Nils M Holm's Ephemeralia
Who am I? |
No, really! |
What's new? |
CS and Math |
Retro Computing |
Odds & Ends |
Books I've Written
Computer Science and Math
- LISP From Nothing
- This text plays with the theme of minimal LISP by providing several
implementations from a simple metacircular evaluator to a full compiler
that emits a single, self-contained C program. The discussion is embedded
in reflections on what hacking looked like in the early days of LISP.
All source code from the book is in the public domain.
- LISP System Implementation
- A rather massive volume about the design and implementation of an
interactive LISP environment in C and LISP. Focusing on compilation to
abstract machine code, but covers all aspects of LISP implementation,
including garbage collection, syntax analysis, code generation, semantics,
tail call elimination, non-local exits, error handling, I/O, image
files, and much, much more... The
source code contained in the book
is in the public domain.
- Write Your Own Compiler
- The tiniest compiler book I have ever written. It covers
all steps in the compilation process from high level language
(T3X) to executable (ELF). Lots of diagrams, lots of code, zero
theory. The tour through the compiler itself spans less than 100
pages. All code in the book is provided under the CC0 license
(public domain). It can be downloaded below.
- An Introduction to Array Programming in
- This book introduces you to the world of solving problems with
array operators, adverbs, idioms, and functions.
Using examples of varying complexity, from a mundane matrix
formatter to a complete Gaussian elimination solver, it takes
you on an entertaining tour through the
- Practical Compiler Construction
- This book offers a tour through the full compiler for a clean and sane
subset of the C programming language (C89), covering lexical analysis,
parsing, semantics, code generation, optimization, and runtime support,
including lots of clarifying annotations and diagrams. The SubC compiler
discussed in the book is in the public domain and can be downloaded
- Prolog Control in Six Slides
- The design and implementation of a pure PROLOG interpreter plus
cuts in R4RS Scheme, based on a set of slides explaining the control
algorithm behind depth-first resolution with negation as failure
- Scheme 9 from Empty Space
(get the interpreter,
play the game)
- S9fES is both a book and an interpreter for the R4RS
programming language. The book offers a guided tour through every single
line of the interpreter with lots of annotations and diagrams. It covers
even the gory details, such as macro expansion,
and tail-call elimination.
- An Introduction to Statistics with
- An introduction to the statistics library of the
Klong programming language, covering
data representation, visualization, basic statistical functions,
probability distributions, χ2 tests, and linear and
- NMH's Incomplete Dictionary of
- A dictionary of statistics and probability that focuses on
application and comprehensibility rather than completeness, hence
an incomplete dictionary. Topics covered include probability,
inference, modelling, regression, hypothesis testing. Contains lots
of beautiful illustrations. All pages freely available, so you can
take your own sample.
- Compiling Lambda Calculus
- An introduction to lambda calculus and the compilation of functional
languages. Covers reduction, convertiblity, fixed points, representation
of closures, and compilation of Scheme to C. The text is completely
self-contained, but basic understanding of formal logic and programming
will be helpful. Code is in Scheme und provided under the CC0 license.
- Statistics, a short and painless
- A small book that covers the most fundamental principles of
probability and statistics in simple and straight-forward prose, but
without dumbing it down. Intended for students of natural and social
sciences as well as everybody else who always wanted to know how
- Sketchy Scheme, 4.5th Edition
- A beginner-friendly introduction to functional programming in Scheme.
This is a step-by-step guide to problem-solving in the functional way.
The book contains lots of example, from trivial to advanced, as well as
Scheme definitions of many standard procedures, an informal explanation of
continuations, and a digression dealing with lambda calculus.
- Logic Programming in Scheme
- An introduction to the principles of logic programming in MicroKANREN,
covering predicates, goals, negation, cutting, and the translation of
functional code into declarative code. Chapter two uses logic programming
to solve the well-known Zebra puzzle, and chapter three contains the
complete and annotated implementation of MicroKANREN in portable Scheme.
- Scheme 9 from Empty Space
(get the book,
play the game)
- S9fES is both a book and an interpreter for the R4RS
programming language. The interpreter is a very mature, portable and
easily extendable implementation of the language. It provides an
interface to some common Unix system calls, a large library, and compiles
natively on Plan 9.
- LISP9, an experimental LISP system
- A LISP system that is intended to be hackable and comprehensible.
The language is a cross between R4RS Scheme and ancient LISP with
terse keywords, low-level macros, and simple semantics. The
implementation is in C and LISP9. There is a comprehensive
book describing the implementation.
- Klong, a simple array language
- Klong is an array language, like K or APL. Its programs use
operators to manipulate lists (vectors) and (multi-dimensional)
arrays. Klong is a mathematical notation rather than a programming
language. It uses the ASCII alphabet and has simpler semantics than K.
Its interpreter is based on S9core and
should run on all systems providing a C89 compiler as well as on
- Kilo LISP, a kilo byte-sized LISP
- Kilo LISP is a purely symbolic LISP system that runs in
64 kilo bytes of memory (hence its name). It is written in C89
and compiles fine using SubC (below), Turbo C, or any modern C
compiler. The code is about 25K bytes of comprehensible C and LISP.
There is also a CP/M version and an
extended version for DOS and Unix.
- The SubC Compiler
- SubC is a clean, fast, and simple compiler for a subset of C89 that can
compile itself on various BSDs, Linux, Windows, and other systems. It also
cross-compiles to DOS. Its code is in the
- The T3X Compilers
- T3X is a small, portable, procedural, block-structured, recursive,
almost typeless, and to some degree object-oriented programming language.
It targets the Tcode machine, the 8086 under DOS, and the 386 and
Alpha processors under Unix.
- T3X9 is a tiny, block-structured,
procedural language. Its compiler can compile itself in the blink of
an eye (0.05s on a 750MHz notebook). It currently generates ELF
executables for FreeBSD-x86. T3X9 is a subset of T3X.
- The XT3X Compiler and Virtual Machine
- A T3X9 compiler and Tcode machine extended with functions for X11
graphics and OSS sound. Intended for writing simple video games as they
were ubiquituos in the 1970's and 80's.
- mLite, a lightweight, dynamic functional
- mLite is a general-purpose, functional, lightweight, dynamic
programming language. It borrows ideas from both the Scheme and
Standard ML languages, taking most of its syntax from ML and its
dynamic nature from Scheme. It extends ML-style pattern matching by
adding guarded patterns and also introduces the principle of
- CP/NC – A Control Program for the NC100
- CP/NC is a CP/M-compatible operating system for the Amstrad NC100
Notepad Computer. It is based on Russell Marks's ZCN operating system,
but aims to feel more like an old-fashioned CP/M system.
- –––==[The DOS Vault]==–––
- Some DOS programs from the 1980's and 1990's, most of them written
by me, quite a few of them never published before. Includes a few games,
the T3X compiler, a small database program, etc.
- LISPy things you can do in 64K bytes of
- Some of the first machines that ran LISP had less than 64K bytes
of memory, and yet there are lots of fun things that you can do on
such a machine. An exploration of purely symbolic LISP in limited
- VE, a visual editor for
- This is a small (20KB) editor for Z80-based CP/M machines.
It implements a subset of VI and is optimized for slow serial
lines. Requires a 4MHz CPU and a VT52 terminal. Also works on
the CP/NC console. Source code (in
- BTN11 is a two-pass assembler that generates absolute
binaries for various models of the PDP-11. It is written in
K&R (pre-ANSI) C.
- unproto 1.7
- This is a slightly modified version of
Venema's unproto program (also via
that works more cooperatively with the Mark Williams C compiler
on Coherent 3.x. Here are the essential
differences between the last
official version (1.6) and this one.
Odds & Ends
More or less random things that keep me busy.
- Science Fiction, Baby!
- A gallery of science fiction stuff that I have created in the past
- Raja Yoga Revisited
- A guide to systematic self-exploration based on ancient yoga
scriptures, like the Upanishads, the Bhagavad Gita, etc. An
attempt to view meditation in a scientific light. From 2009 but,
hey, the sources are much older! ;)
- Attention in the Digital Age
- How does the ubiquitous fight for attention form our habits?
A statistical analysis and opinionated essay based on data from
the web server logs of this site.
- Sensitivity as a Handicap
- A short essay explaining sensitivity, why high sensitivity is
a disadvantage in our society, and why this is a loss for all of us.
- Love, Impending Doom, and the Drake
- Why we are doomed as a civilization, and why this is both inevitable
and prefectly OK. An essay about a possible explanation of the Fermi
- What to do with a high IQ?
- Most people think that a high IQ will make you successful,
attractive, socially respected, etc, but many people actually
suffer from being highly intelligent. This paper investigates
the seeming paradox. Basic statistics required.
- Where Do The Failed 0.1% Go? (PDF)
- An article about two highly intelligent people who fell through
the social safety net. Including suggestions on how not to fail such
people in the future. Published in Vidya #324/325 in 2015. Erratum:
on the bottom of page 3, "window of 30 IQ points" should be
"window of 15 IQ points".
- Lambda Calculator
- A set of functions and a REPL for the λKβη-calculus,
providing normal-order and applicative-order reduction, tracing,
pretty-printing, various transformations, Church numerals, etc.
- Minimal quasiquote expander using syntax-rules
- Simple quasi-quotation in seven lines of Scheme, for
your enjoyment or as a quick-and-dirty solution for Schemes that have
syntax-rules, but not
There used to be a link to free PDF copies of some draft versions and
obsolete books here. The page is gone, but a copy can be found in the
- Lightweight Compiler Techniques
- A discussion of techniques for implementing simple yet efficient
compilers for procedural languages. Covers all phases of compilation:
scanning, parsing, optimization, code synthesis. Little theory, lots
of code. The T3X compiler described in this book can be found below.
- Zen-Style Programming
- An introduction to various aspects of computer science at break-neck
speed: functional programming, arbitrary-precision arithmetics,
meta-circular evaluation, searching and sorting, the limits of
computability, streams and generators, formal grammars, syntax
analysis, regular expressions, logic programming, design and
implementation of programming languages, and much more...
Code: Zen Lisp
- Die Anatomie einer Programmiersprache
An early precursor to Lightweight Compiler Techniques in German.
Code: BSL Compiler Kit
- FOOGOL IV, V5
- Lindberg's FOOGOL IV compiler hacked up to emit 386 assembly
language. Also converted to modern (ANSI 89) C. Compiles fine
- An interpreter and compiler for an obscure BASIC dialect that I
have created back in the early 1990's. Includes some simple games
as example programs. The compiler is written in MINBASIC.
- Mini Scheme v.3
- An extended but still tiny version of Moriwaki and Kida's
Mini Scheme interpreter, featuring string operations, type checking,
file operations, improved macro syntax, and more complete error
- PD Korn Shell
- A slightly patched version of pdksh, compiles on most modern
BSD's and has a clear-screen function that you can bind to
a key. This was the one tcsh feature I was missing most in pdksh.
And: yes, I actually use this shell. :)
- S9fES Interpreter, 2007 (1st ed.)
- The original version of the Scheme 9 interpreter from the
first edition of the book, including fixes to the errata from 2009.
- S9fES Interpreter, 2014 (3rd ed.)
- The Scheme 9 interpreter from the third edition of the book.
- S9fES Interpreter, 2018 version
- The last version of the original (pre-Reimagined) Scheme 9
- SOL Operating System
- SOL is a tiny, FORTH-based operating systems for the PDP-11
(sol-11.zip) and the IBM PC
There is also a generic
version (sol3.zip) running on a
virtual stack machine. You need BTN11 (above) to compile the
PDP-11 version. Bootstrapping the other versions requires a working
T3X compiler. Good luck!
- T3X Compiler, version 8.1.7b
- T3X is a lightweight procedural language with backends for the
8086 (EXE), 386, Alpha, and the Tcode Machine. It features modules,
objects, a full optimizing compiler, and a set of tools for
manipulating Tcode. The Tcode port of the 8.1.7b compiler works fine
on 64-bit systems. Development of T3X ceased in 2004.
Version 6.8 of the compiler is
described in the book "Lightweight Compiler Techniques" (above).
- An interpreter, compiler, and editor for a super-terse dialect of
FORTH. Brevity = expressiveness? You decide. Lots of funny sample