opaque data types (was: plist-based package.el (was Re: cl-defstruct-based package.el, now with ert tests and no external tar!))

[Ted Zlatanov <tzz@lifelogs.com>]

On Fri, 07 Jun 2013 12:07:44 +0900 "Stephen J. Turnbull" <stephen@xemacs.org> wrote: 

SJT> Aaahhhh, *hash* *tables*.  Now I like where you're headed!  An opaque
SJT> type, the modern programmer's heartthrob.  I have to agree with you
SJT> there.  "Opaque types are one honkin' great idea!  We should do more
SJT> of those."[1]

SJT> Footnotes: 
SJT> [1]  With apologies to Tim Peters.

I'd really like an opaque "password" type that doesn't print unless
retrieved with a special function, and is stored encrypted in memory.
Currently auth-source.el uses a closure for that, which is not ideal.
It's on my TODO list for some rainy day.

Generally, I love how Lisp balances readability, accessibility, and
power by limiting itself to data structures that are not opaque.  The
exceptions to that rule are the interesting edge cases :)

(By contrast, Java makes data structures and objects impenetrable by
default and requires nasty tricks to get introspection.  And on top of
that we have Guava, Scala, and Clojure... amazing!)

Ted