code • words • emotions

Daniel Janus’s blog

Re-framing text-mode apps

5 February 2019

Intro

“But, you know, many explorers liked to go to places that are unusual. And, it’s only for the fun of it.” – Richard P. Feynman

A couple of nights ago, I hacked together a small Clojure program.

Continue reading

Happy Programmers’ Day!

13 September 2014

Happy Programmers’ Day, everyone!

A feast isn’t a feast, though, until it has a proper way of celebrating it. The Pi Day, for instance, has one: you eat a pie (preferably exactly at 1:59:26.535am), but I haven’t heard of any way of celebrating the Programmers’ Day, so I had to invent one. An obvious way would be to write a program, preferably a non-trivial one, but that requires time and dedication, which not everyone is able to readily spare.

Continue reading

You already use Lisp syntax

20 May 2014

Unix Developer: I’m not going to touch Lisp. It’s horrible!

Me: Why so?

UD: The syntax! This illegible prefix-RPN syntax that nobody else uses. And just look at all these parens!

Continue reading

DOS debugging quirk

6 April 2014

While hacking on Lithium, I’ve noticed an interesting thing. Here’s a sample DOS program in assembly (TASM syntax):

.model tiny
.code
  org 100h

N equ 2

start:
  mov bp,sp
  mov ax,100
  mov [bp-N],ax
  mov cx,[bp-N]
  cmp cx,ax
  jne wrong
  mov dx,offset msg
  jmp disp
wrong:
  mov dx,offset msg2
disp:
  mov ah,9
  int 21h
  mov ax,4c00h
  int 21h

msg db "ok$"
msg2 db "wrong$"
end start

Continue reading

2048: A close look at the source

2 April 2014

Dust has now mostly settled down on 2048. Yet, in all the deluge of variants and clones that has swept through Hacker News, little has been written about the experience of modifying the game. As I too have jumped on the 2048-modding bandwagon, it’s time to fill that gap, because, as we shall see, the code more than deserves a close look.

Continue reading

Lithium revisited: A 16-bit kernel (well, sort of) written in Clojure (well, sort of)

26 May 2013

Remember Lithium? The x86 assembler written in Clojure, and a simple stripes effect written in it? Well, here’s another take on that effect:

Continue reading

My top three iOS apps for mapping

13 September 2012

Living in London means that I now have a whole lot of new area to explore by cycling or walking. I try to take every opportunity to spend a free day or weekend out. One of the most important things when on the move is knowing where you are, where to go, and how to get there — and for that, you need a map. As I soon learned, the maps to use in the UK are the Ordnance Survey ones (either the Landranger/Explorer series, or maps by another publisher, such as AA, based on OS data). However, the Landranger series encompasses over 200 1:50000 maps, standing at some £8 each, and when that level of detail is not enough, there are more than 400 Explorer maps on top of that. Not only does this get pricey after a while, but also the sheer volume of map juggling quickly becomes impractical when you cycle a lot outside of town.

Continue reading

Lithium: an x86 assembler for Clojure

14 May 2012

Ah, the golden days of childhood’s hackage. Don’t you have fond memories of them?

I got my first PC when I was 10. It was a 486DX2/66 with 4 megs of RAM and a 170 meg HDD; it ran DOS and had lots of things installed on it, notably Turbo Pascal 6. I hacked a lot in it. These were pre-internet days when knowledge was hard to come by, especially for someone living in a small town in Poland; my main sources were the software I had (TP’s online help was of excellent quality), a couple of books, and a popular computing magazine that published articles on programming. From the latter, I learned how to program the VGA: how to enter mode 13h, draw pixels on screen, wait for vertical retrace, manipulate the palette and how to combine these things into neat effects. One of the very first thing I discovered was when you plot every pixel using sum of its coordinates modulo 40 as color, you get a nice-looking diagonal stripes effect. Because of the initially incomprehensible inline assembly snippets appearing all over the place, I eventually learned x86 assembly, too.

Continue reading

How to call a private function in Clojure

25 April 2012

tl;dr: Don’t do it. If you really have to, use (#'other-library/private-function args).


A private function in Clojure is one that has been defined using the defn- macro, or equivalently by setting the metadata key :private to true on the var that holds the function. It is normally not allowed in Clojure to call such functions from outside of the namespace where they have been defined. Trying to do so results in an IllegalStateException stating that the var is not public.

Continue reading

Lifehacking: How to get cheap home equipment using Clojure

12 April 2012

I’ve moved to London last September. Like many new Londoners, I have changed accommodation fairly quickly, being already after one removal and with another looming in a couple of months; my current flat was largely unfurnished when I moved in, so I had to buy some basic homeware. I didn’t want to invest much in it, since it’d be only for a few months. Luckily, it is not hard to do that cheaply: many people are moving out and getting rid of their stuff, so quite often you can search for the desired item on Gumtree and find there’s a cheap one a short bike ride away.

Continue reading