I need the explanation of this syntax , does this mean that (+4) is the same as (4) ? I have tried many other operands and it completely works as if I disregarded the plus sign before the number .
How does Python evaluate the expression 1+++2?  How many ever + I put in between, it is printing 3 as the answer. Please can anyone explain this behavior  And for 1--2 it is printing 3 and for 1---2 it is printing -1
Is this a correct way for passing an environment variable in sudo ?  sudo -u www-data -b env FOOBAR="foobar" /home/user/folder/daemon Vertical space in lists Passing multidimensional arrays as function arguments in C In C can I pass a multidimensional array to a function as a single argument when I don't know what the dimensions of the array are going to be?  Besides, my multidimensional array may contain types other than strings. Blender 2.8 - AWS EC2 command line EEVEE render I have been trying to get this to work for a couple days now. I have an EC2 P2 instance with NVIDIA CUDA configured by default, its a Deep learning Ubuntu AMI. This OS does not have a GUI so everything is via terminal.  I downloaded Blender's 2.8 TAR file for Linux and set it up on the EC2 instance. And ran the following command from the directory where the TAR file is extracted:   ./blender -b -noaudio /home/ubuntu/file.blend --render-output . --engine BLENDER_EEVEE --render-format PNG --verbose 4   All I see in the output is this:  Blender 2.80 (sub 75) (hash f6cb5f54494e built 2019-07-29 17:17:04) found bundled python: /mnt/blender/blender-2.80-linux-glibc217-  x86_64/2.80/python Read blend: /home/ubuntu/file.blend  Blender quit   Don't know why its quitting but I am unable to debug this any further. Any help would be appreciated.  UPDATE: As per @rjg's recommendation, ran the following command:  ./blender -b -noaudio /home/ubuntu/file.blend --render-output . --engine BLENDER_EEVEE --render-format PNG -f 1 --verbose 4   Got the following error:  Blender 2.80 (sub 75) (hash f6cb5f54494e built 2019-07-29 17:17:04) found bundled python: /home/ubuntu/blender/blender-2.80-linux-glibc217-  x86_64/2.80/python Read blend: /home/ubuntu/file.blend Unable to open a display Aborted (core dumped) Average distance between two random points in a square A square with side $a$ is given. What is the average distance between two uniformly-distributed random points inside the square?  For more general "rectangle" case, see . The proof found there is fairly complex, and I am looking for a simpler proof for this special case. I expect it could be significantly simpler.  See also . Making a logic circuit with only NAND GATES? This is a  about setting up .     I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer connects to our mail server via IMAP using outlook. Email is sent and received by those computers, and some users send and receive email on their mobile phones as well.  I am using  to generate an SPF record and I'm unsure about some of the fields in the wizard, specifically:   Enter any other domains who may send or relay mail for this domain Enter any IP addresses in CIDR format for netblocks that originate or relay mail for this domain Enter any other hosts which can send or relay mail for this domain How stringent should SPF-aware MTA's treat this?   the first few questions i'm fairly certain about... hope i have given enough info. Include the option to flag posts as spam in the Low Quality queue I guess this is an additional to previous requests like  and .  But I just came across  review item, and was unable to flag it as spam.  edit: Since I posted this, the item has been removed (deleted) here is a screenshot: $T$ self-adjoint on Hilbert space $H$, $T^n=T^{n+1}$ will $T$ be an orthogonal projection operator? I have seen several answers and proofs here at MSE that a self-adjoint operator $T$ on a Hilbert space $H$ where $T^2=T$, implies $T$ being an orthogonal projection operator.   The thought struck me; what would happen if the condition $T^2=T$ is replaced by $T^3=T^2$ or instead by $T^4=T^3$ or why not more generally by $T^n=T^{n+1}$ for some $n\in\mathbb{N}$? Would this still imply $T$ to be an orthogonal projection operator?  I guess someone must have thought of this before me? In that case perhaps there is a reference in the literature for this or perhaps the proof is way simpler than I might expect? How does the Higgs mechanism work? I'm not a particle physicist, but I did manage to get through the Feynman lectures without getting too lost. Is there a way to explain how the Higgs field works, in a way that people like me might have a hope of understanding? If $n&gt;1$ is an integer, then $\sum \limits_{k=1}^n \frac1k$ is not an integer.  If you know , then you know there must be a prime $p$ between $n/2$ and $n$, so $\frac 1p$ appears in the sum, but $\frac{1}{2p}$ does not. Aside from $\frac 1p$, every other term $\frac 1k$ has $k$ divisible only by primes smaller than $p$. We can combine all those terms to get $\sum_{k=1}^n\frac 1k = \frac 1p + \frac ab$, where $b$ is not divisible by $p$. If this were an integer, then (multiplying by $b$) $\frac bp +a$ would also be an integer, which it isn't since $b$ isn't divisible by $p$.  Does anybody know an elementary proof of this which doesn't rely on Bertrand's Postulate? For a while, I was convinced I'd seen one, but now I'm starting to suspect whatever argument I saw was wrong. Which badges do not cause a notification for experienced users? How do I get an animated gif to work in WPF? What control type should I use - Image, MediaElement, etc.? Is there an easy way to change filetype association? After the upgrade to 11.10 I've had the problems that    all music-files would open with banshee, which then crashed all folders would open with konsole   The first problem I  after installation of "ubuntu tweak" "> admin > filetype Associations".. Changed back to totem.  The second was somehow not accessible this way (did not give any possibility to add commands).  I've changed the line "inode/directory=nautilus-folder-hanlder.desktop" to "inode/directory=nautilus.desktop" from "/usr/share/applications/defaults.list" and now everything works fine.  Question: More convenient ways to do that? "Friendly" terminal color names in shell scripts? I'm aware of libraries in languages such as Ruby and Javascript to make colorizing your terminal scripts easier by using color names like "red".  But is there something like this for shell scripts in Bash, or Ksh, or whatever? My Area51 account crossed 200 rep today, but still other accounts don't reflect the change in reputation. When will the changes be applied? or is there no association bonus for Area51 account? Traveling to the US with new passport, visa on the old one I have a valid B1/B2 US visa expiring about a year from now. The passport it's in expired a few years ago, and I recently got a new one.   The passport number does not match, but the national ID number, mentioned in both, does (it used to be the same as your national ID, but not anymore)  Can I travel to the US carrying both passports? Or is it asking for trouble? (I read a few years ago that it was possible, but that might have changed)  Should I just get a new visa to avoid potential complications? I have an existing trigger which converts leads into peron accounts if the company name is blank.  Trigger AutoConvert on Lead (after insert) {      LeadStatus convertStatus = [           select MasterLabel           from LeadStatus           where IsConverted = true           limit 1      ];      List&lt;Database.LeadConvert&gt; leadConverts = new List&lt;Database.LeadConvert&gt;();       for (Lead lead: Trigger.new) {           if (!lead.isConverted &amp;&amp; lead.Company == null) {                Database.LeadConvert lc = new Database.LeadConvert();                String oppName = lead.Name;                 lc.setLeadId(lead.Id);                lc.setDoNotCreateOpportunity(true);                lc.setConvertedStatus(convertStatus.MasterLabel);                 leadConverts.add(lc);           }      }       if (!leadConverts.isEmpty()) {           List&lt;Database.LeadConvertResult&gt; lcr = Database.convertLead(leadConverts);      } }   I need to also write a trigger that stops records from coming into Salesforce if that email already exisits in a contact or an account (we use person accounts).  The issue is how do I get it working with the existing trigger (I need it to run before the trigger that converts it into a person account is run).   Is there a way to combine the two or add the functionality to create the record only if the email address doesn't already exist as a contact in the org? Viruses at this period of time do not fit the current definition of life.   Much of the reasoning behind this is that we currently believe that all life must be made up of cells.  Also, many biologist/scientists say that viruses are not living because all they are is just chemicals carrying out their predefined chemistry.   Has anyone every considered the fact that cells, the supposed building blocks of life, themselves simply only carry out predefined chemical actions? All actions cells carry out are chemically driven, not consciously or spiritually driven. Cells do not make choices, they follow chemical directions present in their DNA and RNA. Viruses act very similarly, following the action transcribed in their DNA or RNA.   How can we really even draw a defined line of what life is? Is there a "nice" way to think about the quotient group $\mathbb{C} / \mathbb{Z}$?  Bonus points for $\mathbb{C}/2\mathbb{Z}$ (or even $\mathbb{C}/n\mathbb{Z}$ for $n$ an integer) and how it relates to $\mathbb{C} / \mathbb{Z}$.  By "nice" I mean something like:   $\mathbb{R}/\mathbb{Z}$ is isomorphic to the circle group via the exponential map $\theta \mapsto e^{i\theta}$, and $\mathbb{C}/\Lambda$ is a complex torus for $\Lambda$ an integer lattice (an integer lattice is a discrete subgroup of the form $\alpha\mathbb{Z} + \beta\mathbb{Z}$ where $\alpha,\beta$ are linearly independent over $\mathbb{R}$.)   Intuitively, it seems like it should be something like a circle or elliptic curve.