Daniel Janus’s blog
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
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.
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:
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.
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.
How to call a private function in Clojure
25 April 2012
tl;dr: Don’t do it. If you really have to, use
A private function in Clojure is one that has been defined using the
defn- macro, or equivalently by setting the metadata key
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.
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.
Ever wanted to programmatically file a lawsuit? In Poland, you can.
21 March 2012
This has somehow escaped me: just over a year ago, the Sixth Civil Division of the Lublin-West Regional Court in Lublin, Poland, has opened its online branch. It serves the entire territory of Poland and is competent to recognize lawsuits concerning payment claims. There is basic information available in English. It has proven immensely popular, having processed about two million cases in its first year of operation.
Combining virtual sequences
or, Sequential Fun with Macros
or, How to Implement Clojure-Like Pseudo-Sequences with Poor Man’s Laziness in a Predominantly Imperative Language
9 December 2011
Sequences and iteration
There are a number of motivations for this post. One stems from my extensive exposure to Clojure over the past few years: this was, and still is, my primary programming language for everyday work. Soon, I realized that much of the power of Clojure comes from a sequence abstraction being one of its central concepts, and a standard library that contains many sequence-manipulating functions. It turns out that by combining them it is possible to solve a wide range of problems in a concise, high-level way. In contrast, it pays to think in terms of whole sequences, rather than individual elements.