Difference between revisions of "1685: Patch"

Explain xkcd: It's 'cause you're dumb.
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(oops... I mis-pasted (my IP changed from last time))
(Explanation: i for i *in* a)
Line 36: Line 36:
  <font color="red">return </font>a
  <font color="red">return </font>a
  pivot<font color="red">=</font>a[<font color="light blue">0</font>]
  pivot<font color="red">=</font>a[<font color="light blue">0</font>]
  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]
  l<font color="red">=</font>[i<font color="red"> for</font> i <font color="red">in</font> a <font color="red">if</font> i<font color="red"><</font>pivot]
  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]
  r<font color="red">=</font>[i<font color="red"> for</font> i <font color="red">in</font> a <font color="red">if</font> i<font color="red">></font>pivot]
  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)))
  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)))
  <font color="red">return </font>quicksort(l)<font color="red">+</font>mid<font color="red">+</font>quicksort(r)
  <font color="red">return </font>quicksort(l)<font color="red">+</font>mid<font color="red">+</font>quicksort(r)

Revision as of 16:10, 25 May 2016

My optimizer uses content-aware inpainting to fill in all the wasted whitespace in the code, repeating the process until it compiles.
Title text: My optimizer uses content-aware inpainting to fill in all the wasted whitespace in the code, repeating the process until it compiles.


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.

The GNU 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.

The code appears to be written in 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.

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.

The original code was likely as follows:

import re
def isPrime(n):
	if n<=1:
		return False
	for i in range(2, int(n**0.5)+1):
		if n%i==0:
			return False
	return True
def isPrimeRegex(n):
	if re.match('^1?$|^(11+?)\1+$', '1'*n): 
		return False
	return True
def quicksort(a):
	if len(a) < 2:
		return a
	l=[i for i in a if i<pivot]
	r=[i for i in a if i>pivot]
	return quicksort(l)+mid+quicksort(r)

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.


[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).]
impo¤l me
		retern F(ise
	for i irararre(2, nint *n**n+5)+5):
		if n i==0
	re¤ irn True
defesisPrimcieg ¤x(cx
	if ge¤inatcx(r'^(1?| ?.1+?)\+)$'*n )1'*n):
		rerjrn Fa( e
dql qlsorsorn(a :
	if ¤n(a < 2:
		eteturn a
	pi= =r fa[0]
	l=pi=for j ln a i< i<pi<(t]()
	r=[l=for f in a) r i>viviv](vo)
	r¤lrurrriklcksckt(l) + r ¤ ¤quickrort(r)
[Caption below the panel:]
Protip: If you don't have access to the GNU patch tool, you can use the Photoshop one.

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


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 04:24, 25 May 2016 (UTC) I finally signed up! This comment is mine. NiceGuy1 (talk) 10:06, 9 June 2017 (UTC)

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. --Sherlock9 (talk) 05:03, 25 May 2016 (UTC)

Photoshop has a 'patch' tool but it has a very different function from a software patch. (talk) (please sign your comments with ~~~~)

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. Dansiman (talk) 05:56, 25 May 2016 (UTC)

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. -- 06:44, 25 May 2016 (UTC)

I think the second one is "isPrimeRegex". *cringe* 08:55, 25 May 2016 (UTC)

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 07:22, 25 May 2016 (UTC)

That indeed looks very much like it. I think this is worth mentioning. -- 11:22, 25 May 2016 (UTC)
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. -- Hkmaly (talk) 12:39, 25 May 2016 (UTC)

Do you think the use of pi is a reference to one of the other comics(I forgot which one...)?Transuranium (talk) 10:35, 25 May 2016 (UTC)Transuranium

I rather guess it is short for pivot. See quicksort for what the pivot does. -- 11:22, 25 May 2016 (UTC)

You know, it's theoretically possible for Photoshop to create compilable code in the esoteric programming language "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. 14:15, 25 May 2016 (UTC)

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. 15:25, 25 May 2016 (UTC)

It's because range(a, b) in Python means the interval [a, b) (excluding b). 15:41, 25 May 2016 (UTC)
That mismatched bracket in your comment is hurting me. 17:02, 25 May 2016 (UTC)
It's not mismatched; the right paren indicates the value's the upper limit but excluded. I'd include a right bracket in my response but I think that might make a compiler curse. Elvenivle (talk)

The line with re.match in the likely original code should have an "r" for "raw" before the first string thus:

 if re.match(r'^1?$|^(11+?)\1+$', '1'*n):

I am not changing it in the main explanation because I don't know what colour it should be and it's my first time contributing. - Charles W. 22:24, 25 May 2016 (UTC)

Seems like it has been changed by now. --Kynde (talk) 07:13, 26 May 2016 (UTC)

Has someone added this to the Protip category? 23:53, 25 May 2016 (UTC)

Uhm yes, it should be clear right below these comment on the main page? All categories are listed at the bottom of each page. --Kynde (talk) 07:01, 26 May 2016 (UTC)

It might be worth explaining the [pivot] * (len(a) - (len(l) + len(r))) since that threw me when I first saw it. Since l has the elements of a < pivot, and r has the elements of a > pivot, len(a) - (len(l) + len(r)) will be the number of elements in a that = pivot (which must be in the range [1, len(a)]), and these are then 'spliced' into the result between the result of quicksorting l and r. Jstout (talk) 19:48, 26 May 2016 (UTC)

Photoshop is available for a much lower price than mentioned in the explanation. Adobe offers an Photography Creative Cloud plan (currently US$9.99/month). This includes Photoshop CC, Lightroom CC and additional apps and online storage. http://www.adobe.com/creativecloud/photography.htmlThese Are Not The Comments You Are Looking For (talk) 22:44, 29 May 2016 (UTC)

Resemblance to Xerox number mangling issue

To me, this reminds me of the problem that a large set of Xerox copiers had. Their faulty use of image compression when scanning could cause portions of images to be replaced with similar portions, but the threshold of similarity was loose enough that numeric data would be subtly corrupted. For example, building plans and spreadsheet data could have numbers copied incorrectly, either of which could certainly have disastrous consequences. Documents were corrupted for a period as much as eight years before the problem was corrected, making legal archive data unreliable for this period, and some of the faulty machines may still be in use. http://www.dkriesel.com/en/blog/2013/0802_xerox-workcentres_are_switching_written_numbers_when_scanning (talk) (please sign your comments with ~~~~)

Now that you mention it... Although here it's a person intentionally doing harm to the image. 22:20, 26 May 2016 (UTC)
So that's what it was! I wondered why all the copies I could find of Concrete Mathematics had random font changes all over (and half the formulas came out wrong). 22:26, 26 May 2016 (UTC)
Wow. that's intense. 00:04, 27 May 2016 (UTC)
A couple of decades ago, the firm I was working for suddenly realised that one of its dot-matrix printers was causing problems. It was being used to print out specific validation information for archival, but the centre pin of the (vertical)print-head pin array was no longer striking. Out of 9 or perhaps 13 pins, it didn't represent much difference in the output normally, but the difference between a 0 and a 8 was whether that pin's contribution was two separated pixels, the middle of the two long verticals in the zero*, or a short horizontal sequence of dots representing the contact between the two small circles in the eight. The way the hardly-noticed absent row caused the character to be read meant that both read as zero, with no difference. (Other characters had problems, but usually did not look like anything else. There were no hyphens/minus-signs, but they might have rendered as whitespace if there had been.) This was not an ideal situation, and a different printer was swapped in ASAP.
* - This typeface's zero did not have a diagonal bar, of the type I even habitually handwrite, but confusion with O-for-Oscar characters was already not an issue due to context... 03:37, 27 May 2016 (UTC)

I think the party of the explanation that details OCR is more in depth than it really needs to be. Considering that the comic itself makes no reference to OCR, these details should be trimmed down considerably, or at least moved to a later point in the explanation after the more salient details. Dansiman (talk) 15:48, 28 May 2016 (UTC)