https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&feedformat=atom&user=108.162.222.29explain xkcd - User contributions [en]2026-04-15T16:51:35ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=1685:_Patch&diff=1208221685: Patch2016-05-25T15:48:44Z<p>108.162.222.29: oops... I mis-pasted (my IP changed from last time)</p>
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<div>{{comic<br />
| number = 1685<br />
| date = May 25, 2016<br />
| title = Patch<br />
| image = patch.png<br />
| titletext = My optimizer uses content-aware inpainting to fill in all the wasted whitespace in the code, repeating the process until it compiles.<br />
}}<br />
<br />
==Explanation==<br />
<br />
<br />
{{w|Adobe Photoshop}} is a commonly used software for image manipulation. One of its features is "content-aware inpainting", which allows the user to delete parts of the image and seamlessly replace the deleted sections with "patches" of texture from other parts of the image. <br />
<br />
The {{w|GNU}} {{w|Patch (Unix)|patch}} is a software program that replaces only parts of the code with an updated version, without requiring the user to download the entire source code. Here, it appears the author was told to "patch" the code, but used Photoshop to do this instead of GNU patch, with devastating results. Although the title text suggest that if you did this enough times the code would eventually compile, this would never happen. In fact, Photoshop could only edit an image of the text and not the text itself.<br />
<br />
The code appears to be written in {{w|Python_(programming_language)|Python}}, a programming language often referred to in xkcd. A few of the function names that can be recognized are "isPrime" and "quicksort", both elementary programming algorithms.<br />
<br />
The title text also explains that patch used the content-aware inpainting to fill in all the wasted whitespace in the code. In Python, whitespaces are used as a part of programming syntax (for example, new line of code are used instead of semicolon (;), and indents are used instead of curly brackets.<br />
<br />
The original code was likely as follows:<br />
<br />
<font color="red">import</font> re<br />
<font color="red">def<font color="purple"> isPrime</font></font>(n):<br />
<font color="red">if </font>n<font color="red"><=</font><font color="light blue">1</font>:<br />
<font color="red">return</font> <font color="light blue">False</font><br />
<font color="red">for</font> i <font color="red">in <font color="light blue">range</font></font>(<font color="light blue">2</font>, <font color="light blue">int</font>(n<font color="red">**</font><font color="light blue">0.5</font>)<font color="red">+</font><font color="light blue">1</font>):<br />
<font color="red">if</font> n<font color="red">%</font>i<font color="red">==<font color="light blue">0</font></font>:<br />
<font color="red">return<font color="light blue"> False</font></font><br />
<font color="red">return <font color="light blue">True</font></font><br />
<font color="red">def <font color="purple">isPrimeRegex</font></font>(n):<br />
<font color="red">if</font> re.match(<font color="blue">'</font><font color="light blue">^</font><font color="blue">1</font><font color="red">?<font color="light blue">$</font>|<font color="light blue">^</font><font color="blue">(11</font>+?<font color="blue">)</font><font color="green">\1+</font><font color="light blue">$</font></font><font color="blue">'</font>, <font color="blue">'1'</font><font color="red">*</font>n): <br />
<font color="red">return <font color="light blue">False</font><br />
<font color="red">return<font color="light blue"> True</font></font></font><br />
<font color="red">def<font color="purple"> quicksort</font></font>(a):<br />
<font color="red">if <font color="light blue">len</font></font>(a) <font color="red">< <font color="light blue">2</font></font>:<br />
<font color="red">return </font>a<br />
pivot<font color="red">=</font>a[<font color="light blue">0</font>]<br />
l<font color="red">=</font>[i<font color="red"> for</font> i <font color="red">ln</font> a <font color="red">if</font> i<font color="red"><</font>pivot]<br />
r<font color="red">=</font>[i<font color="red"> for</font> i <font color="red">ln</font> a <font color="red">if</font> i<font color="red">></font>pivot]<br />
mid<font color="red">=</font>[pivot]<font color="red">*</font>(<font color="light blue">len</font>(a)<font color="red">-</font>(<font color="light blue">len</font>(l)<font color="red">+</font><font color="light blue">len</font>(r)))<br />
<font color="red">return </font>quicksort(l)<font color="red">+</font>mid<font color="red">+</font>quicksort(r)<br />
<br />
isPrime and quicksort are standard python implementations of simple algorithms (although you would not generally write a sorting algorithm in python as there are built-in algorithms available). isPrimeRegex uses the re module to detect if a number is prime by seeing if a string containing that many 1s can be matched to 2 or more copies of some string containing at least 2 1s.<br />
<br />
==Transcript==<br />
:[The panel displays part of a code, in four different colors (red, light blue, green and purple) as well as normal black text, which due to image editing is difficult to read. The first and last line are partly obscured by the frame of the panel. Here below is an attempt to transcribe the code, using the sign "¤" for anything not easily transcribed. Feel free to add other signs instead of these that looks more like the one in the image (and also improve the attempted transcription if possible).]<br />
<font color="red">impo¤l </font><font color="purple">me</font><br />
<font color="red">doo</font><font color="purple">PisPS¤me</font>(n):<br />
<font color="red">r</font>(<font color="purple">¤</font>n<font color="red"><</font>n,<font color="light blue">1</font>:<br />
<font color="red">retern</font> <font color="light blue">F</font>(<font color="light blue">ise</font><br />
<font color="red">for</font> i <font color="red">ir</font><font color="light blue">ararre</font>(<font color="light blue">2</font>, <font color="light blue">nint</font> <font color="red">*</font>n<font color="red">**</font>n<font color="red">+</font><font color="light blue">5</font>)<font color="red">+</font><font color="light blue">5</font>):<br />
<font color="red">if</font> n i<font color="red">==</font><font color="light blue">0</font><br />
<font color="red">ret¤¤nrs</font><font color="light blue">elsel</font>:<br />
<font color="red">re¤ irn </font><font color="light blue">True</font><br />
<font color="red">defe</font><font color="purple">sisPrimcieg ¤x</font>(c<font color="purple">x</font><br />
<font color="red">if</font> <font color="purple">g</font>e<font color="purple">¤i</font>natc<font color="purple">x</font>(<font color="red">r</font>'<font color="light blue">^</font><font color="blue">(1</font><font color="red">?| ?.</font><font color="blue">1</font><font color="red">+?</font><font color="blue">)</font><font color="lime">\+</font><font color="blue">)</font><font color="light blue">$</font>'<font color="red">*</font>n <font color="blue">)1'</font><font color="red">*</font>n):<br />
<font color="red">rerjrn </font><font color="light blue">Fa</font><font color="blue">(</font><font color="light blue"> e</font><br />
<font color="red">Letyl</font><font color="purple">nr</font><font color="light blue">Trl</font><br />
<font color="red">dq</font><font color="purple">l qlsorsor</font><font color="light blue">n</font>(a :<br />
<font color="red">if </font><font color="light blue">¤n</font>(a <font color="red">< </font><font color="light blue">2</font>:<br />
<font color="red">eteturn </font>a<br />
pi<font color="red">= =r f</font>a[<font color="light blue">0</font>]<br />
l<font color="red">=</font>pi<font color="red">=for</font> j <font color="red">ln</font> a i<font color="red"><</font> i<font color="red"><</font>pi<font color="red"><</font>(t]<small>(</small>)<br />
r<font color="red">=</font>[l<font color="red">=for f in</font> a) <font color="red">r</font> i<font color="red">></font>viviv]<small>(</small>vo)<br />
mid<font color="red">=</font>[pi[<font color="red">*</font>t]<font color="red">*</font>(<font color="light blue">l</font><font color="red">*</font>t<font color="light blue">,</font>(a)<font color="red">-</font>(<font color="light blue">len</font>pi<font color="light blue">enlen</font>(c)))<br />
<font color="red">r¤lrurrr</font>iklcksckt(l) <font color="red">+</font> r ¤ ¤quickrort(r)<br />
<br />
:[Caption below the panel:]<br />
:Protip: If you don't have access to the GNU ''patch'' tool, you can use the Photoshop one.<br />
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{{comic discussion}}<br />
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[[Category:Comics with color]]<br />
[[Category:Protip]]<br />
[[Category:Programming]]</div>108.162.222.29https://www.explainxkcd.com/wiki/index.php?title=Talk:1685:_Patch&diff=120820Talk:1685: Patch2016-05-25T15:41:33Z<p>108.162.222.29: </p>
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<div><!--Please sign your posts with ~~~~--><br />
Hey, I'm first! Guessing the Bot only JUST created this, it was mere minutes after midnight EST when I landed on this page. Unfortunately this is a comic I'm less capable of explaining. From the looks of it, his Photoshop Patch turned what looks like C code into gobbledegook by filling in several of the spaces (and I think even changing some of the characters, possible with characters which fill more of the space). - NiceGuy1 [[Special:Contributions/108.162.218.77|108.162.218.77]] 04:24, 25 May 2016 (UTC)<br />
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This appears to be Python code. Note the "def" keyword, how "for i in [garbled]:" is used rather than C's for syntax, and how there are no semicolons or braces. --[[User:Sherlock9|Sherlock9]] ([[User talk:Sherlock9|talk]]) 05:03, 25 May 2016 (UTC)<br />
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Photoshop has a 'patch' tool but it has a very different function from a software patch.<br />
:An explanation of Photoshop's patch tool might be helpful in identifying patterns in what pixels were changed by it, perhaps facilitating the identification of some likely characters. [[User:Dansiman|Dansiman]] ([[User talk:Dansiman|talk]]) 05:56, 25 May 2016 (UTC)<br />
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The first function looks like "isPrime" and seems to check if a number is prime. The last function looks like "quicksort". Both are common functions you create when learning programming. Not sure about the second one, but it looks like it uses regular expressions. -- [[Special:Contributions/198.41.242.242|198.41.242.242]] 06:44, 25 May 2016 (UTC)<br />
:I think the second one is "isPrimeRegex". *cringe* [[Special:Contributions/141.101.104.25|141.101.104.25]] 08:55, 25 May 2016 (UTC)<br />
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Second function looks like a function to check if number is a prime using Regex (described here http://www.noulakaz.net/2007/03/18/a-regular-expression-to-check-for-prime-numbers/). I don't know if it deserves some special mention, but at least to me (non-programmer) it looks like one of the most arcane things you can do in programming [[Special:Contributions/141.101.80.79|141.101.80.79]] 07:22, 25 May 2016 (UTC)<br />
:That indeed looks very much like it. I think this is worth mentioning. --[[Special:Contributions/198.41.242.240|198.41.242.240]] 11:22, 25 May 2016 (UTC)<br />
:Note that mathematically speaking, that regular expression is NOT regular expression - use of backreference in match is one of originally perl extension which makes it much more powerful (and much slower in some cases). It's just that both python and ruby already copied most of perl extensions of regular expressions. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 12:39, 25 May 2016 (UTC)<br />
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Do you think the use of pi is a reference to one of the other comics(I forgot which one...)?[[User:Transuranium|Transuranium]] ([[User talk:Transuranium|talk]]) 10:35, 25 May 2016 (UTC)Transuranium<br />
:I rather guess it is short for pivot. See {{w|quicksort}} for what the pivot does. --[[Special:Contributions/198.41.242.240|198.41.242.240]] 11:22, 25 May 2016 (UTC)<br />
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You know, it's theoretically possible for Photoshop to create compilable code in [https://esolangs.org/wiki/Piet the esoteric programming language] "[http://www.dangermouse.net/esoteric/piet.html Piet]". But unless there's a way to turn off the Patch tool's antialiasing, it'll be practically impossible for patches larger than a single pixel. [[Special:Contributions/108.162.237.220|108.162.237.220]] 14:15, 25 May 2016 (UTC)<br />
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I don't really know anything about programming, but it looks like it's checking for factors of n from 2 to sqrt(n)+1. Why would it need to check any number larger than sqrt(n) though? If i>sqrt(n), then ij=n implies that j<sqrt(n), and j should already have been found. So the largest integer you need to check is floor( sqrt(n) ), which is in the range from 2 to sqrt(n). Checking ceiling( sqrt(n) ) for a non-square number seems redundant. [[Special:Contributions/108.162.237.250|108.162.237.250]] 15:25, 25 May 2016 (UTC)<br />
:It's because <code>range(a, b)</code> in Python means the interval [a, b) (excluding b). [[Special:Contributions/108.162.222.29|108.162.222.29]] 15:41, 25 May 2016 (UTC)</div>108.162.222.29