(And, at least now I have bumped Chomsky from the top of my blog.)
My friend and former colleague Adam Higgitt every Friday posts a list of “five things I have learned this week”. It’s popular and good fun – especially as Adam is not afraid of an argument if you challenge some of his claims.
For a while I tried to do the same thing myself, but failed miserably.
I am not going to try again, but I am proposing to try something different, if inspired by Adam.
So here is the first list of things “learnt this week” scientific or mathematical facts and amusements. I will aim for five, but this week just did not make it.
1. A random walk can be used to build a binomial distribution – but not a very good one!
Imagine a left-right ruled line centred on zero and a marker than can, in every time step move either left or right be one step where the probability of moving left and of moving right, are both the same: i.e., . At the “beginning of time” the marker stands at 0.
Then if we count the times the marker is at any given position they will be distributed bionomially (well, as we approach an infinite time). The BASIC code below (which I wrote using BINSIC) should give you an idea (this code runs the risk of an overflow though, of course and the most interesting thing about it is how unlike a binomial distribution the results can be).
10 DIM A(1001) 12 FOR I = 1 TO 1001 14 LET A(I) = 0 16 NEXT I 20 LET POS = 500 30 FOR I = 1 TO 50000 40 LET X = RND * 2 50 IF X > 1 THEN LET POS = POS + 1 ELSE LET POS = POS - 1 60 LET A(POS) = A(POS) + 1 70 NEXT I 80 PRINT "*****BINOMIAL DISTRIBUTION*****" 90 FOR I = 1 TO 1001 95 LET X = I - 500 110 PRINT X," ",A(I) 120 NEXT I
Up to this point I just had an informal “things that look different but are related through a reversible transformation” idea in my head. But that’s not fully correct.
A simple example might be the logarithms. Every real number has a unique logarithm.
Thirty-three years ago my brother and I got a new cassette player for Christmas.
That allowed us to write and save games for our ZX80 computer (like many ZX80 owners we found that an older cassette player just didn’t work) and in 1981 I wrote a Z80 machine code version of Conway’s Game of Life – still my proudest programming achievement.
Last year I sought to complete the circle by writing an interpreter/DSL that mimiced ZX80 BASIC and called it BINSIC as “BINSIC Is Not Sinclair Instruction Code” and then wrote a BASIC version of the Game of Life (see the screenshot below).
So, if you are from that generation computer users, or even if you are not, why not give it a try – more details here: BINSIC
- How to Digitize/Backup Cassette Tapes and Other Old Media (howtogeek.com)
- Useful Gadget of the Week: USB Audio Cassette Tape Converter Revives Old Memories (automatedhome.co.uk)
- “I built everything from first principles.” (metafilter.com)
- Brian Eno – Conway’s Game of Life (eoleary87.wordpress.com)
- Conway’s Game of Life in Racket (jeapostrophe.github.io)
Only slightly miffed that no one seems to have noticed that I was running BASIC on this platform more than three months ago 🙂
It would not be right or proper for me to intervene to stop this, but if you have been a BINSIC user then a proper third-party reference to it (followed by a clearance of the deletion message in the prescribed manner) would be very much appreciated.
The BINSIC article does not generate much traffic here (perhaps a visit a day), so I admit it is not a particularly important project in the world of computer science, but I hope it has been fun for at least a few people and it is worth keeping as a link to a quick and easy way to get BASIC on your computer.
- Wickedpedia: The dark side of Wikipedia (zdnet.com)
- Is Wikipedia going commercial? (salon.com)
- Another time. Another attack to Wikipedia. (jacopobacchi.wordpress.com)
- Wikipedia Is Nearing Completion, in a Sense (theatlantic.com)
- Where Are All the Women of Wikipedia? [Wikipedia] (jezebel.com)
- Requesting open-licensed, open-format recordings of the voices of Wikipedia subjects for Wikimedia Commons (pigsonthewing.org.uk)
Conway’s Game of Life has long fascinated me. Thirty years ago I wrote some Z80 machine code to run it on a Sinclair ZX80 and when I wrote BINSIC, my reimplentation of Sinclair ZX81 BASIC, Life was the obvious choice for a demonstration piece of BASIC (and I had to rewrite it from scratch when I discovered that the version in Basic Computer Games was banjaxed).
But Life is much more than a game – it continues to be the foundation of ongoing research into computability and geometry – as the linked article in the New Scientist reports.
For me, it’s just fun though. When I wrote my first version of it back in 1981 I merely used the rubric in Basic Computer Games – there was no description of gliders or any of the other fascinating patterns that the game throws up – so in a sense I “discovered” them independently, with all the excitement that implies: it is certainly possible to spend hours typing in patterns to see what results they produce and to keep coming back for more.
- “Life.bas” should run on any system that will support the Java SDK – for instance it will run on a Raspberry Pi – follow the instructions on the BINSIC page. A more up to date version may be available in the Github repository at any given time (for instance, at the time of writing, the version in Git supports graphics plotting, the version in the JAR file on the server only supports text plotting). On the other hand, at any given time the version in Git may not work at all: thems the breaks. If you need assistance then just comment here or email me adrianmcmenamin at gmail.
- BINSIC plotting working (cartesianproduct.wordpress.com)
- Relive the ZX81 experience on your desktop (cartesianproduct.wordpress.com)
- A glider on an aperiodic cellular automaton exists! (aperiodical.com)
- Running BASIC on the Raspberry Pi (cartesianproduct.wordpress.com)
- Google Hides a “Game of Life” Easter Egg on the Search Page (news.softpedia.com)
At the risk of being attacked as an enemy of all that is good, I have to confess to being less than riveted by the Olympics, so far. So I have made far more productive use of my time in seeking to recreate the computing experience of 30 years ago – by working some more on BINSIC – Binsic Is Not Sinclair Instruction Code, my reimplementation of Sinclair ZX81 BASIC.
I have finally got
UNPLOT to work – not on the same screen as ordinary output, but on a separate graphics console.
It’s just in the Git repo now (at Github under mcmenaminadrian) but an executable JAR will follow shortly.
Haven’t had a chance to investigate what happens if I tweak the settings on the thing – possibly I might be able to speed execution up. Could be that Java and Groovy is just too much bloat, could be that BINSIC just demands a lot of computation (I refuse to consider that it might be poorly designed and executed).
- Raspbian Linux now available for Raspberry Pi: Up to 40 percent faster than Debian (liliputing.com)
- Raspberry Pi now available for general order (slashgear.com)
- Raspbian: The fastest operating system for the Raspberry Pi (liliputing.com)
- Want to buy more than one Raspberry Pi? Now you can! (raspberrypi.org)
- ODROID-X: The $129 Quad-core Alternative to Raspberry Pi (tomshardware.com)
- Raspberry Pi launched by balloon broadcast images from 40km high (raspberrypi.org)
Here’s another BASIC “game” (it’s amazing that this sort of thing used to fascinate those of us with these machines), for you to try – it was fixing this up that helped me find the bugs:
10 REM **DICE GAME**SLR/1983** 20 LET A=0 30 LET B=0 40 PRINT "DICE GAME" 60 PRINT "YOUR THROW=" 70 GOSUB 160 80 PRINT "MY THROW=" 90 GOSUB 220 100 IF A>B THEN PRINT "YOU WIN" 110 IF A<B THEN PRINT "I WIN" 120 IF A = B THEN PRINT "TIE" 130 LET X$ = INKEY$ 132 IF X$ = "" THEN GOTO 130 136 CLS 140 IF X$ = "S" THEN STOP 150 GOTO 10 160 FOR G=1 TO 2 170 LET Z=INT (RND*6+1) 180 LET A=A+Z 190 GOSUB 280 195 PRINT 200 NEXT G 210 RETURN 220 FOR G=1 TO 2 230 LET Z=INT (RND*6+1) 240 LET B=B+Z 250 GOSUB 280 260 NEXT G 270 RETURN 280 REM Draw 282 PAUSE 100 285 IF Z = 1 THEN GOSUB 500 290 IF Z = 2 THEN GOSUB 600 300 IF Z = 3 THEN GOSUB 700 310 IF Z = 4 THEN GOSUB 800 320 IF Z = 5 THEN GOSUB 900 330 IF Z = 6 THEN GOSUB 1000 340 RETURN 400 PRINT "[ ][ ][ ]" 410 RETURN 420 PRINT "[*][ ][*]" 430 RETURN 440 PRINT "[ ][*][ ]" 450 RETURN 460 PRINT "[*][ ][ ]" 470 RETURN 480 PRINT "[ ][ ][*]" 490 RETURN 500 REM 1 510 GOSUB 400 520 GOSUB 440 530 GOSUB 400 540 RETURN 600 REM 2 610 GOSUB 460 620 GOSUB 400 630 GOSUB 480 640 RETURN 700 REM 3 710 GOSUB 460 720 GOSUB 440 730 GOSUB 480 740 RETURN 800 REM 4 810 GOSUB 420 820 GOSUB 400 830 GOSUB 420 840 RETURN 900 REM 5 910 GOSUB 420 920 GOSUB 440 930 GOSUB 420 940 RETURN 1000 REM 6 1010 GOSUB 420 1020 GOSUB 420 1030 GOSUB 420 1040 RETURN
The original game can be found here: http://zx81.reids4fun.com/zx81/dice/dice_list.html – I had to change it to cope with the main weakness of BINSIC – that GOTOs to lines inside loops fail.