What I have:   char * a = "world"; char * b = "Hello";   What I need is:   char * a = "Hello World";   I need to add b before a. Is there any function that doing it?
I'm working in C, and I have to concatenate a few things.  Right now I have this:  message = strcat("TEXT ", var);  message2 = strcat(strcat("TEXT ", foo), strcat(" TEXT ", bar));   Now if you have experience in C I'm sure you realize that this gives you a segmentation fault when you try to run it. So how do I work around that?
I am looking for a correct proof of this statement: If $G$ is a group such that $G/Z(G)$ is cyclic, then $G$ is commutative.  Proof: $G/Z(G)$ is isomorphic to $\operatorname{Inn}(G)$ and is cyclic, and then for every $a$ and $b$ in $G$ the inner isomorphisms $\gamma_a$ and $\gamma_b$ satisfy $\gamma_a \gamma_b = \gamma_{ab} = \gamma_{ba} = \gamma_b \gamma_a$, and therefore for every $a,b \in G$, $ab = ba$.  Is that proof complete, or am I missing something? Thanks a lot for the help. Question: Can anyone shed some light on this formula? I can't find any information on it.  It has three corollaries that I also need to understand: What's the difference between "I love singing" and "I love to sing"? I would like to know what the difference is between "I love doing something" and "I love to do something".  For example:        “I love singing.”      and,        “I love to sing.”      When I was young, I was told that "love doing something" is right, but one day, I found Jessie J wrote "I love to sing" on her Instagram. Prove that $x^x+y^y=z^z$ doesn't have integer solutions Getting MTP enabled devices to work with Ubuntu? Since Ubuntu 13.04 storage access to external devices via MTP is supposed to work out of the box via a GVFS-MTP module.      While this question is about the Galaxy Nexus, other Android devices as well as Windows Phones and MTP enabled media players are also supported.      For troubleshooting see .     I am having quite a bit of problems getting file-transfers working over MTP with the Galaxy Nexus. I am using Kubuntu 11.10 64-bit, and this is what I have done and the results I get:   Added rule for device in /etc/udev/rules.d/51-android.rules. The rule is the following and works for adb:  SUBSYSTEMS=="usb", ATTRS{idVendor}=="04e8", ATTRS{idProduct}=="6860", MODE="0666", OWNER="leob" #Galaxy Nexus  Restarted udev (and computer just to make sure).   Adb works, and all methods for reading from the device via MTP seems to work (I have tried mounting with mtpfs, gmtp and using the mtp-tools package directly). When I try to write to the device however, nothing I have tried works.  As an example, running mtp-newfolder test_dir 0 0 gives the following output:  libmtp version: 1.1.0 Device 0 (VID=04e8 and PID=6860) is a Samsung GT-P7510/Galaxy Tab 10.1. Folder creation failed. ERROR: Could not close session!   If I run mtp-folders after a failed mtp-newfolder without re-plugging the device, I get the following output:  Attempting to connect device(s) Device 0 (VID=04e8 and PID=6860) is a Samsung GT-P7510/Galaxy Tab 10.1. PTP_ERROR_IO: failed to open session, trying again after resetting USB interface LIBMTP libusb: Attempt to reset device mtp-folders: Successfully connected Friendly name: (NULL) Error 1: Get Storage information failed. Error 2: PTP Layer error 02fe: get_all_metadata_fast(): could not get proplist of all    objects. Error 2: (Look this up in ptp.h for an explanation.) Error 2: PTP Layer error 02fe: get_handles_recursively(): could not get object handles. Error 2: (Look this up in ptp.h for an explanation.) LIBMTP_Get_Storage() : Resource temporarily unavailable OK.   Accompanied by the following in dmesg:  [ 1000.912082] usb 2-4: reset high speed USB device number 7 using ehci_hcd [ 1001.045877] usb 2-4: usbfs: process 3166 (mtp-folders) did not claim interface 0 before use   Does anyone have any idea about what to do?  EDIT:  I also tried the PTP mode. Again, reading works fine, but I cannot write anything to the device. Possible pitfalls of using this (extension method based) shorthand How long do seasons last? In the Kittens Game, how long (in real life minutes) do seasons last? What's the difference between importing and extending a class? $a^2b^2+a^2c^2+b^2c^2\leq 3$ Let $a, b, c\geq 0$ s.t.$$(a^2-a+1)(b^2-b+1)(c^2-c+1)=1$$  Show that $ a^2b^2+a^2c^2+b^2c^2\leq 3$.  My idea:  I denote $a+b+c=x$, $ab+bc+ac=y$ and $abc=z$.  Then I have $$x^2+y^2+z^2-xy-xz-yz+2z-y-x=0$$ I have to show that $$y^2-2xz\leq 3$$ I tried to prove it with the sign of trinom, but it doesn't work. Is is possible that a software issue could be causing spotty USB-C connections on 2017 MacBook Pro? I have a 2017 MacBook Pro. It has 2 USB-C ports on the left side and I use an Aukey hub to provide more ports (4 USB, 1 HDMI, 1 USB-C) and always to connect two monitors.   I connect one monitor through the hub with the HDMI port and another directly to the MBP with a USB-C adapter. Sometimes when I connect the hub to the Mac and the 2nd monitor to the Mac, it works as it should with no problem...but more than half the time I have to connect, disconnect, jiggle, jangle, switch ports, reconnect HDMI, etc. and hopefully they will both work. OFTEN, I can only get one monitor to fire up.  Is there any kind of software fix or reset that might solve this issue? Any other thoughts welcome. Thanks. I was wondering if having less than 5-10GB of free space on an SSD would affect performance. Is it specific to SSD or is it more of an operating system aspect?  For example, on an Intel X-25 G2 that has TRIM support (on Windows 7). Novel about a teleportation device and a con artist alien I read two (maybe three) books about a protagonist who communicates with an alien who provides the instructions on how to create a device to teleport. The device is flawed in that it purposefully uses more energy (much more) by taking it from the rotation of the Earth.  The main character and two others continue to fight, commit intrigue, etc. The alien then uses them to recruit other races to do the same thing. 13.04 - more than four workspace shortcuts in GNOME Flashback (No effects) I'm using GNOME Flashback (No effects) on Ubuntu 13.04 and I've got six workspaces however when entering System Settings -> Keyboard -> Shortcuts -> Navigation I only see options to address the initial four.  It used to be options up to 12 workspaces there and as I certainly don't need that much, I want to have at least enough for the amount currently active.  How can I restore or add more shotcuts specifically to navigate and move windows to workspace 5 and 6? How do you detect a network disconnection when downloading a file in java? I have a box that I have extruded to the shape I want. Then I placed a cylinder so that it intersects the box. After that I deleted the bottom faces of both the cylinder and box.  Now what I want to do is delete the portion of the cylinder that is inside the box and join the nodes so that it is one object. I have already joined the meshes so I can select points/edges/faces from either shape. It seems like the easiest way would be to just put nodes where the edges of the cylinder and box intersect and then delete the parts I don't care about. I can't find a good way to do that though.  What's the best way to accomplish what I'm trying to do? I am trying to write the Euclidean algorithm in the following way:  $A = \lfloor A \div B \rfloor \times B + (\text{remainder of}) \: A \div B $   Now is there any symbol I can use  to say "remainder of A $\div$ B"? I know that in the C programming language there is the operator % for modulus; is that a valid symbol in maths? Can I write A % B? Or is there some other way? Scroll to bottom of div? I am creating a chat using Ajax requests and I'm trying to get messages div to scroll to the bottom without much luck. I am wrapping everything in this div: #scroll {     height:400px;     overflow:scroll; }  Is there a way to keep it scrolled to the bottom by default using JS? Is there a way to keep it scrolled to the bottom after an ajax request? What is the difference between the memory usage report in System Monitor and the one by free? Enable F1-F12 keys without Fn on Lenovo Ideapad S400u Order of nested random effects in lme4 I just fit a model in lme4, and I'm wondering what the heck I fit...  I have individuals id, and each is measured pass/fail on items that can be described using two factors, f1 and f2. My theory says that id and f2 can interact. So I want to compare these models:  # f2 doesn't matter m1 &lt;- lmer(pass ~ f1 + (1|id), family="binomial")  # f2 is a fixed effect, doesn't interact with individuals m2 &lt;- lmer(pass ~ f1 + f2 + (1|id), family="binomial")  # f2 is a nested random effect, interacting with individuals m3 &lt;- lmer(pass ~ f1 + (1|f2/id), family="binomial")   First, am I right that there's a random effect of each level of f2, and each individual's level of f2 is partially pooled, depending on the number of observations for that individual?  Second, does it make sense to fit f2 as a fixed effect with random individuals nested within each level of f2? How does one write that?  Third, what's this, with f2 and id reversed in the formula? I typed it by accident, but now I want to understand it.  m3weird &lt;- lmer(pass ~ f1 + (1|id/f2), family="binomial")