Is there a way to call "access callback" with parameters?
How should I implement hook_menu()?
How to favorite a question from Android app? I've found an interesting question when browsing Freelancers.SE. I've tried to star (favorite) the question but I couldn't find the option...  How to star a question from the Android app? How to ask great questions As programmers we are daily faced with having to get requirements, test things out, etc.  It's practically half our job to know what questions to ask, and how to ask them to get the most concise, actionable answer possible, especially from reluctant users/managers/customers/etc.  How do you ask questions that get answers? On every boot up I get this:    For about 10 seconds (or more) before the "normal" Ubuntu Gnome loading screen and the login screen comes up.  I've read some questions and a bug report about this already, but this problem was dismissed as a minor inconvenience or there were no real solutions (that worked for me). For me, this problem leads to an unacceptable slow boot compared to Ubuntu (Unity) or Windows.  Does anybody know how to fix this or is this a "feature" of Ubuntu Gnome and not a bug? Roll a 6-sided die until the total $\geq M$. Mean amount by which $M$ is exceeded? Here is the question:  You roll a fair 6-sided dice iteratively until the sum of the dice rolls is greater than or equal to M. What is the mean and standard deviation of the sum minus M when M=300?  Should I write a code to answer these kind of questions?  Please give me some hints on that. thanks! Let $trcA=0$.why $A=M+N$ where $M$ and $N$ are nilpotent matrices? I want to know if there is another way to solve the equation:  $$(x+1)^y-x^z=1$$  for positive integers $x,y,z$ greater than $1$ without using the Catalan identity. Does exist? By now I only know that $x\mid y$. Unable to run any GRASS 7 algorithms in QGIS 2.18.10 on Windows 7(64) \mathbb{Z} yields undefined control sequence error I was confused, trying to copy some files from one PC to another. I have it figured out, but the syntax is still confusing to me. This works:  scp ~/Desktop/Volenteer.png jay@server.ip:~j0h/b   which puts Volenteer.png in the folder /home/j0h/b.  However, this doesn't work:  scp ~Desktop/Volenteer.png     jay@server.ip:~j0h/b   This also fails, giving an exit status 1 file not found:  scp ~/Desktop/Volenteer.png     jay@server.ip:~/j0h/b   As does this:  scp ~Desktop/Volenteer.png     jay@server.ip:~j0h/b   So clearly, there is some difference between ~ and ~/ That difference is the presence of /   $~/ bash: /home/j0h/: Is a directory $ ~ bash: /home/j0h: Is a directory   So why in scp, does the ~ resolve to ~/ ? That is a guess, I cant verify that's what is happening.  But it seems inconsistent, and therefore confusing.  Is this a bug in scp? or is there something about tilde I am missing? How to nest code within a list using Markdown $A,B,C$ are three $n\times n$ matrices such that $A$ has $n$ distinct eigenvalues, $AB=BA$, and $AC=CA$.   We need to show $BC=CB$.  Let $A$ be diagonalizable with eigenvectors say, $v_1,\dots,v_n$, so there exists $P$ such that $PAP^{-1}=D$. What more I can say from the information? Please help. Trying to install ubuntu on a laptop. The "bios/uefi" has no uefi boot options &amp; the windows boot manager just kicks in. The only "option" is "boot from hard disk". So we tried to use efibootmgr to put grub to boot first.  When we run an efibootmgr -o xxxx,xxxx,xxxx command it seems like the order gets fixed but on reboot the windows boot manager still has control, then when we re-opened the live usb &amp; checked the boot order it remains unaffected.  What are other ways to change the efi boot order? Maybe by mounting the efi partition (in mnt) and doing what? The Quotation Mark character in TeXworks editor has vanished Now, my version of TeXworks is 0.4.5r.1280 and I can't have the " character on the keyboard.    I have ``  or '' instead. Why?  And It's the same with Alt+034. I'm very disappointed with that. List partition labels from the command line Is there a command that will list all partitions along with their labels? sudo fdisk -l and sudo parted -l don't show labels by default.  EDIT: (as per comment below) I'm talking about ext2 labels - those that you can set in gparted upon partitioning.  EDIT2: The intent is to list unmounted partitions (so I know which one to mount). Collection of clopen sets form a base for a countable completely regular space I have $X$ as a countable, Tychonoff space, and I want to show that the collection of clopen subset of $X$ form a base for the topology on $X$.  Can I first just define a base $\mathscr{B}$ of X, let $x\in X$ and $E \subset X$ is closed such that $x\notin E$. So $x\in X-E$, which is open.   I also noticed that the interval $[0,1]$ is uncountable. Can I define a function $f: X\to [0,1]$, then f is onto. Do I need to show that $f$ continuous next? Why crontab scripts are not working? Often, crontab scripts are not executed on schedule or as expected. There are numerous reasons for that:   wrong crontab notation permissions problem environment variables   This community wiki aims to aggregate the top reasons for crontab scripts not being executed as expected. Write each reason in a separate answer.  Please include one reason per answer - details about why it's not executed - and fix(es) for that one reason.  Please write only cron-specific issues, e.g. commands that execute as expected from the shell but execute erroneously by cron. What is the equation for the scale factor of the universe, a(t), for the best fit of data to the $\Lambda CDM$ Model of Cosmology? Ideally I like a single formula or multiple formulas for different time ranges that would cover the time from the end of inflation through 100+ billion years after the big bang using  the $\Lambda CDM$ Model.  I know that from the end of inflation back to the time of the big bang would be much more speculative, but some wild estimate would be appreciated for that time range also!  The Friedmann–Lemaître–Robertson–Walker metric defines the scale factor, a(t), from the metric: $$-c^2d\tau^2 = -c^2dt^2+a(t)^2d\Sigma^2$$ where $d\Sigma^2$ ranges over the 3 dimensional space of the universe and does not depend on time. Usually the scale of the scale factor is set by defining  $a(t_{now}) = a(13.78 B yr) \equiv 1$ Let $U,W$ be subspaces of a vector space $V$. Show that   $$\dim(U)+\dim(W)=\dim(U+W)+\dim(U\cap W)$$   Hint: Show that the map given by $L:U×W\to V$ given by $L(u,w)=u-w$ is linear.   I can show that $L:U×W\to V$ given by $L(u,w)=u-w$ is a linear map. I also know that the dimension of $U×W$ is $\dim(U)+\dim(W)$. What do I do next? Any hints? If you hash a string using SHA-256 on your computer, and I hash the same string using SHA-256 on my computer, will we generate the same value? Does the algorithm depend on a seed (so we'd both need the same seed) or some other such parameter?  edit:  To clarify, by 'string' I meant 'the same byte input', which as the comments and @ispiro's answer point out, may be different for the same character string depending on the encoding. What approach should I take to establish this logical proof? I need to design a logical math proof:  Write a detailed structured proof to prove that if m and n are integers, then either 4 divides mn or else 4 does not divide n.   Hint: Think about the form of the statement.   I was thinking about first proving that either 4 should divide m or n in order for the first part to be true, then use proof by cases to prove what happened when m was 4, and another case when n was 4...  But I got stuck, what do you recommend:    This is what I got so far: Claim: (m ∈ Z ∧ n ∈ Z) => (4 | mn ˅ 4 ∤ n)  Negated claim: (m ∈ z ∧ n ∈ z) ∧ ( P(n) ∧ ¬P(mn) )  Proof by contradiction  Assume m , n ∈ z:    Assume P(n) ∧ ¬P(mn):       Then ∃ q ∈ R, n = 4q       Let q0 be such that n = 4q0       Then mn = m(4q0)       Then mn = 4(mq0)       Then ∃ q ∈ R, mn = 4q        Then 4 | mn     Then P(n) ∧ P(mn) Then (m , n ∈ z) ∧ P(n) ∧ P(mn))    I know that is wrong, how can I fix it?