Sorting array with null values
How to sort an array of objects containing null elements?
Let $P(X)$ denote the power set of $X$ (the set of all subsets of $X$) with a partial order given by inclusion.  If $F: P(X) \to  P(X)$ is monotone (order preserving), then $F$ has a fixed point.  How are we going to prove that without using the term (complete lattice)?! Stealing and reattaching a running process It's sunday and I left an instance of R running in the office. The script finished running, and I would like to save my workspace without going to the office. I can ssh to the computer, but I have not run the program into screen.  Is there a way, over ssh, to disown the process (I don't have access to jobsid of the terminal the program is running on!) and reattach it with say, reptyr? Reptyr and reptyr -T don't work without previously disowning the process  28845 3diag       20   0  139.3m  10.4m   0.0  0.1   0:12.06 S  `- urxvtd                                                                                        5327 3diag       20   0   16.4m   4.6m   0.0  0.1   0:00.02 S      `- bash                                                                                      5335 3diag       20   0 3499.3m 3.244g   0.0 43.3 171:57.89 S          `- R    The unique part of my question is that I explicitly require to detach a program without having access to the terminal in which it was created. Pass An Instantiated System.Type as a Type Parameter for a Generic Class No version of Ubuntu can be installed with any Skylake 6th generation Intel processor I often hear about subatomic particles having a property called "spin" but also that it doesn't actually relate to spinning about an axis like you would think. Which particles have spin? What does spin mean if not an actual spinning motion? What is the square root of complex number i? cron Vs. sleep - which is the better one in terms of efficient cpu/memory utilization? How do you specify the FQDN (Host and Domain Name) that a mail server presents itself as in HELO/EHLO when sending outgoing email with sendmail? Random point uniform on a sphere Show the two fields are not isomorphic Let $p,q,r$ be prime integers with $q\neq r$. Let $\sqrt[p]q$ denote any root of $x^p-q$ and $\sqrt[p]r$ denote any root of $x^p-r$. Please show that $\mathbb{Q}(\sqrt[p]q)\neq\mathbb{Q}(\sqrt[p]r)$.  By Eisenstein we know the two polynomials are irreducible and so they are minimal polynomials and both have degree $p$. I have seen people showing one slide progressively by pressing Enter. Could anyone tell me how to realize that in Beamer? Why are some faces in my mesh darker? Why are relays so frequently driven by optocouplers? Someone who gives unsolicited explanations in a condescending way Prove that $f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}$ under some conditions Prove that $f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}$, with $f: (k_1,k_2)\to\Bbb R$ differentiable at $a\in (k_1,k_2)$, $\lim b_n=\lim a_n=a$, and $a_n&lt;a&lt;b_n$.   My attempt: Im trying to write the above equality as a particular case of this other equality that hold by any interior point $a$  $$f'(a)=\lim_{h\to 0}\frac{f(a+h)-f(a-h)}{2h}$$  Because $a_n&lt;a&lt;b_n$ then I can write  $$f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}=\lim_{n\to\infty}\frac{f(h_n+a)-f(a-j_n)}{h_n+j_n}$$  Where $h_n=b_n-a&gt;0$ and $j_n=a-a_n&gt;0$, where these two new sequences tends monotonically to zero.  Now my problem: my thought is that $h_n$ and $j_n$ are particular sequences then I can build a sequence $k_n$ such that $j_n$ and $h_n$ are subsequences so I can write:  $$\{h_n:n\in\Bbb N\}\subset\{k_n:n\in\Bbb N\}\text{ and }\{j_n:n\in\Bbb N\}\subset\{k_n:n\in\Bbb N\}$$  (I can build this $k_n$ by example doing $k_{2n}=h_n$ and $k_{2n-1}=j_n$) and then I have the desired expression  $$f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}=\lim_{n\to\infty}\frac{f(k_n+a)-f(a-k_n)}{2k_n}$$  My question:   Is this proof right? In particular Im unsure of the implicit statement "if the limit exist for $k_n$ then it must exist too for the particular case with $h_n$ and $j_n$". The use of two sequences, $h_n$ and $j_n$ in the limit make me unsure about the validity of this manipulation and assumption. There is a simpler/different way to prove the same?   Thank you in advance. Create Task in loop but all tasks take the same parameter Laptop with no battery Should I vary input field lengths in a single page checkout form? Profile tab hyperlink should match name change How to create complex conditional clauses / queries? I've been reading the documentatoin on  and also studied the api description for  and  but I fail to create a $query with 3 -&gt;conditions:   select all between 0 and 100 but exclude 23, 48 and 97 select also 107, 123, 126 and 128   That's what I have tried so far:  $query-&gt;db_or()   -&gt;condition('my_field', array(107, 123, 126, 128), 'IN')   -&gt;condition(db_and()-&gt;condition('my_field', array(0, 100), 'BETWEEN')                       -&gt;condition('my_field', array(23, 48, 97), 'NOT IN'));   But I get the following error:  PHP Fatal error:  Call to undefined method SelectQuery::db_or() in [... first line]   I've tried to play around with the syntax like that:  $query-&gt;condition(-&gt;db_or()   -&gt;condition('my_field', array(107, 123, 126, 128), 'IN')   -&gt;condition(db_and()-&gt;condition('my_field', array(0, 100), 'BETWEEN')                       -&gt;condition('my_field', array(23, 48, 97), 'NOT IN')));   But again getting errors like that:  PHP Parse error:  syntax error, unexpected T_OBJECT_OPERATOR, expecting ')' in [... first line]   I also tried working with variables:  $cond01 = array('my_field', array(107, 123, 126, 128), 'IN'); $cond02 = array('my_field', array(0, 100), 'BETWEEN'); $cond03 = array('my_field', array(23, 48, 97), 'NOT IN'); $db_and = db_and(); $db_and-&gt;condition($cond02); $db_and-&gt;condition($cond03); $db_or = db_or(); $db_or-&gt;condition($cond01); $db_or-&gt;condition($db_and); $query-&gt;condition($db_or);   But this again yields drupal errors like that:  SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Array' in 'where clause'   How to create a complex conditional database query with both AND and OR statements?