Talk:1685: Patch

Explain xkcd: It's 'cause you're dumb.
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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)

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 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)

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.

Now that you mention it... Although here it's a person intentionally doing harm to the image. 22:20, 26 May 2016 (UTC)