Wikipedia:Reference desk/Computing

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December 7[edit]

Streaming video display ratio[edit]

On many streaming websites, many videos with wrong aspect or display ratios exist (e. g., video is 16:9 but displayed as 4:3). Is there such a thing as a Firefox (57.0.1, 64-Bit on Windows 10 Home) plug-in or add-on where I can change any streaming video's display ratio on any page with one click, a lot like I can in VLC? The only such exact plug-in I could find could only do it for YouTube, and the other two I found only could tell my OS that my *MONITOR* would be 21:9 rather than 16:9. --2003:71:4E07:BB77:903C:110A:4DF3:BC7A (talk) 23:34, 7 December 2017 (UTC)

Maybe one of the first three results on this page can help? (((The Quixotic Potato))) (talk) 16:28, 8 December 2017 (UTC)
Well, thanks...I considered that my last resort because loading it into VLC will leave a permanent copy hogging my C: drive space that I'd have to clean regularly to keep my system running, hence I was hoping for a one-click in-browser solution. --2003:71:4E07:BB40:5DB9:6E6A:B4D1:170 (talk) 03:27, 9 December 2017 (UTC)
Okay, so I didn't find any plugin that did exactly what I wanted to do, so first I've installed that "Open in VLC" addon from your link. Doesn't do shit. Checked the settings and found it was looking for a VLC in totally the wrong place on C:, and since it was the only option at all, I fixed it, and still it doesn't do shit. So next I've installed YouTube 2 Player from the same URL above. When I try that, it only prompts me with the error msg, "Fix your options" and opens the options tab, but I can't change anything because it's all greyed out! All I can do is change the default player from this ominious default "MOX" player to VLC. Result: Jack shit happens upon clicking the "Send to external player" just as well, other than that now my RAM usage immediately jumping from 2 up to its absolute maximum 16 GB *AT ONCE* and that's it! Not even my task manager will show any new instance of VLC popping up secretely somewhere under thre hood! Plus, Firefox hogs my entire 16 GB of RAM and incredibly slows down my entire system from it until I kill it by means of CTRL + ALT + DEL. --2003:71:4E07:BB11:F008:B7DF:883A:442B (talk) 23:54, 12 December 2017 (UTC)
So now I'm through with *EVERY SINGLE ONE* of those addons from your link and none of them does a damn thing, even on YouTube which they are all frikkin' designed for, and even if you fix the program path! But at least none of the others hog my RAM to do nothing at all, as does YouTube Player 2. --2003:71:4E07:BB11:F008:B7DF:883A:442B (talk) 00:11, 13 December 2017 (UTC)

December 8[edit]

how to delete files on my phone[edit]

It's a Samsung Galaxy S6. Today I received a message that I'm running out of space and that some apps might not run as a result. The message said 19 GB of my space was occupied by Pictures, and I decided to delete them all.

In the Samsung folder I found My Files, which showed six categories, including images. When I clicked that, I saw all the images but no way to delete them. There were options to edit, share, sort by, and settings.) When I clicked on one of the pictures, I got the message, "Unable to open Gallery. There is not enough storage space to open Gallery. Go to My Files, then delete some files."

I would love to. Can you help? Thanks, --Halcatalyst (talk) 00:07, 8 December 2017 (UTC)

A Web search for "samsung galaxy delete file" looks promising. You can also delete (as well as copy to or from the device) files on the phone from a PC if you connect the phone to a PC with a USB cable. --47.157.122.192 (talk) 03:43, 8 December 2017 (UTC)
Thank you. I found an excellent reference" [1] --Halcatalyst (talk) 15:37, 8 December 2017 (UTC)

VHDL is Sequential or Concurrent/Parallel?[edit]

If VHDL is a concurrent language, then how it handles conditional statements (like if, elsif, case) which proceeds sequentially? The confusion is that how can a concurrent language deal with sequential conditional statements? Sunnynitb (talk) 13:51, 8 December 2017 (UTC)

VHDL captures both concepts. A process is a sequential operation, but a VHDL design can have multiple (often many) processes, which can operate concurrently. The language has various mechanisms, including process sensitivity and wait statements, which allow the designer to specify how otherwise concurrent operations can interact. -- Finlay McWalter··–·Talk 15:10, 8 December 2017 (UTC)
If there is any material or link regarding this question, please give me. Thank You. Sunnynitb (talk) 18:19, 8 December 2017 (UTC)
http://www.tkt.cs.tut.fi/kurssit/1426/S11/Lectures/TKT-1426_lect_7.pdf -- Finlay McWalter··–·Talk 21:07, 8 December 2017 (UTC)

Security question[edit]

I just attempted to visit http://www.allmusic.com/artist/reverend-jim-howie-mn0001168557 but was presented with a huge warning about a worm, and it autoplayed an audio file telling me to call so-and-so about the situation. (1) If you have a really solid antivirus/firewall/whatever, could you visit the page and help me understand what's going on? I'm guessing that it's somewhat of a hoax (warning! virus! call this Microsoft number which actually is our number, and we'll take over your computer, thank you very much), but I'm not clear. (2) AllMusic appears to be a major commercial site; unless someone hacks their databases, how is this possible? If it were user-generated, I'd guess that it's comparable to the GNAA attacks that we've sustained (e.g. Wikipedia:Administrators'_noticeboard/IncidentArchive960#Spam_/_"hack"_(loosest_sense)_edit_needs_followup), but our article doesn't make it sound like a usergenerated site. Nyttend backup (talk) 20:47, 8 December 2017 (UTC)

For what it's worth, I see an entirely normal site with no scary warnings. -- Finlay McWalter··–·Talk 20:58, 8 December 2017 (UTC)
Huh. I wonder if I've got something on my computer...I think I'll talk with our IT department about this computer. Nyttend backup (talk) 21:24, 8 December 2017 (UTC)
You probably have malware on your computer. Allmusic isn't the problem. (((The Quixotic Potato))) (talk) 21:49, 8 December 2017 (UTC)
https://transparencyreport.google.com/safe-browsing/search?url=allmusic.com It is the reference desk after all. (((The Quixotic Potato))) (talk) 22:41, 8 December 2017 (UTC)
  • ...unless someone hacks their databases... - mandatory XKCD. Defacing a website is easier than making arbitrary calls to the underlying database (when there is one), and even more so than editing the underlying database. TigraanClick here to contact me 12:41, 9 December 2017 (UTC)
  • Didn't know that. "Takes down the website of the CIA" I would understand as being a DDOS or something of the sort, but aside from "merely" crashing a website, I didn't know that it was possible to affect the way that someone viewed it, unless you compromised their servers or you infected the computer being used to view the site. Nyttend backup (talk) 14:22, 9 December 2017 (UTC)
Well, yeah, denial of service is also easier than getting write access to their web server, and that may well be the meaning of the XKCD. You are correct than (barring a compromise of the client's computer/browser) the attacker needs some ability to change the contents of the setup that displays the website, but that setup is exactly what is usually meant by "database". (Actually, there are network attacks, for instance hijacking the URL-website correspondance - see DNS spoofing, cybersquatting - or man-in-the-middle attacks to intercept and forge traffic between the client and the server; they do not involve write access to the servers)
Still, the server that the client's browser communicates with is not always the only piece of the setup that is used to display webpages. See [2] for some examples of what can happen behind the front page. If you have a heap of data ("database") from which the reader of your webpage is allowed to read fragments, a proper setup is to have the web server allowed to make read requests to a database server that cannot be accessed directly from the internet (at least without a login). With such a setup, should the web server be compromised (which is more likely since it will listen to stuff that is sent to him via the internet), the attacker will only be able to make requests that are allowed by the database server - hence you have a better chance to avoid the database from been written to ("hacked"), or read in places that are not supposed to be read, than if it was stored on the same environment. TigraanClick here to contact me 12:33, 11 December 2017 (UTC)

December 9[edit]

USB Hub[edit]

I have a new, powered, USB Hub, and though I know that it is plugged into a power outlet and is plugged into the back of my Apple Desk-Top, none of the "keys" (or whatever they are called) show-up on the 'Desktop', does anyone have any ideas as to why please?194.126.80.63 (talk) 00:45, 9 December 2017 (UTC)

I know very little about Macs and I am not sure what you mean when you say "keys", but I think that if you (for example) connect an external hard drive to that USB hub the drive will show up on the desktop, but the USB hub itself does not. Its just a bunch of empty extra USB ports, and they are only displayed on the desktop if you connect something to them. (((The Quixotic Potato))) (talk) 00:54, 9 December 2017 (UTC)
I know a bit more about Macs, and your understanding is correct. Also, not all hard drives can be powered via USB, not even via a powered hub - for most 3.5" drives, you still need an external power supply, or they won't turn on (and won't show up). --Stephan Schulz (talk) 00:59, 9 December 2017 (UTC)

Thanks for this, but each of the connections on the Hub have a portable programme 'key' plugged in and it is those that I should expect to show up on the "Desktop". Sorry not to remember what these portable "keys" are properly called! (Memory Stick is it?) — Preceding unsigned comment added by 194.126.80.63 (talk) 07:28, 9 December 2017 (UTC)

Each USB flash drive should show up as a separate drive on the desktop. If they are not showing after a short delay then perhaps there is a faulty connection somewhere? Dbfirs 08:22, 9 December 2017 (UTC)
Can you try connecting your keyboard or mouse to the USB hub? After a few seconds delay the keyboard LEDs will come on, and the mouse's LED will come on (assuming it's on optical mouse). LongHairedFop (talk) 11:33, 9 December 2017 (UTC)
In addition to what LongHairedFop has suggested, you should also try plugging these "keys" into the exact same port the hub is plugged into and make sure they all work. Nil Einne (talk) 12:14, 9 December 2017 (UTC)

Thanks again, yes all the Memory Sticks work independently when connected into the computor, but don't work when reinstalled into the 'Cerulian' Hub. The Power Light is 'on' on the hub so it is not a power problem.;just weird! — Preceding unsigned comment added by 194.126.80.63 (talk) 15:53, 9 December 2017 (UTC)

So you did try the hub with something else like a keyboard or mouse and this worked? If so, final question, did you try with only one stick plugged into the hub? Nil Einne (talk) 06:51, 10 December 2017 (UTC)

Yes, and the individual Memory Sticks when plugged directly into the computor backside, work fine, but not when put into the Hub. — Preceding unsigned comment added by 194.126.80.63 (talk) 07:49, 10 December 2017 (UTC)

Does your hub work with any other devices (such as keyboard or mouse)? Have you tried it on a different computer? Dbfirs 15:43, 10 December 2017 (UTC)

I do not have access to another compute194.126.80.63 (talk) 07:52, 11 December 2017 (UTC)r unfortunately, and yes I tried with just one Memory Stick and that don't work either. I will give up I think and throw it out of the window. Many thanks for your interest.194.126.80.63 (talk) 07:52, 11 December 2017 (UTC)

You could take the hub to your local library and try it there. Have you tried your keyboard or mouse through the hub? Dbfirs 08:06, 11 December 2017 (UTC)

No but thanks for the idea, but both keyboard and mouse work wirelessly. My local library would not welcome me I don't think!194.126.80.63 (talk) 10:42, 12 December 2017 (UTC)

Is there a dongle for keyboard or mouse? Try moving it to the hub. LongHairedFop (talk) 20:19, 12 December 2017 (UTC)

No,there is no dongle.194.126.80.63 (talk) 07:08, 13 December 2017 (UTC)

Optimum number of threads on BOINC Primegrid LLR[edit]

Doing LLR tests on BOINC's PrimeGrid project on an i7, what is the optinum number of threads to run on an i7? When eight threads are running, the estimated time remaining doesn't decrease much. (I asked over there and didn't get a reply.) Bubba73 You talkin' to me? 20:19, 9 December 2017 (UTC)

The optimal time in FPU intensive tasks is usually equal to the number of physical cores - 4 in this case. Ruslik_Zero 20:50, 9 December 2017 (UTC)
Does this help? (((The Quixotic Potato))) (talk) 20:52, 9 December 2017 (UTC)
Yes, it does. Thanks to both of you! Bubba73 You talkin' to me? 21:24, 9 December 2017 (UTC)
Resolved

December 10[edit]

Programming vs. designing electronic circuits[edit]

How far is designing electronic circuits from writing programs? Couldn't the former be conceived as a kind of functional programming task where the signal has to move through several functions (electronic components) to output a result? It reminds me of the Unix pipeline. But is there any programming language that has built-in functions equivalent to components like transformers, resistances, capacitors and so on? --Hofhof (talk) 13:12, 10 December 2017 (UTC)

A typical example is an Engine control unit. A CPU follows a program, reading measurements and setting counter values read from a table in memory into a circuit which can be compared with a signalling control. In this example, the train is the cramshaft sensor. Values in the table are the ignition timing, begin and end of injecting fuel on each cylinder. The signalling control device is made in VHDL, the firmware in the CPU is C or assembler. --Hans Haase (有问题吗) 13:40, 10 December 2017 (UTC)
(ec)There are various hardware description languages that are used as part of Computer Aided Design tool chains. Verilog and VHDL come to mind as the most prominent examples for digital designs, but both have extensions for analog design. I'm pretty sure there also are dedicated languages for analog design. --Stephan Schulz (talk) 13:41, 10 December 2017 (UTC)
SPICE is the best-known circuit simulator for analog design. See also Category:Electronic circuit simulators. Tevildo (talk) 20:50, 10 December 2017 (UTC)
The two used to be very similar. Many many years ago, I maintained Litton Industries radar systems. Computers were becoming popular, but PC networking was still lacking. So, there were programmers. I wrote programs for DOS, Windows, and even the Commodore 64 in C. So, I knew how to program. Mainly, I worked on electronic circuits. Radars were a weird beast. The incoming information was analog. The output was an analog radar display with many digital lights and buttons. The circuitry in between was mostly logic circuits. The way I worked on it was by rewriting the logic circuits programming. Example: If the user presses the track button and the touch-screen coordinate matches a track coordinate, then enable the track display circuit. It took a couple months, but I rewrote the entire mess of over 50 circuit boards as a single program. As a result, when something very odd would happen, such as a 6 constantly showing up in the track number, I could look at the program and identify what logic could cause that problem. Then, I limit the scope of the problem to a few components and go in and fix it. That was the end of this type of work though. Once I had the program completed and I showed it to the Litton engineers, they started replacing all the circuits with a single computer. Three years later, all circuits were gone and it was just a computer. 209.149.113.5 (talk) 13:33, 11 December 2017 (UTC)

December 11[edit]

Font Designing Software[edit]

Which is the best software package, Windows usable, which can be used to make fonts from scratch without much ado, by an untrained user. Jon Ascton  (talk) 12:44, 11 December 2017 (UTC)

Google it. Quite a few people have made lists. There is no "best", it depends on your preferences. [3] [4] (((The Quixotic Potato))) (talk) 12:46, 11 December 2017 (UTC)

MS Outlook 2010[edit]

How to create password protection on an "Outlook.pst" file? A specific guide required please. 123.108.246.225 (talk) 16:34, 11 December 2017 (UTC)

Here you go. This kind of password protection is not very strong, and there are many tools that can remove the password protection [5]. (((The Quixotic Potato))) (talk) 16:44, 11 December 2017 (UTC)

MS OneNote 2010[edit]

I can password protect a section but not its "Notebook", could you give me a specific guide please. 123.108.246.225 (talk) 16:34, 11 December 2017 (UTC)

No, I cannot, because that is unfortunately not possible. Many people have asked for this feature, but as far as I know it has not been implemented (yet). [6] (((The Quixotic Potato))) (talk) 16:40, 11 December 2017 (UTC)

Duplicate Installations[edit]

Failed installations are displayed in the "Control Panel>All Control Panel Items>Recovery" window, thereafter following through the "Open System Restore" option, and it does not display in the "Control Panel>All Control Panel Items>Programs and Feature" options. E.g., I installed MS Office 2013…

1) What do I do? I wish to remove them off the PC...

2) I wish to try reinstalling but the problem is the preious data available. Will it replace as it is installing?

123.108.246.225 (talk) 16:34, 11 December 2017 (UTC)

Encryption help[edit]

I’ve tried using the built-in encryption facility for the MicroSD, it’s not helpful enough. Could you please refer me to a reliable app (or a PC software) I could use for password protection, that also works (requests for password entry) whenever the MicroSD is inserted in PC. A software that works on both platforms basically. 123.108.246.225 (talk) 16:34, 11 December 2017 (UTC)

Android Phone softwares[edit]

How do I transfer downloaded softwares available on my android via OTG cable to a pen drive, so that I can re-use them later when desired?

Plug n Play facility or installation exe with its folder is required to find, and I don't know what to do as I'm new in Android platform.

123.108.246.225 (talk) 16:34, 11 December 2017 (UTC)

Can not you just copy them to the pen-drive using a file manager? Ruslik_Zero 20:31, 11 December 2017 (UTC)
If your phone is not rooted, you probably won't be able to.
The apps are stored in /data/app (for user-installed software) and /system/app (for software that came with the phone.)
Unfortunately, If you try to find those folders without root access, you won't find them because they're hidden. ApLundell (talk) 21:07, 11 December 2017 (UTC)

December 12[edit]

Is there an Internet forum thread with ≥100,000 posts?[edit]

≥200,000? ≥a million? Sagittarian Milky Way (talk) 23:13, 12 December 2017 (UTC)

Posts made by humans? (((The Quixotic Potato))) (talk) 23:53, 12 December 2017 (UTC)
Yes by humans (though thanks for the funny image, I hadn't thought of AIs conversing @ kiloposts/second for.. something (data mining?)) Or are there human threads that get resurrected by literally millions of Viagra spams, all competing to be last? Or are you just surprised at the number? I've seen a >32,000 post, >1,600 page human thread (no spam) over a decade old but I don't know how big that is in the grand scheme of things. Sagittarian Milky Way (talk) 01:15, 13 December 2017 (UTC)
The forum index at https://www.thesamba.com/vw/forum indicates that the Bay Window Bus forum has a post count in excess of 1 million. Kreemoweet (talk) 04:39, 13 December 2017 (UTC)

December 13[edit]

Regex for Linux ifconfig[edit]

ipa=$(ifconfig | grep -Po "inet addr:\K[0-9]?[0-9]?[0-9]?\.[0-9]?[0-9]?[0-9]?\.[0-9]?[0-9]?[0-9]?\.[0-9]?[0-9]?[0-9]?")

This brings both external IP and internal (loopback) IP. Why does the loopback being brought as well? I can use another grep to remove it, but I'd prefer not to, if I have the option. ClinicalCosmologist (talk) 08:06, 13 December 2017 (UTC)

  • The question seems to complain that the regexp matches the loopback IP (which I assume to be 127.0.0.1), but I fail to see why one would expect it not to be matched. By the way, for the IP matching part, it does not matter a whole lot since only "safe" inputs should be given, but the regexp looks awful - I have not tested either but you could shorten it to [0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3} (arguably easier to parse, and avoids matching empty strings for numbers e.g. 8.8..1 is a match of the current), or at least correct the first digit of each to [0-2]?[0-9]?[0-9]?\.[0-2]?[0-9]?[0-9]?\.[0-2]?[0-9]?[0-9]?\.[0-2]?[0-9]?[0-9]? since the IPv4 numbers go from 0 to 255.
I would assume the real question is why does ifconfig return the loopback address. (And the real real question is how to avoid it.) TigraanClick here to contact me 09:20, 13 December 2017 (UTC)
Thank you for this information, I've learned from that and have implemented the shorter version, it brings the IP just fine. I also added grep -Po -m1 to make sure to stop in the first match, which is the external IP. I need for a small Bash script, I prefer to avoid giving further details. Again thank you dearly for your help. ClinicalCosmologist (talk) 10:37, 13 December 2017 (UTC)
In the shorter version posted by Tigraan above, you should escape the dots, as you did in your original version, since an unescaped dot will match any character. Also, by using -m1, you are relying on ifconfig printing the external IP address first. If it happens to print the loopback address first, this won't work. It would be safer to use something like grep -Po 'inet addr:\K\d{1,3}\.\d{1,3}\.\d{1,3}.\d{1,3}' | grep -v '127\.0\.0\.1' And of course if there are multiple external addresses, all of these solutions will fail, but without knowing more about what you are doing I can't comment on how you should handle that. CodeTalker (talk) 16:02, 13 December 2017 (UTC)
Duh! Yes, of course, the dots should be escaped. (How did I even fail to do that when the exemple given did it correctly?) TigraanClick here to contact me 17:15, 13 December 2017 (UTC)

Use Microsoft Word 'manage sources' feature to automate Chicago footnotes[edit]

Hi, I'm writing a paper using Chicago style footnotes. How do I use the 'manage sources' feature to automate these? As far as I can tell, the Chicago option there will only do bracketed citations, not footnotes... Amisom (talk) 17:56, 13 December 2017 (UTC)

Bing and Google Problems?[edit]

After today's Windows 10 update, I can't seem to connect to either Google or Bing. Other websites are fine. All I get is

This site can’t provide a secure connection
www.bing.com uses an unsupported protocol.
ERR_SSL_VERSION_OR_CIPHER_MISMATCH
HIDE DETAILS
Unsupported protocol
The client and server don't support a common SSL protocol version or cipher suite.

Rojomoke (talk) 23:40, 13 December 2017 (UTC)

Resolved
A reboot and a reinstall of my anti-virus seems to have fixed things. Rojomoke (talk) 19:34, 14 December 2017 (UTC)

December 14[edit]

Computerized ordering of Chinese characters[edit]

At work yesterday I sorted a very long Excel sheet of book titles from numerous languages, and as expected, all the Chinese characters showed up together at the end. As far as I could tell without examining it closely, titles with similar characters were adjacent to each other; in particular, I marked duplicates (Conditional Formatting), and they always appeared next to each other, even though they'd not been adjacent before the sort.

How do Excel and other major English-language-developed programs sort Chinese characters? Is it typical to represent them with ASCII characters (e.g. sorting them by their binary representation), or do some such programs have a sense of stroke order? I'm talking about general-use programs, rather than software that is primarily linguistic. Nyttend (talk) 13:29, 14 December 2017 (UTC)

There are two main ways.
  • Sorting by byte order, on the encoded form of the characters. This typically works quite well within a character set, but is case sensitive, works badly between two character sets and badly between mixtures of character sets (such as accented é relative to e). It is technically easy though, robust and repeatable for a full Unicode range, even in legacy systems that are based on 8 bit ASCII encodings.
If you can achieve nothing else with a software project, make it UTF8-clean end-to-end, so that at least it doesn't break anything.
  • Collation is an important feature for any database these days, or other systems that take any sort of serious effort over text comparisons. The sophistication of the collation varies (I don't know Excel's offhand) but it begins with such simple processes as case-insensitivity, é vs e and the likely issues for European languages. Going outside Europe (or even into Cyrillic Eastern Europe) depends on vendors. Programming language support does not typically extend this far - you're looking at higher level services, like databases.[7]. Going beyond Europe into CJKV still requires care: a recent platform offering full Unicode support might work, but there are still plenty of major packages which will break here.
  • As to radical-and-stroke sorting, it's hard to even have that conversation within the software industry. Finding support for it is rare, finding a large system where such things work correctly end-to-end (where there might be products from two dozen vendors involved) is almost unheard of for software developed in Europe. Most annoyingly, it tends to stop working in European software that successfully implements it, but goes into a 'maintenance phase' (not an Agile concept) where management no longer understand or support proper i18n. It's a bit better on the US west coast, but really the main principle is always that, "If we don't use it ourselves, the ability is soon lost." Post-Brexit, some large UK suppliers are already claiming 'advantages' that this expensive internationalisation will no longer need to be supported. Andy Dingley (talk) 16:57, 14 December 2017 (UTC)
Excuse my ignorance, but is stroke order not simply (part of) a recipe for forming the glyph corresponding to a given character? I would assume that an ordering of words would be based only on the resulting character, not on the way it was produced. As such, I would assume a fixed ordering of characters, and by lexicographic extension, of words. If UTF captures that particular order is a different question, but that would only need a simple transposition table. Am I missing something? --Stephan Schulz (talk) 17:44, 14 December 2017 (UTC)
Radical-and-stroke sorting has a long tradition within Chinese and Japanese calligraphy, Four-Corner Method another fairly established history. Children learn them this way, character dictionaries are ordered this way. It's more than a simple way of ordering glyphs, such as counting descenders in Latin characters would be (possible, but with no established practice behind it).
Technically it's not even that hard to do it. What's needed is interest and commitment from the software vendors. Andy Dingley (talk) 18:02, 14 December 2017 (UTC)

Using undefined variables[edit]

If a computer program is confronted with an unknown variable, couldn't it just wait-and-see instead of raising an error?

For example, a=b+b followed by b=8 would raise a NameError in Python. But b=8 followed by a=b+b is OK. Couldn't Python just remember that the value of a is 2b and wait until it is needed as a numerical value and, if it does not get the value, then raise the error?--Hofhof (talk) 18:15, 14 December 2017 (UTC)

In procedural languages like Python the equals sign '=' means something quite different from in mathematics. It means assign the value of the right hand side to the variable on the left. The value of the variable can be changed to something quite different a few lines later. See Procedural programming. Dmcq (talk) 18:22, 14 December 2017 (UTC)
(ec) Well, it could, but it would be a rather strange thing to do, and might go against the principle of least astonishment. The statement a = b + b in Python (and its equivalent in other procedural languages) means 'calculate the current value of b + b and assign that to the variable a, not 'define a to be the whatever the value of b + b is when a is referenced. By that logic, the statements b = 8, a = b + b, b = 16, print (a) might be expected to output the value 32. AndrewWTaylor (talk) 18:25, 14 December 2017 (UTC)
Some computer languages do support this; it's called Lazy evaluation.-gadfium 18:54, 14 December 2017 (UTC)
Lazy evaluation applied more to functions, which may not be computed until the results are required. Computer algebra system may be more useful to you. Mathematica is an example of a language/system which can support statements similar to your example.-gadfium 19:03, 14 December 2017 (UTC)
Declarative programming languages do this sort of thing. In these b = 8, a = b + b, b = 16 would be wrong because b is declared twice, but a = b + b, b = 16 is okay and sets a to 32. Dmcq (talk) 23:22, 14 December 2017 (UTC)
That would be unnecessarily complicated. It is best if it knows what b is when it reaches a=b+b. Bubba73 You talkin' to me? 22:33, 14 December 2017 (UTC)
  • As noted, declarative programming (and its sometimes massive overheads) are there for this. It's not normally needed, so why support a costly feature that's not needed? In this case, a simple function definition or even a lambda would do the job far more simply (and more pythonically).
More importantly, why would you write code this way? Chances are that you didn't mean to, it was an accidental typo. In which case 'failing early' during compilation is by far the better strategy, allowing the mistake to be corrected. Maybe a is required to be 16 and a later assignment of b = 7 (and implicitly then setting a to 14 instead) would rain fiery death down upon the metropolis. Andy Dingley (talk) 23:47, 14 December 2017 (UTC)
While Python doesn't work this way, I can imagine a language that does, allowing for "spreadsheet-like" programming. A language like Prolog also finds out by itself in which order to do the evaluation.
 //Define formulas
 P=I*V; 
 R=V/I;
 //Fill the knowns
 AskAndFill("Do you know Voltage",V) 
 //etc for Power,Resistance, Current
 If R.HasValue Print("Resistance (Ohms) is " + R)

Joepnl (talk) 00:03, 15 December 2017 (UTC)

Resetting default PDF reader in Windows 10?[edit]

On my home PC, I'm running Windows 10 (professionally re-installed a week ago after an unrepairable startup error appeared). When I want to open a PDF document already downloaded, this currently defaults to using Microsoft Edge, with various alternatives also offered.

I would prefer not to use a browser program or this, but instead to use LibreOffice 5.4, which I have on the computer and which can open PDFs in its Draw application, but this is not one of the options offered.

While I can open LibreOffice Draw and then search for and open a given PDF document, I cannot figure out how to make it my .pdf default such that I can first go to the document and then open it with LibreOffice 5.4 as the default or even an alternative option.

If I go to Windows 10's

Settings, Apps, Default apps, Choose default applications by file type,

then .pdf is already set to Microsoft Edge with no way I can see to change that to anything else.

Suggestions? (Please keep things as untechnical as possible!) {The poster formerly known as 87.81.230.195} 90.220.212.173 (talk) 21:00, 14 December 2017 (UTC)

I'm not an expert on this, but if you get to settings/"Choose default apps by file type", the application extensions are listed in order on the left. Go down to "pdf", click the icon to the right. Then it should give you choices of the software you have installed. Bubba73 You talkin' to me? 22:30, 14 December 2017 (UTC)