Question is just as the title says. Let's say a script prompts the user to input something, and stores said input into a variable. What's the easiest way to check if that user input/variable is a number in perl?
Is there a simple way in Perl that will allow me to determine if a given variable is numeric?  Something along the lines of:  if (is_number($x)) { ... }   would be ideal.  A technique that won't throw warnings when the -w switch is being used is certainly preferred.
Indefinite articles used with plural nouns: It was AN amazing TWO DAYS Show that $\mathbb{Q}\times \mathbb{Q}$ is denumerable I am new to functions and relations, and with some concepts I am not so familiar. I have a question in an homework:     Show that $\mathbb{Q} \times\mathbb{Q}$ is denumerable.   From what I understood, denumerable means that it is infinitively countable. There are some  on the web about this topic, but I am still not understanding their explanation, maybe because they are not explained so easily (for me).  From what I understood, a set is denumerable if there's a relation with the natural numbers (but I am still not understanding what is this relation).  I have heard also about equinumerous sets (contain a bijective function = onto + one-to-one function), but I cannot relate this information with the problem to try to solve it. How to make wget faster or multithreading? I've just upgraded my computer hardware(cpu + motherboard + graphic card + memory + hard disk), so that install a new OS is needed. I tried to download debian-6.0.6-amd64-netinst.iso with wget command but the speed is so slow that I could not bear. 4Kb/s ~ 17 Kb/s, slow like a running turtle, or even more slower if I use Chrome.  I've read the help information of wget, it seems like there are no options could make it more faster.  Is there anyway to make wget faster? Or is it possible to make it multi-threading download?  PS: my bandwidth is 4M. I use this command:  wget -c url  http://hammurabi.acc.umu.se/debian-cd/6.0.6/amd64/iso-cd/debian-6.0.6-amd64-netinst.iso A post here on DBA.StackExchange () has spawned an interesting question (at least, interesting to me) regarding performance in MySQL.  The context is that we want to insert a record in a table for each row that is updated.  Before the row is updated, we want to store off a previous value and then increment one of the columns (a "version" column).  If we do this inside a trigger, it works out nicely.  For MySQL, the triggers are , so it would be an easy solution.  Select the data currently in the table, insert it into the logging table, and the update the "version" column in the new data.  However, it's possible to move this logic to a stored procedure. If you do that, you're performing the insert, then incrementing the "version" column in the table.  The entire thing would be set based.   So, when it comes to performing this insert, would this be more performant to use the set-based stored procedure approach or a trigger based approach?  This question is for MySQL (since it has row-by-row triggers), although it could apply to other row-by-row trigger DBMSs. Lightning component quick action - send parameters to the lightning component I have a lightning component that is available for use as lightning component quick action. I need to use this component from various object actions, for example, I will add a lightning component quick action to account object and to contact object. Now on the lightning component itself, I want to know if it was invoked from the account object or from the contact object, but I cannot find a way to do that. I have found a way to get the record Id by adding &lt;aura:attribute name=&quot;recordId&quot; type=&quot;String&quot; /&gt; (see code snippet below) It is working but not good enough. What I really need is to send a parameter from the lightning component quick action invocation:  And get it in my component: &lt;aura:component implements=&quot;force:lightningQuickAction,force:hasRecordId,flexipage:availableForAllPageTypes&quot;&gt;     &lt;aura:attribute name=&quot;recordId&quot; type=&quot;String&quot; /&gt;     &lt;aura:attribute name=&quot;param&quot; type=&quot;String&quot;/&gt; &lt;/aura:component&gt;  Is this possible? And if not - any workaround for achieving that? When I want to move a file to the Trash, Nautilus give me an message saying this:     You can't move example.file to the trash can. Do you want to remove it immediately?   I can give you this photo but it's in Spanish Do the druid's uses of the Wild Shape feature recharge while still in Wild Shape?  Say a 10th-level Circle of the Moon Druid spends two uses of Wild Shape to transform into an Air Elemental, whose form she can stay in for the next 5 hours. After 2 hours, she takes a short rest, but does not drop the Wild Shape. She has another couple of hours to keep the Air Elemental form.  My main concern: Does she get her two uses of Wild Shape back with that short rest? Or, does she have to drop the Air Elemental form first before taking the short rest to recharge Wild Shape? I have created my StackOverflow Careers panel, and when I click 'add a stack overflow account with over 200 reputation' the site decides that I have no StackOverflow account at all, although my current one has over 300. I log in to both with the same StackExchange Account with the same email etc so I'm curious as to why this is happening. What is LookDev/Material Preview mode for in 2.8? If I have an i.i.d. random variables $X_i$ from a uniform distribution on $[0,1]$.   How would I find scaling sequences $a_n$, $b_n$ such that $a_n(M_n − b_n)$ converges in distribution to a non-trivial limit function $G$ for  $ Y_i = X_i,$ and $M_n = \max(Y_1,...,Y_n) $ Can you please check my Cesaro means proof I wanted to prove the following:  if $x_n \to x$ then $y_n \to x$ where $$ y_n = {x_1 + \dots + x_n \over n}$$  Please can you tell me if my proof is correct? My proof is this:  Let $\varepsilon &gt; 0$. Fix $N$ such that $n &gt; N$ implies $|x_n - x| &lt; {\varepsilon \over 2}$.   Then $\left |{1 \over n} \sum_{k=N+1}^{N + n} x_k - x \right | &lt; {\varepsilon \over 2}$. Now let $M$ be such that ${|x_1 + \dots + x_N | \over M} &lt; {\varepsilon \over 2}$ and $M &gt; N$. Then  $$ \left | \sum_{k=1}^M {x_k \over M} - x   \right | \le  \left | \sum_{k=1}^N {x_k \over M}   \right | +  \left | \sum_{k=N+1}^M {x_k \over |M-N|}  - x   \right | &lt; \varepsilon $$ Here the proof is finished. But one can observe:  It is possible that $y_n$ converges even if $x_n$ doesn't: If $x_{2n} = 0$ and $x_{2n + 1} = 1$ then $x_n$ does not converge but $y_n \to {1 \over 2}$. Custom Tools not Saving in Toolbar on Startup/ Normal.mxt? I am trying to save some tools that I have created into the default toolbar layout that is present when ArcMap 10.1 is launched.  It is possible to change the arrangement of toolbars, add new ones and even add in existing tools, but any custom tools I set in the commands category "geoprocessing tools" are gone and do not appear in the toolbar. How can I save these custom tools to the default layout that appears on startup?  Update:  Saving a document with the custom tools added and reopening it preserves the tools, but opening a template (10.1 mxd) containing the tools, then opening and older document will cause the tools to disappear. Oddly enough, any other changes made after the custom tools were added are preseved.  Update (03/18/2014):  I have upgraded to 10.2 and this has still not been fixed. I did not see this issue in the 10.21 changelog so I doubt it will address it. For those interested in this issue, I have started a forum post on the ESRI forums . Compress a directory using tar/gz over SSH to local computer? I'd like to essentially tar/gz a directory on a remote machine and save the file to my local computer without having to connect back into my local machine from the remote one. Is there a way to do this over SSH? The tar file doesn't need to be stored on the remote machine, only on the local machine. Is this possible? What tips and advice do you have for photographing the Aurora Borealis? A friend has been kind enough to lend me a DSLR for a few months.  It's my first foray into DSLR photography, or indeed any kind of photography beyond simply aiming my Canon IXUS at something and clicking the button.    Over the last few weeks, I've been busy studying, practising and trying to learn as much as possible ahead of a planned trip to Norway where I hope to see, and get some photos of, the Aurora Borealis.  I currently have:   Canon Rebel Xsi (450D) Canon 50mm f/1.4 L  Canon 18-55m kit lens Aluminium full height tripod with ball head Cable release Spare battery &amp; memory cards   I'm prepared to spend the night wrapped up outdoors, in the hope that they will make an appearance. I'd like some advice on how to get the most out of this kit for the trip:   How should I go about setting up to get pics of the Aurora?  How might I achieve optimum focus? From what I've read, I'll need to use the tripod and cable release, with IS turned off, on continuous shooting mode with long exposure times. But I'd like some more specific tips in terms of which aperture and ISO settings might work best? Should I use one of the lenses above, or would it be worthwhile renting a better, wide angle lens; if so, which would you recommend? How to determine $\int x^2 e^{-x^2}\mathrm dx$? Functions that are their Own nth Derivatives for Real $n$ Let $A$ be a ring with $0 \neq 1 $, which has $2^n-1$ invertible elements and less non-invertible elements. Prove that $A$ is a field. "Never say die?" What's the deal with this idiom? I know what it means, but cannot wrap my head around its grammar structure. The sentence structure of     "Never say die"   looks like that of     "Never admit defeat"   but it does not make the same grammatical+semantical sense.  Is it an archaic use? Is it a contraction of a longer phrase? Was it originally misspoken by someone of note and survived memetically? What are its roots?  Edit: Well, the comments made me realize that I worded my question poorly. I'm not saying I think this phrase is ungrammatical. I'm asking how the heck "saying 'die'" came to mean what it means. Is it possible for information (like 1 and 0s) to be transmitted faster than light?   For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them starts pulling and pushing on his/her end.   The person on the opposite end should receive the pushes and pulls instantaneously as no particle is making the full journey.  Would this actually work? Does Hard reboot damage my Ubuntu