Story Identification: movie with an algae like creature in a pond
Can you identifiy this short about teenagers on a raft getting swallowed up by an oil slick?
Prove that $\frac{ 5^{125}-1}{ 5^{25}-1}$ is a composite number I'm currently working on the following problem for my computer theory class. It goes as follows:     Let $A$ and $B$ be regular expressions. Show then that $A^*B$ is the solution   of $X = AX + B$   Am I supposed to let $X = A^*B$? If so then   $A^*B = A(A^*B) + B$  I can understand that  $A(A^*B)$ could be reduced to $A^*B$ but what happens with the "${}+ B$" part of the expression? I've read up on Kleene algebra and found an axiom that seems relevant in which      $b + ax ≤ x → a^∗b ≤ x$   but I'm not actually sure if it applies. Fedora 14 uses vi by default when one runs visudo. Is there a way to change this to something else? How to quickly send commands to nested tmux sessions? I have the following in my .tmux.conf  set -g prefix M-j bind-key j  send-prefix   I need to press (Atl+J) + (J) + bound-key to send something to the nested tmux session. I feel it is rather slow. Is there any better way? For example, I would love to be able to do (Alt+J) + (2x bound-key) to do stuff in the nested session. I constantly execute commands in the top tmux session instead of executing them in the nested one. Also, how come everybody binds prefix to C-a? I find it awfully slow and unpleasant to type this combination. Am I missing something? Changing Vim indentation behavior by file type Could someone explain to me in simple terms the easiest way to change the indentation behavior of Vim based on the file type? For instance, if I open a Python file it should indent with 2 spaces, but if I open a Powershell script it should use 4 spaces. What's the easiest way to download all albums from Google Photos? I have around 950 albums at Google Photos.      I want to back them up now, but organised by albums, not by date.   Whenever I create a backup from within Google Photos, the backup splits my photos by date and adds metadata here and there.  What I am doing now is to click on every album, and choose "Download all". But this will take me ages.  Is there a way through Google Drive or another app to have a easier job? My storage was not updated I just changed my storage plan for 50 GB for $0.99 per month. When i went on settings>General>Storage and icloud usage, where it said storage above it i didnt have more storage. But the second box, where it said icloud abov it had upgraded to 50 GB. But i dont have any more storage for me to be able to get more apps etc. Short story with aliens who hear their own thoughts as god-like voices I would have read this about 20-25 years ago.  I believe the subject was an alien individual, but it could have been a non-standard human instead.  The hook of the story was that the subject lacked an organ like the  that allows the halves of the brain to communicate efficiently, allowing the illusion of a single consciousness.  The subject is conscious, and has thoughts, but is subject to hearing commands like "Wash your hands!" "Fetch water!" within its head.  I recall the subject (and others like the subject) believing that the voices are their gods talking to them.  To the reader it becomes clear that this is a separate part of the subject's own mind that is responsible for long-term planning and simply can't communicate with the rest of the mind in the way a "normal" human is accustomed to. Simulate INSERT key in Mac OS X Long story short, I am using Citrix to remote into my PC at work, and several applications require the use of the INSERT key, which, as everyone knows, Apple chose to eliminate from their keyboards. I've tried everything I can think of, and never been able to find an easy way to send this keycode via Citrix.  I'm sure there are other uses for this, and I've read quite a few people's questions on the subject, but no one seems to have offered a viable solution.  I have the Apple USB keyboard (full-size, with numeric keypad), and in the position where the INSERT key would normally exist, Apple placed the "fn" key. Now, I still need this key from time to time, but what I'd love to see is perhaps Control-fn or similar to send the keycode for INSERT.  If anyone knows how to achieve this, preferably without installing 3rd-party software (adware?), I'm all ears. Rocket Altitude Calculation Assignment Basic data I was launching a rocket model and I tried to calculate the reached altitude.  The engine (C6-0) impulse is 10 Ns Total weight is 65,7 g (includes the engine)  I calculated speed = 152 m/s $$\vec F \cdot t = \Delta m \vec v$$ Then I calculated the altitude 1007 m which seems too much to me. I guess something about 200 m (you may see the video) $$y_{\max} = \frac{v_0^2 \ }{2 g}$$ Drag I guess, I have to consider drag  Diameter of rocket 2,5 cm Drag coefficient 0,05 (I guess)  $$F_D\, =\, \tfrac12\, \rho\, v^2\, C_D\, A$$ But what about now, what is really achieved altitude? Engine description  (source: )  (source: ) Rocket Altitude Calculation Carry over long sequence of missing values with Postgres I have a table like this:  create table foo (foo_label text, foo_price int, foo_date date);  insert into foo (           values           ('aaa', 100,  '2017-01-01'),           ('aaa', NULL, '2017-02-01'),           ('aaa', NULL, '2017-03-01'),           ('aaa', NULL, '2017-04-01'),           ('aaa', 140,  '2017-05-01'),           ('aaa', NULL, '2017-06-01'),           ('aaa', 180,  '2017-07-01')         );   As you can see a few values on the foo_price column are missing.  What I need is that missing values get filled up with the "previous" available value in this way:   foo_label | fixed_foo_price | foo_date -----------+-----------------+------------  aaa       | 100             | 2017-01-01  aaa       | 100             | 2017-02-01  aaa       | 100             | 2017-03-01  aaa       | 100             | 2017-04-01  aaa       | 140             | 2017-05-01  aaa       | 140             | 2017-06-01  aaa       | 180             | 2017-07-01   My attempt:  select      foo_label,      (case when foo_price is null then previous_foo_price else foo_price end) as fixed_foo_price,     foo_date from (   select        foo_label,        lag(foo_price) OVER (PARTITION BY foo_label order by foo_date::date) as previous_foo_price,        foo_price,       foo_date       from foo ) T;   As you can see from here:    It doesn't fill completely the '100' series.  Any idea how can I get the wanted result? Best practice for typesetting quantifiers? When I work with quantifiers I noted that are very close to the other symbols and the result does not look good, for example  $\exists a\in\mathbb{R}\exists b\in\mathbb{R}\forall c\in\mathbb{R}\forall d\in\mathbb{R}$   Which is the proper form to write quantifiers? What's the difference between the work function and ionisation energy? I would like to change a file extension from *.txt to *.text. I tried using the basename command, but I'm having trouble on changing more than one file.  Here's my code:  files=`ls -1 *.txt`  for x in $files do     mv $x "`basename $files .txt`.text" done   I'm getting this error:  basename: too many arguments Try basename --help' for more information I am posting this question just to get a better understanding of the questions that can be asked on Stack Overflow.  I find that  can several answers based on users opinion and cause a discussion.  Why is this a good question when several other requests for books and tutorials are not acceptable? How can I require a generic parameter to be an enum that implements an interface? Distribution of the ratio of two i.i.d standard normals I am reading an article in which the author states that given two i.i.d random variables $X,Y\sim\mathcal{N}(0,1)$, we have $\mathbb{P}(\frac{X}{Y}\le t)=\mathbb{P}(\frac{X}{|Y|}\le t)$ since the random varaibles $\frac{X}{Y}$ and $\frac{X}{|Y|}$ are identically distributed by the symmetry of the standard normal distribution.  But I don't really understand why the random variables $\frac{X}{Y}$ and $\frac{X}{|Y|}$ are identically distributed. Can you provide a reason for why these two random variables are identically distributed? A matrix $M$ that commutes with any matrix is of the form $M=\alpha I$ how to make a 360 video (turntable) of an Object using a python script Understanding imaginary exponents