Game of Life in Postscript

smashr writes "It never really occured to me that postscript could be used for something other than printing, until I came across this page. Evidently someone has written the classic 'Game of life' entirely in postscript. You can even send it to the printer and have it output every single iteration.. now that would be a fun prank."

Comments

wow

[Kipper the Llama]

Sad memories of being a nine year old loser are flooding my brain at the mere mention of "The Game of Life".

Wow.

[JanusFury]

I find it impressive that a technology that's been around since 1985 is not only still usable, but it's used almost everywhere for printing and is also an extremely powerful language. If only more technology was created this way these days. Definitely a testament to the people who created postscript...

Re:Wow.

[g4dget]

PostScript survived because of its imaging model, which was far better than anything else around at the time. The PostScript language only survived because of the imaging model; the language itself has required numerous workarounds, add-ons, and conventions to make its continued use in printing practical, making it a complicated mess that still doesn't really work all that well as a language.

Adobe has pretty much admitted as much with their creation of PDF. Apple also dumped PostScript for PDF, for the same reasons.

PostScript was an idea worth trying, but a few decades later, we really know that procedural languages do not make good page description languages. The future belongs to standards like PDF and SVG.

Re:Wow.

[mark-t]

Definitely a testament to the people who created postscript

Person, actually. Postscript was invented by one man.

Postscript has an interesting story, actually. The man who invented it had, previously, designed the "language" to be used by Xerox's new laser printers. This was not a real programming language, but was simply a control language. Xerox was nevertheless entirely delighted with it, and paid him a fair amount of money for it. After he had finished this task for Xerox, he then decided to start from scratch and try to build a printer language that was more suited to his vision of what one should be. When he finished, he decided to notify Xerox of his new development (hoping, perhaps, to get another large paycheque from them), but Xerox declined to use it, wanting to stick with his first printer language that they were already beginning to use. He teamed up with someone else and founded the company Adobe, and they called the language "Postscript".

Webserver

[JohnFluxx]

Didn't someone write a webserver in postscript?

Anyway, most people know script it turing complete - this is hardly the greatest hack ever :)

But it's cool - i'm not being negative.

Re:Webserver

[Xonea]

Yes, it can be found here

It must be used with inetd though, because postscript doesn't support sockets...

OS

[spikexyz]

Ok, someone write an OS in it.

Much cooler PS hack

[ocelotbob]

PS-HTTPD - a webserver in PostScript.

Re:Duh

[Captain Lobotomy]

True. In fatc, it's a stack-oriented programming language (like Forth). When Apple released the original LaserWriter in the mid-80s, it was actually the most powerful *computer* they made at the time (next in line was the Mac Plus -- remember those?).

PostScript Fractals

[e271828]

If you like this sort of thing, check out the PostScript Fractals page. You can print out very detailed images from tiny PostScript files.

Go Game in 5 lines of PostScript

[_dl_]

%!PS-Adobe-1.0 EPSF-10. % PS GoBan (c) 1996 by Laurent Demailly
%%BoundingBox: 0 0 150 150 % *** http://www.demailly.com/~dl/go/ ***
/D{def} def/d{dup}D/e{exch}D/s{stroke}D/l{lineto}D/M{mul}D /f{fill}D/S{setgray}D
/R{grestore}D/m{moveto}D/z 9 D/c 15 D/x z c M D/p{42 sub d z mod 1 add e z idiv
1 add gsave 1 index c M 1 index c M c .5 M 1 0 arc gsave f R .5 S s c M e c M e
c .3 M 270 360 arc s R}D 0 0 x 2 M 1 0 arc .9 .7 .5 setrgbcolor f s 0 S c c x{d
c m d x l d c e m x e l}for s(BeJR\\IHP>=6U){p}forall 1 S(?TS[QcGZFOC){p}forall

PS-HTTPD

[SweetAndSourJesus]

I've never used it, but you're talking about PS-HTTPD.

Pretty cool, eh?

Ray Tracer

[CaseyB]

How about a PostScript ray tracer?

Re:Duh

[Cyberdyne]

Postscript is a programming language - so you can 'program' in it... whatever you want. Even something like the game of life. Crazy huh? That's technology for you.

Since it's Turing-complete, technically you could port an x86 emulator to it, and boot Windows in Postscript. In practice, of course, it would be insanely slow, but on a fast enough machine you could play Doom or Quake. 60ppm printer -> 1 fps ;-)

Postscript isn't just used for printers, either. NeXT used Display Postscript for the GUI, so applications were truly WYSIWG: the printer and the screen were rendering precisely the same source! Apparently this was one of the NeXT features which was inherited by Mac OS X, in modified form: parts of the GUI use Display PDF in much the same way.

stupid postscript tricks

[Anonymous Coward]

My own personal contribution to the world of stupid postscript tricks wasn't nearly as productive as this one. But I promise you it was funnier!

I wrote a program that substitutes occurances of one string with another one. You send it to the printer than laugh as everyone else's pages mysteriously have the word "this" replaced with "that". One time I loaded it on just before a friend printed his source code. He couldn't figure out for the life of him where his semicolons had gone! Ah... youth.

The best part is, the code stays resident until the printer is power cycled. This enables slightly more sinster uses for this sort of thing. One of my professors used to joke about using as program like this to change the numbers on his paycheck when it was being printed!

The code is still on my website near the bottom. It's called PSReplace.

Re:So why is this a good thing?

[WolfWithoutAClause]

It's not exactly a scripting language. It's actually a very close cousin of 'forth'. It runs quite quickly, and doesn't particularly excel at text processing, which most scripting languages do.

As other people have pointed out, it's useful to have a fairly powerful language in a printer since it allows the printer to adapt the printed stuff to the paper size and so forth (no pun intended).

Another language that is very closely related is pdf; as I understand it, it's pretty much postscript with a few cludges on the side to make it run faster.

Re:So why is this a good thing?

[Matthias Wiesmann]

Shouldn't the actual processing of data be solely handled by the computer? I mean, this article clearly says that it can tie up the printer for a long time if you actually try this.

The main advantage of postscript is that it is versatile. Of course coding games or fractals is extreme, but there are many other uses:

• You can send the graphical data in a very compact form, vectors and compressed bitmaps (the Apple drivers could compress bitmaps in JPEG and would transmit a JPEG decompresser postscript program).
• You can transmit your own data format. Instead of transforming your data into "real" postscript, you send a set of postscript procedures that reproduce the behaviour of your graphic language. This was actually one of the primary requirements of postscript, something that could handle quickdraw (Apple's graphic language pre OS-X) reasonably well. DVI2PS does a similar trick.
• You can factorise out common data. For instance you could transmit a form once, and then only send the data to fill out multiple versions of the form.
• Pre-loading - you can upload common fonts to the printer, this saves you the time of including them in all jobs. Some high-end postscript printer even have hard drives to store those fonts.
• Precision handling - instead of calculating word justification on the computer, you send a procedure to calculate word positioning to the printer, this ensures that justification is done using the printer's font metrics and knowing the printer's resolution.
• Special handling and configuration. Special printer configuraton can be handled using postscript. For instance on certain printers, the user has to enter a PIN to trigger output. This is very usefull for sending sensitive documents to shared printers.
• On the fly reconfiguration - for instance you can reprogram the printer to do 2-up or 4-up printing quite easily.

This design made a lot of sense when postscript printers started, bandwidth to the printer was bad (serial, parrallel or localtalk) and processing power on the machines was low - in fact it was common to have a laserwriter II (68020) attached to a classic 9' macintosh (68000).

Even nowadays this design makes sense for network attached shared printers - this ensures that page composition is not tied to the client machines. Also you have to realise the bitmap of printing page is quite large: an uncompressed A4 page 300 DPI black/white bitmap is around 15MB. Today's laser printer support 2400 DPI, that means nearly a Gigabyte per page.

Easy to view postscript files

[mnemonic_]

Install Ghostscript first, then use GSView to open the .ps files.

Xerox, Copiers with SmallTalk via GhostScript

[jerryasher]

By the mid-90s, Xerox had written what was basically a SmallTalk interpreter using GhostScript. It was called DocuScript.

With that, Xerox wrote all sorts of applications for hallway copiers, including web browsers, hang-man games, and image processing/manipulation applications.

Take a piece of paper with an image you want to copy. Circle the image. Scan it. Take a piece of paper that you want the image on. Mark where the image goes. Scan the paper. Output: new piece of paper with the image from the first on it and the other elements from the second piece.

Ooops, you dropped 200 pages of a paper on the floor, and you have gathered it up in the wrong order. Circle the page number on the first page of the paper. Scan the entire paper in. Output: your paper now resorted according page number.

Go to a hospital and triage yourself by taking a printed image of the human body and circling on the image where you hurt and scanning it in to the hallway copier.

Take your 100 page paper and scan it into the hallway copier. Get a one page token in return (containing, basically, an encoded URL) Fly across country to a conference holding only that one page token. At the conference scan in your token. Output your 100 page paper.

And then, being Xerox, they found they couldn't/wouldn't/didn't want to sell it. Talk about the Game of Life!

Re:Xerox, Copiers with SmallTalk via GhostScript

[leighklotz]

>And then, being Xerox, they found they couldn't/wouldn't/didn't want to sell it.

Actually, Xerox did sell it, in Japan, as the DocuStation IM 200. When Java came out, we and otehrs worked with Sun to add the image processing features that were necessary (which became java2d) it was re-written in Java and sold again as FlowPort, and is still sold.

At the time the choice was made, we were examining Scheme, but felt a lot of resistance from the industrial engineering community we were targeting. So, although I helped develop 6.001 and the book "Structure and Interpretation of Computer Programs" that introduced Scheme, we abandoned that approach and looked for a language that would be more palatable to the printer and copier engineers. The system was written in PostScript because it was an interpreted language that was capable of running inside hardware such as copies, scanners, and printers. There were hired industry pundits who had suggested that we use Visual Basic, but that was even harder to fit into a copier in 1991, so PostScript it was.

Just as we were making the decision, I saw on alt.sources a new small object-oriented language announced and tried it out, but it had absolutely no class libraries, and no tools, and nobody had hever heard about it before (some guy named Guido) so we passed up on Python...

The goal was to make paper be the universal access portal to information, and to piggyback on images as the universal information transfer medium. We did hyperlinks on paper, used dialup modems for transferring information, etc. Basically it was the web and web forms on paper. Now the focus is on capturing paper documents and their metadata and making them first-class citizens in the office network.

The DocuScript language was actually much more like Java than like Smalltalk. It did have an object-oriented database, which Java lacks, but consider the following:

• Much of the PostScript code was written in PdB, a C++-like language compiled to PostScript. PdB was written at The Turing Institute by Arthur van Hoff, who later went on to write the first Java compiler, with a remarkably similar syntax. So, the system was written in a precursor to Java with GS as the virtual machine.
• Herb Jellinek worked on the "configurable desktop universal browser" part of the project at PARC. He left and went to Sun to work on Oak and in the meantime, WWW happened and became the protocol for the "universal browser", and he wrote HotJava, which was the web browser that kicked off the Java revolution.

• The Paper User Interface forms were all done as small PostScript programs that, depending on which set of definitions was loaded into the environment, either rendered a printable image to the image buffer, or read the scanned image from the image buffer and read the checkboxes. The layout decisions were all done with PostScript routines.

  So, in that sense, the layout was like LaTex, where the formatting commands are actually short programs or macros that bottom out into an implementation of primitive operations. After the product was launched, Larry Masinter of PARC convinced me that the LaTex-programmmatic approach was wrong, and that we needed to use a static description language, a path I had resisted because there were no good ones. But in the interim, again WWW had hit, and HTML seemed good. We did a Paper User Interface version of the WWW (now going full circle from our original idea of paper access to information to paper being a proexy for access to information via the WWW) and we made a tool to print Paper UI on any web page.

  Initially we did this as well in PostScript, but found that we needed something faster for the HTML parsing and layout, so we got a company called Universal Access to do that for us. They had a tool they were developing, and they prototyped it for us, and their other customer was a company called Unwired Planet that wanted to make a transcoder to convert HT

yes, and...

[pb]

Conway's Game of Life is also turing complete; therefore, you can regard this PostScript hack as proof that PostScript is turing complete as well, since you could implement a turing machine on top of Life, on top of PostScript..... :)

Re:Please forgive me

[pohl]

...is anyone concerned about the image of the tech community and finding more realistic ways to demonstrate the creativity and resourcefulness of nerds?

I once spent a day with a guitarist of immense talent. He spent countless hours with his instrument, but not making music...it was all just pointless scales, arpeggios, chord progressions around the cycle of fifths...not one bit of actual music did he perform. Sure, it was amazing to watch, but I couldn't understand why he was wasting his immense muscial intellect with such mundane exercises.

I wonder where he got the talent. Must have been a gift from god. It surely couldn't be that tireless practice of one's art leads to mastery, and that anything that helps one make practice fun aids in one's journey towards eminence in one's field...nope, no way.

Thinking in PostScript

[c]

The best source about PostScript as a programming language is book "Thinking in PostScript" (http://www.rightbrain.com/pages/books.html).

I read it originally to learn PostScript from a printing perspective, which was somewhat futile. Very little of the book actually talks about printing or page layout at all.

Anyhow, a quick read of the table of contents would be enough to understand that the Game of Life in PostScript is neither difficult nor terribly interesting.

c.