beowulf

LISP 1.5 is to all Lisp dialects as Beowulf is to Emglish literature.

What this is

A work-in-progress towards an implementation of Lisp 1.5 in Clojure. The objective is to build a complete and accurate implementation of Lisp 1.5 as described in the manual, with, in so far as is possible, exactly the same bahaviour - except as documented below.

Status

Boots to REPL, but few functions yet available.

Architectural plan

Not everything documented in this section is yet built. It indicates the direction of travel and intended destination, not the current state.

resources/lisp1.5.lsp

The objective is to have within resources/lisp1.5.lsp, all those functions defined in the Lisp 1.5 Programmer's Manual which can be implemented in Lisp.

This means that, while Beowulf is hosted on Clojure, all that would be required to rehost Lisp 1.5 on a different platform would be to reimplement

bootstrap.clj
host.clj
read.clj

beowulf/boostrap.clj

This file is essentially Lisp as defined in Chapter 1 (pages 1-14) of the Lisp 1.5 Programmer's Manual; that is to say, a very simple Lisp language, which should, I believe, be sufficient in conjunction with the functions provided by beowulf.host, be sufficient to bootstrap the full Lisp 1.5 interpreter.

In addition it contains the function INTEROP, which allows host language functions to be called from Lisp.

beowulf/host.clj

This file provides Lisp 1.5 functions which can't be (or can't efficiently be) implemented in Lisp 1.5, which therefore need to be implemented in the host language, in this case Clojure.

beowulf/read.clj

This file provides the reader required for boostrapping. It's not a bad reader - it provides feedback on errors found in the input - but it isn't the real Lisp reader.

Intended deviations from the behaviour of the real Lisp reader are as follows:

It reads the meta-expression language MEXPR in addition to the symbolic expression language SEXPR, which I do not believe the Lisp 1.5 reader ever did;
It treats everything between a semi-colon and an end of line as a comment, as most modern Lisps do; but I do not believe Lisp 1.5 had this feature.

BUT WHY?!!?!

Because.

Because Lisp is the only computer language worth learning, and if a thing is worth learning, it's worth learning properly; which means going back to the beginning and trying to understand that.

Because there is, so far as I know, no working implementation of Lisp 1.5 for modern machines.

Because I'm barking mad, and this is therapy.

Installation

At present, clone the source and build it using

lein uberjar.

You will require to have Leiningen installed.

Usage

java -jar beowulf-0.1.0-standalone.jar

This will start a Lisp 1.5 read/eval/print loop (REPL).

To end a session, type quit at the command prompt.

Learning Lisp 1.5

The Lisp 1.5 Programmer's Manual is still in print, ISBN 13 978-0-262-13011-0; but it's also available online.

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