Difference between double colon and arrow operators in PHP?
What's the difference between :: (double colon) and -> (arrow) in PHP?
How to prove positive semidefiniteness of two matrices through Schur Complement? Let matrices $X$ and $Y$ be positive semideﬁnite. Show that $X \succeq Y \succ 0$ is equivalent to $Y^{-1} \succeq X^{-1}$.   The teacher tells me that it is easy to prove via the Schur complement. But I could not get his idea. Could anyone help me and give me some intructions? Thanks in advance! Git keeps prompting me for a password How do I escape a percentage sign in T-SQL? I am developing a PHP application in which I am in need to store values bigger than 1 million, but with the flexibility of having floating points. I know the traditional float and double. I am looking to store only up to two decimal points, and will only handle operations with numbers that have 2 decimals exclusively.  I have chosen my column type of double and unsigned, but whenever I store a row with a value bigger than one million, it gets truncated to 999999.99  Why is this? I am looking for the right datatype/solution. If you could point me in the right direction, I will appreciate it a lot!  Thank you for your time in advance!  Cheers. Calculating the longest distance within polygon in QGIS I want to calculate the "diameter" of polygons in QGIS.  The "diameter" defined as the distance between the two most distant points of the polygon.  I couldn't find a fitting solution in the field calculator. Maybe you have some ideas? What is a Seaman's book, and can it really replace a passport? What is a "Seaman's book", and can it really replace a passport for some or all immigration purposes?  Even Wikipedia the all-knowing does not seem to know, although it contains many tantalizing references.  :     Seaman deserters may not have a passport but rather hold a Seaman's Book, (a national identity document issued to professional seamen that contains a record of their rank and service career).   :     Possession of one of the following documents is sufficient to demonstrate [right to abode] ...         Hong Kong Seaman's Identity Book Why can't light escape from a classical black hole? Regaining control of a group after being removed by another admin I created a Facebook group and was later removed by another admin.   How do I get my group back? checking apt-get update lock file How to fix very slow Ubuntu booting? why does files (nautilus) open a new window although there's one already open? When I click on "files" in the launcher it opens another window although the normal action is to maximize the window already open. It doesn't always do that. Is it a bug? I've encountered different usages of preposition + Home and I want to learn which of them are correct.  Some examples:     Back home   Back at home   Back to home I am using different operating systems on different machines on different locations. I am using a USB flash disk to keep my files (source codes etc.).  I am new to Mac OS X and now I realize there are lots of files created with a dot underscore ._ prefix.  Questions  Why are ._ files created?   What are their purpose?   How can I avoid them? Using the properties panel I can add, with "+"  button, only eight UV maps. Is it possible to have more than 8 of them? Picklist dependent on 2 controlling picklist I have 3 picklist in an object Test1, Test2, Test3  1. Test2 is dependent on Test1  2. Test3 is dependent on both.. Test1 and Test2    I want to have Test3 picklist showing values accordindly. i.e  if U selected Test1 = First and Test2 = SA . I should be able to see "IST,ABC and PQR" in Test 3.   Is this possible??? Countable or uncountable; family of disjoint triangles? If we say that $\mathcal{S}$ is a family of disjoint triangles on a plane, is $\mathcal{S}$ a countable or an uncountable set?  I believe that it is an uncountable set since $\mathbb{R}$ is uncountable and our triangles' corner coordinates are $\in \mathbb{R}$, but I cannot prove this formally, any tip would help. Does ClamAV Scan Windows virus? I'm new to Ubuntu.  I'm now setting up an OwnCloud server which supports ClamAV file scan.  Since most of the users connected to the server uses Windows OS, can ClamAV scan for Windows virus?  I also did some research that such as BitDefender. It clams that it scans real time, if someone upload files to the server, will BitDefender scan the file even OwnCloud doesn't support?  By the way, I heard that if I update the system frequently, I don't have to install any antivirus that scan for Linux virus. Is that right? When A and B are positively related variables, can they have opposite effect on their outcome variable C? A is positively related to B.  C is the outcome of A and B, but the effect of A on C is negative and the effect of B on C is positive.  Can this happen? For natural numbers $a$ and $b$, show that $a \Bbb Z + b \Bbb Z = \gcd(a, b)\Bbb Z $ For natural numbers $a$ and $b$, show that $a \Bbb Z + b \Bbb Z = \gcd(a, b)\Bbb Z $  I just basically said that the gcd of a and b { written as C } obviously divides aZ and bZ, therefore it can be rewritten as  CdZ + CeZ -> C[dZ + eZ] -> CZ[d+e] where Cd=a and Ce=b.   if a and b and C are natural numbers, then  so are d and e. the sum of d and e is an integer, that when multiplied by an integer produces an integer. therefore  CZ[d+e] = CZ, so aZ + bZ = GCD(a,b)Z  { Where C is the gcd(a,b) } Basic desktop actions are not available on Ubuntu 20.04