seems like it might be quite desirable, 
though I dunno if XEmacs actually does such suppression, CL
implementations tend to (regarding xemacs compat it can't matter much 
since it's only the non-readable case).

* itself similar to CL *print-readably*, though  there's no guarantee a 
particular CL implementation can actually print its hashtables readably 
no matter how you twiddle that. Clisp does its thing. SBCL spits out a 
#. read-time evaluation lump that constructs a hashtable. Clozure CL (at 
least the outdated version on my system) signals a print-not-readable 
error... [2]

[1] http://www.xemacs.org/Documentation/21.5/html/lispref_9.html#SEC67
[2] http://www.lispworks.com/documentation/HyperSpec/Body/v_pr_rda.htm