[R] reading lisp file in R

[Peter Crowther]

That's a nice example of why Lisp is both powerful and terrifying - you're
looking at a Lisp *program*, not just Lisp *data*, as Lisp makes no
distinction between the two.  You just read 'em in.

The two definitions at the bottom are function definitions.  The top one
defines the def-instance function.  Reading that indicates that it accepts
an atom as a name and a list of key-value or key-range-value lists as
properties, where they keys may be repeated to give you multi-valued
attributes in your result.  The bottom one defines a function for removing
duplicate entries of the same location.

The rest of the file (apart from the included email headers) is a whole
load of calls to the def-instance function.  In Lisp, you'd define the
functions, then just run the rest of the file.

To my knowledge, there is no generic way to read Lisp "data" into anything
else, because of this quirk that data can look like anything.  If anyone
can correct me on that, great, but I'd be somewhat surprised.  Therefore,
as David intimated, the tools you need are generic tools for handling text,
and you'll have to deal with the formatting yourself.  If I were doing a
one-off transform of this file, I'd probably reach for vi... but I'm an old
Unix hacker.  I certainly wouldn't teach that tooling.  awk or perl could
certainly handle it; or if you want to give students a wider view of the
world you might wish to try ANTLR and get them to write a grammar to parse
the file.  The Clojure grammar (
https://github.com/antlr/grammars-v4/blob/master/clojure/Clojure.g4) would
be an interesting place to start, although Terence Parr's comment of "match
a bunch of crap in parentheses" would probably give a flavour of what to
implement.  Depends what else the students are learning.

Hope this helps rather than hinders.

- Peter

On 18 January 2018 at 05:25, Ranjan Maitra <maitra at email.com> wrote:

> Thanks! I am trying to use it in R. (Actually, I try to give my students
> experiences with different kinds of files and I was wondering if there were
> tools available for such kinds of files. I don't know Lisp so I do not
> actually know what the lines towards the bottom of the file mean.(
>
> Many thanks for your response!
>
> Best wishes,
> Ranjan
>
> On Wed, 17 Jan 2018 20:59:48 -0800 David Winsemius <dwinsemius at comcast.net>
> wrote:
>
> >
> > > On Jan 17, 2018, at 8:22 PM, Ranjan Maitra <maitra at email.com> wrote:
> > >
> > > Dear friends,
> > >
> > > Is there a way to read data files written in lisp into R?
> > >
> > > Here is the file: https://archive.ics.uci.edu/
> ml/machine-learning-databases/university/university.data
> > >
> > > I would like to read it into R. Any suggestions?
> >
> > It's just a text file. What difficulties are you having?
> > >
> > >
> > > Thanks very much in advance for pointers on this and best wishes,
> > > Ranjan
> > >
> > > --
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> > David Winsemius
> > Alameda, CA, USA
> >
> > 'Any technology distinguishable from magic is insufficiently advanced.'
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