Please explain the fourth line in this C code #include"studio.h" void main() { int i , j= 0, k; k = i = 2 , j; // what's meaning of int , int ? printf ( "%d", k ); }   can anyone please explain what's up with that int , int ..?
What does the comma operator , do? What does the , operator do in C?
How to choose a circle for default stream in Google Plus? How can I choose a specific circle for the default stream in Google+ ? Many extensions don't work, and are not comfortable if using another PC. Is it allowed/desirable to post code snippets? How create Redirect pattern from old to new URLs? D7: I'm going to update an articles path pattern (/articles/[node:uid] → /post/[new tokens]) but I need redirect users from old path to new one using tokens. And I don't know how to do that.  I tried using the , but it allows set only separate URL for each node; no group redirect patterns are allowed. Also the  doesn't allow to set patterns. How can I achieve this?    The problem partially solves by applying "Update url alias" option in admin/content. I do not find out how to show all selected type nodes at one page without pages, because it is terrible slow applying option page by page. Anyway, by this way, old aliases still exist, work, and don't redirect to new aliases. Reason for strange "canyons" of dust on the cooling platform I took apart my cooling platform Something like this :  And I found something like this inside :       I wonder why around the hollows are the "canyon like" structures.  PS: I also drop this platform on the floor, maybe this could be a reason ?   EDIT :  Everybody seems (except Brandon Enright answer) to ignore the word "dust" in this question. Those structures are not in the plastic itself. It is dust ON the plastic.  Proof :     Completely wiped out with my finger : Nonlinear function continuous but not bounded I would like an example of a map $f:H\rightarrow R$, where $H$ is a (infinite dimensional) Hilbert space, and $R$ is the real numbers, such that $f$ is continuous, but $f$ is not bounded on the close unit ball $\{ x\in H : \|x\| \leq 1\}$.  Actually, $H$ could be replaced by any Banach space (but not just a normed space-- that's too easy).  My motivation is that if $f$ is linear, this is impossible; but I have next to no intuition about non-linear functions.  Edit: Here's an example for $c_0$ which is even differentiable (disclaimer: I found it here: ).  Define $f:c_0\rightarrow F$ (where F is your field, real or complex) by $$ f(x) = \sum_{n=1}^\infty x_n^n \qquad (x=(x_n)). $$  You can estimate the sum by a geometric progression, so it does converge.  A bit of checking shows that f is Frechet differentible (so certainly continuous).  But $f(1,1,\cdots,1,0,\cdots)=n$ (if there are $n$ ones) so $f$ is not bounded on the closed unit ball.  What I don't immediately see is how to adapt this to $\ell^2$, say. How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression? Using .NET, how can you find the mime type of a file based on the file signature not the extension Grep: unexpected results when searching for words in heading from man page I'm running into weird behavior when trying to grep a man page on macOS. For example, the Bash man page clearly has an occurrence of the string NAME:  $ man bash | head -5 | tail -1 NAME   And if I grep for name I do get results, but if I grep for NAME I don't:  $ man bash | grep 'NAME' $ man bash | grep NAME   I've tried other uppercase words that I know are in there, and searching for SHELL yields nothing whereas searching for BASH yields results.  What's going on here?  Update: Thanks for all the answers! I thought it worth adding the context in which I ran into this. I wanted to write a bash function to wrap man and in cases where I've tried to look up the man page for a shell builtin, jump to the relevant section of the Bash man page. There might be a better way, but here's what I've got currently:  man () {   case "$(type -t "$1")" in     builtin)       local pattern="^ *$1"        if bashdoc_match "$pattern \+[-[]"; then         command man bash | less --pattern="$pattern +[-[]"       elif bashdoc_match "$pattern\b"; then         command man bash | less --pattern="$pattern[[:&gt;:]]"       else         command man bash       fi       ;;     keyword)       command man bash | less --hilite-search --pattern='^SHELL GRAMMAR$'       ;;     *)       command man "$@"       ;;   esac }  bashdoc_match() {   command man bash | col -b | grep -l "$1" &gt; /dev/null } How to do integer & float calculations, in bash or other languages/frameworks? Using echo "20+5" literally produces the text "20+5".  What command can I use to get the numeric sum, 25 in this case?  Also, what's the easiest way to do it just using bash for floating point? For example, echo $((3224/3807.0)) prints 0 :(.  I am looking for answers using either the basic command shell ('command line') itself or through using languages that are available from the command line. How to determine if the specific time is between given time range in javascript How can I select a point without selecting its reflected side What is the difference between would and will in the following examples?        How would you use this word in a sentence?     How will you use this word in a sentence? How to split a string with any whitespace chars as delimiters What regex pattern would need I to pass to  java.lang.String.split()  to split a String into an Array of substrings using all whitespace characters (' ', '\t', '\n', etc.) as delimiters? Direction of friction when a car turns When a ball moves to the right, friction acts to oppose the motion, in other words, to the left. However, when a car travels around a bend, the friction acts in the perpendicular direction to the car's velocity and provides the centripetal force. I just cannot understand why friction would act in that direction. Parsing date/time string with timezone abbreviated name in Python? Which is correct, "you and I" or "you and me"? How can I turn off "middle mouse button paste" functionality in all programs? I don't like having the middle mouse button paste, because I often end up with uncompilable code in Eclipse. How can I turn this off (in all programs)? I'm running Fedora. If $p\in\Bbb Z[X]$ show that: $ \max\limits_{x\in [0,1]}\left|p(x) \right| > \frac{1}{e^{n}}. $ This is problem 10 from the International Mathematical Competition for University Students of 2015, from day 2, in Bulgaria. I think it is an interesting problem!     Let $n$ be a positive integer, and $p(x)$ be a polynomial of degree $n$ with integer coefficients. Prove that   $$ \max_{x\in [0,1]}\left|p(x) \right| &gt; \frac{1}{e^{n}}. $$   Proposed by Géza Kós, Eötvös University, Budapest. PCA and proportion of variance explained How to find continued fraction of pi I have always been amazed by the continued fractions for $\pi$. For example some continued fractions for pi are:  $\pi=[3:7,15,1,292,.....]$ and many others given .  Similarly some nice continued fractions for $e$ and it's derivatives are given .I have tried to prove that the are indeed the continued fractions but did not get very far.If any one can can help it would be great(especially if there is some easy way to get continued fraction of derivatives of e from the original continued fraction of e).Here derivatives of e I mean $\sqrt e,\frac{e-1}{e+1} $ etc.