Kris Howard: Okay. So, just so I know what I’m deal­ing with here, how many of you have ever knit­ted in your entire life? Oh sweet, like every­body. That’s real­ly good. If you’ve got them, and I know we do have knit­ters in the audi­ence, please feel free to whip it out, knit along— [indis­tinct; mic issue] Feel free to knit through the talk. I love that. 

As for the rest of you mug­gles[laugh­ter] Don’t wor­ry, no pri­or expe­ri­ence is assumed, and I’m not going to teach you either. I’m here to talk about code, after all. So my goal is to con­vince you that this

…is actu­al­ly more sim­i­lar to this

…than most peo­ple realize. 

Because real­ly when it comes down to it, this is actu­al­ly this: 

And to com­put­er pro­gram­mers, that looks a hell of a lot like com­put­er code. And you don’t need take my word for it. I’m sure some of you saw a month ago some engi­neer at Uber tweet­ed this

…and it went viral, and every­body like sent it to me. Because even though I’ve been say­ing it for years when like a dude says it sud­den­ly it’s novel. 

But snark­i­ness aside I’ll intro­duce myself. So, I’ve been work­ing in tech a hell of a lot longer than I’ve been a devel­op­er. I’m sor­ry. A hell of a lot longer than I’ve been a knit­ter. So tech first. I grew up in the US, and I worked in London for a while before I moved to Australia in 2001. And when I got here I had to wait a while for my work visa to be approved. And, young per­son, we did­n’t have Netflix back then. 

So I decid­ed to learn a hob­by. And I thought I’ll learn to knit, right. Like, how hard can it be? I mean grand­mas do it, right. It’s total­ly offline, total­ly sep­a­rate, total­ly simple—I’ll get a nice fuzzy scarf out of it. I can do this. 

So I get a kid’s learn-to-knit book and I start­ed mak­ing a pothold­er. And it near­ly killed me. I think I start­ed over about a dozen times. And by the end of that project, I had three things. 

One, I had a real­ly kick­ass pot hold­er, which has pride of place in my house today. Two, I had mad respect for the grand­mas of the world, like you have no idea. And I had the rev­e­la­tion that knit­ting was just like coding. 

And this just blew my mind and I start­ed see­ing these sim­i­lar­i­ties every­where. And pret­ty soon this men­tal model: 

Became this:

So, today I’m gonna walk you through some of those areas of sim­i­lar­i­ty, and the pat­terns that I rec­og­nized, in the hopes it’ll just inspire your own cre­ativ­i­ty. Look, this isn’t some­thing you’re gonna learn in your job. It’s noth­ing you’re gonna need next week. But I real­ly believe that by look­ing at what you do in a new way, it makes you bet­ter at it. 

So les­son the first, if you learn noth­ing else from linux.conf let it be this. 

This? This is not knit­ting. [laugh­ter] Not knit­ting. This is cro­chet. This is not con­tempt cul­ture. I’m not look­ing down on the hook­ers here. Crochet is a per­fect­ly valid form of expres­sion. It is not knit­ting, though. So it uses a sin­gle hook. It’s got a ball of yarn, you make stuff. Crochet’s real­ly great for com­plex three-dimensional shapes. And if you’re into math go home tonight and Google cro­chet maths,” and then next year you can be up here doing a talk on cro­cheted hyper­bol­ic geometry. 

This is knit­ting. Knitting is done with at least two nee­dles, some­times more. It’s involves the sequen­tial pro­cess­ing of stitch­es from one nee­dle on to the other. 

Now every knit­ter learns when they start out that there are actu­al­ly real­ly only two stitch­es: knit and purl. So the first thing I real­ized right off the bat was knit­ting’s bina­ry. And to a com­put­er geek like us, that implies I can use it to encode pret­ty much any­thing dig­i­tal. And I start­ed see­ing exam­ples of this everywhere. 

So for exam­ple I could com­bine knits and purls to make rib­bing for a beanie, like for hat. So this is called the Decoder Hat by Zabet Stewart, and it encodes up to twelve char­ac­ters, in ASCII, in bina­ry, at eight stitch­es per char­ac­ter. So obvi­ous­ly that is a pret­ty hard mem­o­ry lim­it, a mes­sage length of only twelve char­ac­ters, deter­mined of course by the size of your own head. 

Now if you want­ed to knit some­thing longer, you could knit a scarf. So this scarf here is the source code to rav​el​ry​.com, which is basi­cal­ly Github for knit­ters, with knits as the ones and purls as the zeros. 

Now, if you’re more of a black­hat you could even knit a virus. In 2001 a team of activists did just that. They knit­ted the source code to the Code Red com­put­er virus into a fluffy red scarf. You could wrap it around your neck and walk across any bor­der in the world. No fire­wal­l’s pickin’ that up. 

If you want­ed some­thing more styl­ish you could do cables, I’m a big fan of cables. The hat on the left here rep­re­sents the num­bers from zero to fif­teen in bina­ry nota­tion depend­ing on where the cable cross­es occur. And the scarf on the right has a hid­den mes­sage in bina­ry revealed by cables that actu­al­ly look like lit­tle ones and zeros. 

If you pre­fer col­or you could use the width of knit­ted stripes in dif­fer­ent col­ors to encode a char­ac­ter set. The stripes on this guy’s jumper of course spell out the clas­sic first pro­gram­ming exercise—say it with me, Hello, world.” 

If you want to get super lit­er­al you can actu­al­ly knit ones and zeros into your scarf. I’m hap­py to tell you the aver­age scarf, depend­ing on how tall you are, will hold about 120 bytes of infor­ma­tion. Just shy of a tweet. 

Of course not all data is text. Did you know in World War II the Belgian resis­tance recruit­ed lit­tle old ladies who lived near train­yards to watch the German trains and secret­ly knit their move­ments into their projects. It’s true, I saw it on QI

In more mun­dane exam­ples, on the left here is the Scoreboard scarf, which is a record of a sports team’s sea­son, with all of their points in one col­or and all their oppo­nents points in anoth­er col­or. I real­ly hope he’s bar­rack­ing for the grays. And on the right is a sky scarf, where the col­or of every row is the col­or of the sky above the knit­ter on the day that they knit­ted it. 

Now my last exam­ple of knit­ted and encod­ed data actu­al­ly won me a sec­ond prize at the Sydney Royal Easter Show a few years back. So ladies and gen­tle­men, I give you the knit­ted QR code mit­ten. It does work. It was sur­pris­ing­ly dif­fi­cult to get it to work. I mean, QR codes rely on things being real­ly square and knit­ted stitch­es as some of us know are inher­ent­ly wider than they are tall. So I had to do a lot of pro­to­types on dif­fer­ent thick­ness­es of wool, and even­tu­al­ly got— I hit upon the solu­tion, which in tech­ni­cal terms was to stretch the hell out of it…and then even­tu­al­ly got one that reads. So if you scan it, it points to a URL on my web­site that has the pat­tern for the mit­tens. So they’re self-replicating. 

Okay, so back to my sto­ry. So once I had the basic mechan­ics of knits and purls down it was time to learn to read pat­terns. Now the very first line of any knit­ting pat­tern looks some­thing like this, Cast on 24 stitch­es.” And that means to cre­ate that ini­tial row of loops on the nee­dle. Well I looked at that and my brain imme­di­ate­ly rec­og­nized well that’s just a for loop. You know, it’s code exe­cut­ing repeat­ed­ly a cer­tain num­ber of times. So my brain kind of trans­lat­ed it into code. You know some­thing like this, like a very sim­ple lit­tle for loop with a vari­able that calls stitch.castOn() 24 times. 

Okay. I can do that. 

So anoth­er real­ly com­mon instruc­tion you see is Repeat to end of row.” Well that’s a while loop. So you get code exe­cut­ing repeat­ed­ly again based on a giv­en boolean con­di­tion, and the con­di­tion in this case being have you got­ten to the end of the row yet?” If not, keep going. So again, real­ly sim­ple lit­tle while loop. While the expres­sion not at end of row” is true, just keep knitting. 

So that was all mak­ing sense. So once I fin­ished my pothold­er even­tu­al­ly, I was itch­ing to move onto gar­ments. And I picked out a jumper pat­tern, I opened it up, and the first thing I saw was this: Cast on 242 (256, 270, 284) stitch­es.” So I puz­zled through that and I real­ized these cor­re­spond to sizes. 

So, there are four gar­ment sizes at the start of the pat­tern. So here’s an exam­ple for a cardi­gan. So let’s assume I want to knit the 38″ chest size. Then I just need to cast on the num­ber of stitch­es that cor­re­spond. So the first one of every group before. So real­ly, this is a switch state­ment. This is code that allows the val­ue of a vari­able or expres­sion to change via mul­ti­way branch. 

And so I set a vari­able for my stitch size and then based on that I cast on the appro­pri­ate num­ber of stitch­es. So in this case 242

Now some pat­terns espe­cial­ly if they’re for kids and adults have a lot of switch state­ments. And each case usu­al­ly involves more than just a sin­gle vari­able chang­ing. So you might have whole sec­tions of the pat­tern you use or don’t use. And that leads me to the next con­cept, sub­rou­tines. So you know, in a pro­gram we might call these pro­ce­dures or func­tions or meth­ods. Well these are every­where in knit­ting. You know, if a pat­tern uses a par­tic­u­lar stitch pat­tern, they get declared in a sep­a­rate block at the start and then just invoked wher­ev­er you need. 

So here’s an exam­ple where a pat­tern has two spe­cif­ic stitch pat­terns, Twisted Rib” and Twisted Rib in the round.” And then in the actu­al instruc­tions, the twist­ed rib func­tion is invoked with the phrase Work in Twisted Rib.” 

Now anoth­er way that pat­terns declares sub­rou­tines is with charts, espe­cial­ly if they’re com­pli­cat­ed. So here’s some exam­ples from a cable cardi­gan, you know. There might be one chart for the front, one for the sleeve, and one for the col­lar. Now the real fun hap­pens (and the knit­ters know this) when you have more than one of these sub­rou­tines hap­pen­ing at the same time. And that actu­al­ly takes us into the realm of corou­tines, which some of you know are a spe­cial class of sub­rou­tines. So sub­rou­tines start and fin­ish and don’t hold state. But corou­tines can exit my call­ing or yield­ing to oth­er corou­tines and then lat­er come back to the point where they left off. It’s like hit­ting the pause but­ton. And you can also have mul­ti­ple instances of a giv­en corou­tine at once. 

Now in knit­ting you real­ly see this use with very com­pli­cat­ed lace and cable pat­terns. I start­ed knit­ting this mon­ster last year. It’s called mar­gen [sp?]. It involves twen­ty dif­fer­ent charts with fifty-six instances of them in use at any giv­en time. Knitters, this is row one:

Each one of those let­ters cor­re­sponds to a dif­fer­ent chart, which vary in length from two rows long to sixty-six. You could even look at this is a type of inter­leaved mul­ti­thread­ing (pun very much intend­ed) where the CPU, which in this case is my brain, has to take a new instruc­tion from each corou­tine in turn. And depend­ing on how much RAM I have avail­able, things can grind to a halt. This is not the type of pat­tern you knit at the pub. 

So I’m going to switch a lit­tle bit now and talk about pat­tern lan­guages and how they relate to pro­gram­ming lan­guages in gen­er­al. So in case you did­n’t know there’s no sin­gle world­wide knit­ting author­i­ty. Everybody writes their pat­terns dif­fer­ent­ly. There’s mul­ti­ple com­pet­ing stan­dards. That’s kind of anoth­er way it’s like programming. 

So the mind-blowing thing is that the his­to­ry of pro­gram­ming lan­guages actu­al­ly begins with tex­tiles. And I know some of you are prob­a­bly famil­iar with this. What is this?

This is a jacquard loom, invent­ed in 1798 by Joseph Marie Jacquard. And what is on the front of it? Punch cards. Jacquard devel­oped this forty years before Babbage wrote of using it for the Analytical Engine. So have a look at those punch cards, and then look at this mod­ern knit­ting stitch chart. 

Pretty sim­i­lar. So when exe­cut­ed this pat­tern cre­ates a stitch called moss stitch.” The blank squares are a knit stitch and the dots are purls. This is effec­tive­ly bina­ry. This is knit­ter’s machine code, you know. First-generation pro­gram­ming lan­guage. There’s no com­pil­er or assem­bler need­ed. It’s super easy for the CPU—remember, my poor brain—to exe­cute this. I see a blank, I knit. I see a dot, I purl. 

This is anoth­er exam­ple from 1935, a checker­board design. Instead of using sym­bols this uses col­ors, because this is actu­al­ly a mul­ti­col­or design. And charts like this are great for that because it pro­vides a form of error-checking. I can TDD by hold­ing my knit­ting up at any time and makin’ sure it looks like what it’s sup­posed to look like. 

It’s also data com­pres­sion. It saves a lot of space. So if this series of steps were writ­ten out in words it would take up a lot of paper and ink. And I know that because this par­tic­u­lar pat­tern includes it: pages, and pages, and pages. 

So as pat­terns got more com­pli­cat­ed pub­lish­ers real­ized they could save space in this way. And they could pro­vide even more infor­ma­tion by adding more sym­bols in. 

So this exam­ple’s from the 50s and it uses five dif­fer­ent typo­graph­ic sym­bols to rep­re­sent dif­fer­ent instruc­tions, to get an addi­tion­al lev­el of abstrac­tion here. This is a second-generation pro­gram­ming lan­guage. It’s like assem­bly for knit­ters. You know, I could read it but to actu­al­ly knit it I have to trans­late those sym­bols into the appro­pri­ate actions. And since these par­tic­u­lar sym­bols aren’t widely-used, it’s not very portable. Like I’m sure the oth­er knit­ters in the room are going, Roman numer­al 2, what the hell is that?” Like, it’s hard. And so it’s also no longer a one-to-one match with the out­put. I can’t eas­i­ly hold my knit­ting up and make sure it looks right. I know there’s dark lines on there but with­out those it’d be real­ly hard to do error-checking. 

So mod­ern knit­ting charts like this one try to bal­ance abstrac­tion and porta­bil­i­ty with faith­ful­ness to the out­put. We still don’t have a worldwide-agreed stan­dard but we’re get­tin’ there, so the sym­bols are pret­ty wide­ly used. And they look like what they’re rep­re­sent­ing. Like the cir­cles are for yarn overs, which make holes. Forward and back­wards slash­es rep­re­sent decreas­es, because they lean to the left or the right. A cen­tered three-to-one decrease is that sort of bird foot-lookin’ thing. So it con­tains a lot more infor­ma­tion. Like between the sym­bols and the col­ored lines you get like nine pieces of infor­ma­tion in a very com­pact lit­tle space. Looks good. 

But some knit­ters think this can be tak­en fur­ther. The prob­lem they say is that grid. So remem­ber this from my intro. This is called feath­er and fan stitch. And you see it kind of undu­lates up and down real­ly nice­ly. But you don’t get that in an orthog­o­nal grid, you know. You get this: 

Which is con­cise and read­able and all those good things…but does­n’t look like the end prod­uct. So a new syn­tax has pro­posed called Stitch Maps. It’s basi­cal­ly the fourth gen­er­a­tion of knit­ting pat­tern lan­guages, knit­ting charts. And it looks like this: 

And the idea’s that stitch maps let you see how parts of a stitch pat­tern fit togeth­er. So not just the sequence along a giv­en row, but how they inter­act row to row, or clock cycles if you like. And the real­ly cool thing is that stitch maps are com­piled from a domain-specific lan­guage called knit­s­peak. So you can actu­al­ly go to the Stitch Maps web site there, and enter a stitch pat­tern like this: 

This is knit­s­peak, it looks just like a nor­mal knit­ting pat­tern. And it will com­pile that and turn it into a visu­al­iza­tion that looks like this: 

So this is pret­ty much state of the art when it comes to knit­ting charts. 

But what about text pat­terns? So they’ve evolved quite a bit, too. So the first text pat­tern I can find in the English lan­guage was pub­lished in 1655. This is what it looks like, The order how to knit a Hose:” 

Which is basi­cal­ly how to knit a sock. So I know it looks impen­e­tra­ble, but if you’re a knit­ter you can kin­da, sor­ta start trans­lat­ing it, it makes a lit­tle bit of sense. But the UX is ter­ri­ble. It’s long and vague and hard to follow. 

So 200 years lat­er, we’re get­tin’ there. This is 1846. It’s a lot more read­able, you know. The cast on row’s clear­ly marked. We’re using some abbre­vi­a­tions to make things more con­cise. That’s all good. But what’s not great is you know, we’ve still got white­space and indent­ing all over the place. And the abbre­vi­a­tions aren’t just not-intuitive, they’re mis­lead­ing. The P3 here? P does­n’t stand for purl. It stands for plain stitch, which nowa­days we call knit. And the B stands for back­stitch, which is purl. So it’s exact­ly reversed. This is like the whole big-endian/little-endian thing. Like, if I give this chart to anoth­er knit­ter and they don’t know the intend­ed schema, they get the exact reversed output. 

So this is a mod­ern knit­ting pat­tern, anal­o­gous to a third-generation pro­gram­ming lan­guage. So, clear and easy to fol­low, stan­dard abbre­vi­a­tions, bro­ken down into mod­ules, you can swap em in and out. User expe­ri­ence is pret­ty good but…those switch state­ments. I just hate them. And there are so many of them. So again, some knit­ters think we can do better. 

Enter KnitML. KnitML is an open source project with a goal to pro­mote a new inter­na­tion­al stan­dard, an inter­me­di­ate for­mat for knit­ting pat­tern expres­sion. Knitting pat­terns are algo­rithms. And by for­mal­iz­ing a stan­dard in this way, we can allow com­put­ers to make deci­sions about them. And that allows for all sorts of use­ful oper­a­tions. I could down­load a pat­tern with just my size select­ed. I could have it in English or French or German. I could use charts or words, whichev­er I pre­fer. I could even use the abbre­vi­a­tions I like. It could even com­pute out those occa­sion­al­ly mathematically-complex things like increase 17 stitch­es even­ly over 113,” you know. 

And it would have advan­tages for design­ers too, because they could write a pat­tern in the way that makes sense to them, know­ing that their audi­ence could down­load it in the way they pre­fer. And more cru­cial­ly, they could use tests and val­i­da­tion to check for errors. So many knit­ting pat­terns have errors. And they could even use a visu­al­iz­er to pre­view the output. 

So this is what KnitML looks like. And…it’s not par­tic­u­lar­ly com­pact. And it does­n’t look like a tra­di­tion­al knit­ting pat­tern. But remem­ber this is just for com­put­ers to use; it’s an inter­me­di­ate for­mat. It’s not expect­ed that humans would ever direct­ly manip­u­late this. Instead the project pro­vides a tool called KnittingEL, which is Knitting Expression Language, and this is how the design­ers express their pat­tern. And it sort of looks like a pub­lished knit­ting pattern. 

But the project pro­vides Java-based soft­ware to con­vert KnittingEL pat­terns to KnitML which can then be passed on to sup­port­ing soft­ware, as I men­tioned, like val­ida­tors, ren­der­ers, and visualizers. 

So here’s one for exam­ple. This is an open source visu­al­iz­er called Knitter that process­es a KnitML pat­tern and pro­duces a three-dimensional mod­el of the result­ing knit­ted fab­ric. And you can even stretch it and see how it responds. 

This is just the tip of the ice­berg when it comes to open source knit­ting. Like if you go to Github tonight and look—and this screen­shot is old, there’s prob­a­bly more. Hundreds of repos to play with. You know, Go lan­guage imple­men­ta­tions of knit­ting pat­tern parsers. You’ve got cus­tom row coun­ters for your smart­watch. Apps for JPEGs into knit­ting charts. The source code for knit­ting ipsum gen­er­a­tor for your next web site. Instructions for wiring your own row counter which only slight­ly looks like a bomb. 

A knit­ted and felt­ed bag—this is a cool one—with a sewn-in Arduino where you actu­al­ly upload your knit­ting pat­tern, press the but­ton, and it lights up LEDs in pat­terns to indi­cate the next stitch­es that you’re meant to knit. 

Here’s one I myself designed and knit­ted, a beanie for Camp JS (Oh, I have it.) that uses a Gemma micro­con­troller, six LEDs, and a coin cell bat­tery to make myself vis­i­ble up on the misty moun­tain. Is it light­ing up? Oh no, maybe my— I’ll pow­er it up lat­er. Battery’s come undone.

Sweaterify is fun. This is a tool. Lets you upload an image and imag­ine it into an ugly Christmas sweater, and you can even down­load it. But more impor­tant­ly this was built by Mariko Kosaka, who did amaz­ing talk at JSConf last year called Knitting for Javascripters. It’s on YouTube. You should total­ly watch it. And in it she talked about one of the most pop­u­lar crossover knit­ting and pro­gram­ming activ­i­ties, which is hack­ing old knit­ting machines from the 70s and 80s. 

So these are very pop­u­lar. You can pick one up on eBay cheap. Brother made a ton of them. And hack­ing them usu­al­ly involves mak­ing your own ser­i­al cable and using it to upload your own cus­tom designs to the machine. And peo­ple are putting these to some very cool and very weird uses. 

So on the cool side the NeuroKnitting project plot­ted brain­wave activ­i­ty into a knit­ted pat­tern. They used a wear­able EEG to record users’ affec­tive states while lis­ten­ing to Bach’s Goldberg Variations, and then knit­ted that into a scarf on a hacked knit­ting machine. So that is his brain waves while lis­ten­ing to the music. 

Now on the weird side—and warn­ing: night­mare fuel—you’ve got artists like Andrew Salomone and his Machine-Knit Identity-Preserving Bitmap Balaclava. He Photoshopped images of his own head from every angle into a sin­gle rec­tan­gu­lar bitmap and then knit­ted it on a hacked knit­ting machine. 

So my favorite knit­ting tech project recent­ly is KnitYak. You guys might’ve seen it on Kickstarter. So Fabienne Serriere, fbz on Twitter, she’s using a hacked indus­tri­al knit­ting machine in a ship­ping con­tain­er in Portland (because of course) to knit provably-unique scarves using ele­men­tary cel­lu­lar automa­ta. So as a backer I get to choose my own col­ors, rule, and start­ing row. And the rule deter­mines how each sub­se­quent row changes depend­ing on the stitch­es that are encountered. 

So this is where things get real­ly inter­est­ing. Because one of the rules that I can select is Rule 110. And as some of you may know, around the year 2000 Matthew Cooke pub­lished a proof that Rule 110 is Turing com­plete and is capa­ble of uni­ver­sal com­pu­ta­tion. And it can be knit­ted. So giv­en an infinitely-long ball of wool, I can sim­u­late any Turing machine and by exten­sion the com­pu­ta­tion­al aspects of any pos­si­ble real-world com­put­er. Which is pret­ty mind-blowing. 

And that’s me. Thank you very much.

Further Reference

Session page

Help Support Open Transcripts

If you found this useful or interesting, please consider supporting the project monthly at Patreon or once via Cash App, or even just sharing the link. Thanks.