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  • Inverse relationship of two variables

    - by Jam
    this one is maybe pretty stupid.. Or I am just exhausted or something, but I just cant seem to solve it.. Problem : two variables X and Y, value of Y is dependent on value of X. X can have values ranging from some value to some value (lets say from 0 to 250) and y can have different values (lets say from 0.1 to 1.0 or something..) - but it is inverse relatonship (what I mean is: if value of X is e.g. 250, then value of Y would be 0.1 and when X decreases up to 0, value of Y raises up to 1.0.. So how should I do it? lets say I have function: -- double computeValue (double X) { /computation/ return Y; } Also, is there some easy way to somehow make the scaling of the function not so linear? - For example when X raises, Y decreases slower at first but then more rapidly in the end.. (rly dont know how to say it but I hope you guys got it) Thanks in advance for this stupid question :/

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  • How to create updateable panel using AjaxLink of Wicket?

    - by Arne
    I try to realize a link (in fact many links) that update a table in an website using an AjaxLink of Wicket. But I fail, the table is never updated (I have "setOutputMarkupId(true)" and call "addComponent", but there must be something other thats wrong). How can I realize a panel with a number of links and a table that displays dynamic data, dependent on the link clicked? Can someone give an example (Maybe two links, when the first one is clicked the table displays two random numbers from 1-10, when the second is clicked the table displays random numbers from 1-100)? Without reloading the entire page, but only the html for the table?

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  • Linux C: "Interactive session" with separate read and write named pipes?

    - by ~sd-imi
    Hi all, I am trying to work with "Introduction to Interprocess Communication Using Named Pipes - Full-Duplex Communication Using Named Pipes", http://developers.sun.com/solaris/articles/named_pipes.html#5 ; in particular fd_server.c (included below for reference) Here is my info and compile line: :~$ cat /etc/issue Ubuntu 10.04 LTS \n \l :~$ gcc --version gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3 :~$ gcc fd_server.c -o fd_server fd_server.c creates two named pipes, one for reading and one for writing. What one can do, is: in one terminal, run the server and read (through cat) its write pipe: :~$ ./fd_server & 2/dev/null [1] 11354 :~$ cat /tmp/np2 and in another, write (using echo) to server's read pipe: :~$ echo "heeellloooo" /tmp/np1 going back to first terminal, one can see: :~$ cat /tmp/np2 HEEELLLOOOO 0[1]+ Exit 13 ./fd_server 2 /dev/null What I would like to do, is make sort of a "interactive" (or "shell"-like) session; that is, the server is run as usual, but instead of running "cat" and "echo", I'd like to use something akin to screen. What I mean by that, is that screen can be called like screen /dev/ttyS0 38400, and then it makes a sort of a interactive session, where what is typed in terminal is passed to /dev/ttyS0, and its response is written to terminal. Now, of course, I cannot use screen, because in my case the program has two separate nodes, and as far as I can tell, screen can refer to only one. How would one go about to achieve this sort of "interactive" session in this context (with two separate read/write pipes)? Thanks, Cheers! Code below: #include <stdio.h> #include <errno.h> #include <ctype.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> //#include <fullduplex.h> /* For name of the named-pipe */ #define NP1 "/tmp/np1" #define NP2 "/tmp/np2" #define MAX_BUF_SIZE 255 #include <stdlib.h> //exit #include <string.h> //strlen int main(int argc, char *argv[]) { int rdfd, wrfd, ret_val, count, numread; char buf[MAX_BUF_SIZE]; /* Create the first named - pipe */ ret_val = mkfifo(NP1, 0666); if ((ret_val == -1) && (errno != EEXIST)) { perror("Error creating the named pipe"); exit (1); } ret_val = mkfifo(NP2, 0666); if ((ret_val == -1) && (errno != EEXIST)) { perror("Error creating the named pipe"); exit (1); } /* Open the first named pipe for reading */ rdfd = open(NP1, O_RDONLY); /* Open the second named pipe for writing */ wrfd = open(NP2, O_WRONLY); /* Read from the first pipe */ numread = read(rdfd, buf, MAX_BUF_SIZE); buf[numread] = '0'; fprintf(stderr, "Full Duplex Server : Read From the pipe : %sn", buf); /* Convert to the string to upper case */ count = 0; while (count < numread) { buf[count] = toupper(buf[count]); count++; } /* * Write the converted string back to the second * pipe */ write(wrfd, buf, strlen(buf)); } Edit: Right, just to clarify - it seems I found a document discussing something very similar, it is http://en.wikibooks.org/wiki/Serial_Programming/Serial_Linux#Configuration_with_stty - a modification of the script there ("For example, the following script configures the device and starts a background process for copying all received data from the serial device to standard output...") for the above program is below: # stty raw # ( ./fd_server 2>/dev/null; )& bgPidS=$! ( cat < /tmp/np2 ; )& bgPid=$! # Read commands from user, send them to device echo $(kill -0 $bgPidS 2>/dev/null ; echo $?) while [ "$(kill -0 $bgPidS 2>/dev/null ; echo $?)" -eq "0" ] && read cmd; do # redirect debug msgs to stderr, as here we're redirected to /tmp/np1 echo "$? - $bgPidS - $bgPid" >&2 echo "$cmd" echo -e "\nproc: $(kill -0 $bgPidS 2>/dev/null ; echo $?)" >&2 done >/tmp/np1 echo OUT # Terminate background read process - if they still exist if [ "$(kill -0 $bgPid 2>/dev/null ; echo $?)" -eq "0" ] ; then kill $bgPid fi if [ "$(kill -0 $bgPidS 2>/dev/null ; echo $?)" -eq "0" ] ; then kill $bgPidS fi # stty cooked So, saving the script as say starter.sh and calling it, results with the following session: $ ./starter.sh 0 i'm typing here and pressing [enter] at end 0 - 13496 - 13497 I'M TYPING HERE AND PRESSING [ENTER] AT END 0~?.N=?(?~? ?????}????@??????~? [garble] proc: 0 OUT which is what I'd call for "interactive session" (ignoring the debug statements) - server waits for me to enter a command; it gives its output after it receives a command (and as in this case it exits after first command, so does the starter script as well). Except that, I'd like to not have buffered input, but sent character by character (meaning the above session should exit after first key press, and print out a single letter only - which is what I expected stty raw would help with, but it doesn't: it just kills reaction to both Enter and Ctrl-C :) ) I was just wandering if there already is an existing command (akin to screen in respect to serial devices, I guess) that would accept two such named pipes as arguments, and establish a "terminal" or "shell" like session through them; or would I have to use scripts as above and/or program own 'client' that will behave as a terminal..

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  • Access violation reading location 0x00184000.

    - by numerical25
    having troubles with the following line HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); it appears the CreateBuffer method is having troubles reading &mVB. mVB is defined in box.h and looks like this ID3D10Buffer* mVB; Below is the code it its entirety. this is all files that mVB is in. //Box.cpp #include "Box.h" #include "Vertex.h" #include <vector> Box::Box() : mNumVertices(0), mNumFaces(0), md3dDevice(0), mVB(0), mIB(0) { } Box::~Box() { ReleaseCOM(mVB); ReleaseCOM(mIB); } float Box::getHeight(float x, float z)const { return 0.3f*(z*sinf(0.1f*x) + x*cosf(0.1f*z)); } void Box::init(ID3D10Device* device, float m, float n, float dx) { md3dDevice = device; mNumVertices = m*n; mNumFaces = 12; float halfWidth = (n-1)*dx*0.5f; float halfDepth = (m-1)*dx*0.5f; std::vector<Vertex> vertices(mNumVertices); for(DWORD i = 0; i < m; ++i) { float z = halfDepth - (i * dx); for(DWORD j = 0; j < n; ++j) { float x = -halfWidth + (j* dx); float y = getHeight(x,z); vertices[i*n+j].pos = D3DXVECTOR3(x, y, z); if(y < -10.0f) vertices[i*n+j].color = BEACH_SAND; else if( y < 5.0f) vertices[i*n+j].color = LIGHT_YELLOW_GREEN; else if (y < 12.0f) vertices[i*n+j].color = DARK_YELLOW_GREEN; else if (y < 20.0f) vertices[i*n+j].color = DARKBROWN; else vertices[i*n+j].color = WHITE; } } D3D10_BUFFER_DESC vbd; vbd.Usage = D3D10_USAGE_IMMUTABLE; vbd.ByteWidth = sizeof(Vertex) * mNumVertices; vbd.BindFlags = D3D10_BIND_VERTEX_BUFFER; vbd.CPUAccessFlags = 0; vbd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA vinitData; vinitData.pSysMem = &vertices; HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); //create the index buffer std::vector<DWORD> indices(mNumFaces*3); // 3 indices per face int k = 0; for(DWORD i = 0; i < m-1; ++i) { for(DWORD j = 0; j < n-1; ++j) { indices[k] = i*n+j; indices[k+1] = i*n+j+1; indices[k+2] = (i*1)*n+j; indices[k+3] = (i*1)*n+j; indices[k+4] = i*n+j+1; indices[k+5] = (i*1)*n+j+1; k+= 6; } } D3D10_BUFFER_DESC ibd; ibd.Usage = D3D10_USAGE_IMMUTABLE; ibd.ByteWidth = sizeof(DWORD) * mNumFaces*3; ibd.BindFlags = D3D10_BIND_INDEX_BUFFER; ibd.CPUAccessFlags = 0; ibd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA iinitData; iinitData.pSysMem = &indices; HR(md3dDevice->CreateBuffer(&ibd, &iinitData, &mIB)); } void Box::Draw() { UINT stride = sizeof(Vertex); UINT offset = 0; md3dDevice->IASetVertexBuffers(0, 1, &mVB, &stride, &offset); md3dDevice->IASetIndexBuffer(mIB, DXGI_FORMAT_R32_UINT, 0); md3dDevice->DrawIndexed(mNumFaces*3, 0 , 0); } //Box.h #ifndef _BOX_H #define _BOX_H #include "d3dUtil.h" Box.h class Box { public: Box(); ~Box(); void init(ID3D10Device* device, float m, float n, float dx); void Draw(); float getHeight(float x, float z)const; private: DWORD mNumVertices; DWORD mNumFaces; ID3D10Device* md3dDevice; ID3D10Buffer* mVB; ID3D10Buffer* mIB; }; #endif Thanks again for the help

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • How to model dependency injection in UML ?

    - by hjo1620
    I have a Contract class. The contract is valid 1 Jan 2010 - 31 Dec 2010. It can be in state Active or Passive, depending on which date I ask the instance for it's state. ex. if I ask 4 July 2010, it's in state Active, but if I ask 1 Jan 2011, it's in state Passive. Instances are created using constructor dependency injection, i.e. they are either Active or Passive already when created, null is not allowed as a parameter for the internal state member. One initial/created vertex is drawn in UML. I have two arrows, leading out from the initial vertex, one leading to state Active and the other to state Passive. Is this a correct representation of dependency injection in UML ? This is related to http://stackoverflow.com/questions/2779922/how-model-statemachine-when-state-is-dependent-on-a-function which initiated the question on how to model DI in general, in UML.

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  • Compiler #defines for g++ and cl

    - by DHamrick
    I am writing a program that is cross platform. There are a few spots where I have to specify an operating system dependent call. #ifdef WINDOWS ..do windows only stuff #endif #ifdef LINUX ..do linux only stuff #endif Are there any preprocesser directives that get defined by the compiler so I don't have to explicitly define them when I use the command line compiler. ie. cl -DWINDOWS program.cpp or g++ -DLINUX program.cpp I realize I could easily write a makefile or have a shell/batch script that will do this automatically. But I would prefer to use the same ones as the compiler (if they exist) by default.

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  • Optimising (My)SQL Query

    - by Simon
    I usually use ORM instead of SQL and I am slightly out of touch on the different JOINs... SELECT `order_invoice`.*, `client`.*, `order_product`.*, SUM(product.cost) as net FROM `order_invoice` LEFT JOIN `client` ON order_invoice.client_id = client.client_id LEFT JOIN `order_product` ON order_invoice.invoice_id = order_product.invoice_id LEFT JOIN `product` ON order_product.product_id = product.product_id WHERE (order_invoice.date_created >= '2009-01-01') AND (order_invoice.date_created <= '2009-02-01') GROUP BY `order_invoice`.`invoice_id` The tables/ columns are logically names... it's an shop type application... the query works... it's just very very slow... I use the Zend Framework and would usually use Zend_Db_Table_Row::find(Parent|Dependent)Row(set)('TableClass') but I have to make lots of joins and I thought it'll improve performance by doing it all in one query instead of hundreds... Can I improve the above query by using more appropriate JOINs or a different implementation? Many thanks.

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  • UDF function with library dependencies on MySQL 5.1

    - by Fredrik
    I'm having a problem with a MySQL UDF function (mychem.sourceforge.net) that's dependent on a large library (openbabel.org) which is in turn plugin based. The problem is that the format plugins to openbabel doesn't seem to load in MySQL 5.1 and I suspect it might be due to the plugin_dir setting. I have set plugin_dir to /usr/lib/ which is the location for both libmychem.so and libopenbabel.so as well as the directory openbabel that contains the format plugins. Is there a way to turn off the plugin_dir restriction in MySQL (preferably without compiling MySQL from sources) so that I can test this hypothesis or do you have a different idea on what might cause the problem? All this is done on Ubuntu 10.04 (but I had the same kind of problems on 8.04, where I managed to get it working after a lot of steps that I unfortunately have forgotten...) I have turned off apparmor during testing and it doesn't help either.

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  • Writing shorter code/algorithms, is more efficient (performance)?

    - by Carlos
    After coming across the code golf trivia around the site it is obvious people try to find ways to write code and algorithms as short as the possibly can in terms of characters, lines and total size, even if that means writing something like: n=input() while n>1:n=(n/2,n*3+1)[n%2];print n So as a beginner I start to wonder whether size actually matters :D. It is obviously a very subjective question highly dependent on the actual code being used, but what is the rule of thumb in the real world. In the case that size wont matter, how come then we don't focus more on performance rather than size?

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  • How to get Drive Letter Using WMI

    - by new
    i get the vid and pid of the usb devices plugged into my system using WMI. Now i want to get the drive letter corresponding to the device vid and pid i retrievd. code hres = pSvc->ExecQuery( bstr_t("WQL"), bstr_t("SELECT * FROM Win32_USBControllerDevice"), WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &pEnumerator); if (FAILED(pclsObj->Get(L"Dependent", 0, &vtProp, 0, 0))) { cout<<"The specified property is not found."<<endl; } else { wcout <<vtProp.bstrVal << endl; } i get like below \NJ96\root\cimv2:Win32_PnPEntity.DeviceID="USB\VID_1A8D&PID_1000\35809402 0874450" how can i map DRIVE LETTER to my above output using the WMI please help me out

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  • issue with dll's embedded manifest file.

    - by satishtech
    I have created manifest file for my.dll. my.dll has a dependency on msvcr90.dll. In auto generated manifest file contains, ( i was using MS VC++ 2008 Express Edition) In side by side(winsxs) directory, there are three version on msvcr90.dll. my.dll started to using only the latest version of msvcr90.dll (9.0.30729.4148). Here in below topics i need the help: 1) my.dll is using only the latest version of msvcr90.dll . if i tried to make this dll as old. My application fails to start. How to make contidion that my.dll should refer only to the version which i mentioned in manifest file. 2) how can i tell my.dll should dependent on the msvcr90.dll which i providing in the local directory along with my.dll. I want to restrict my my.dll should not do search in the system directory for the msvcr90.dll.

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  • How to configure a OCUnit test bundle for a framework?

    - by GuidoMB
    I've been developing a Mac OS X framework and I want to use OCUnit in my XCode 3.2.1 project. I've followed several tutorials on how to configure a OCUnit test bundle. The problem is that when I create a test case that uses a function that is defined in one of the framework's sources, I get a building error telling me that the symbol is not found. I made the test bundle dependent of my project's target as the tutorial said, but that doesn't seem to be problem. First I thought that I could solve this problem by dragging the framework's source files into the compile sources section within the Test bundle target, but then all the symbols referenced from that source file started to show up in the build errors, so that seems to not be a good solution/idea. How can I configure my unit test bundle so it builds properly?

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  • Book resources for x86/x64 assembly programming on Win platform

    - by Scott Davies
    Hello, I ran a search for assembly language resources on stackoverflow.com and found some interesting results, but they seemed to boil down to two groups: 1) Assembly references to old ia32 architecture, such as the 80386 to Pentium 2) Windows agnostic books. Most of the commenters make the point that assembler is CPU dependent and that the OS is irrelevant, but it seems pointless to me to pick a book that has assembly examples that refer to MS-DOS interrupts and memory layouts. Likewise, learning assembler on Linux would seem to produce Linux executables Are there any: 1) Modern 2) x86/x64 3) on Windows platform - book resources available ? The reason I am targeting the Win platform is I would like to do low-level, OS internals programming, to supplement my Win C/C++ work. Thanks

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  • Manage duplicate jar files using ant and ivy.

    - by lawardy
    HI, I am using ant build script to build my java app and utilizing Ivy to manage its dependency. As my application is dependent/subset of other application(Main App), when running it, I set the classpath to point to lib jars of the Main App. As I tried to build the kit using ant and ivy, it includes/retrieve all the jars that is required as specified in ivy.xml The problem is, some of the jar files are duplicated with with jars file in the main app folders. Is there a way to set the classpath in build.xml to ignore retrieving jar files that already exist in the main app's lib folder. Thanks

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  • Three20 Library Cannot find its own headers Xcode iPhone

    - by DieLaughing
    import "Three20/Three20.h" Fails. Go download it and build a sample app. If that works, then make a new app from the templates provided, then watch as it fails spectacularly to find the right HEADER_SEARCH_PATH. 1) I've gone to the info page for the TARGET and not the PROJECT (Well, I tried both) and tried a bunch of different paths for the HEADER_SEARCH_PATH field. 2) I've tried dragging and dropping the dependent files from the finder and COPYING or just referencing both fails. (RANT: WTF?! Really? I wish public code libraries saved me time ONCE in my life.)

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  • C++ -malign-double compiler flag

    - by Martin
    I need some help on compiler flags in c++. I'm using a library that is a port to linux from windows, that has to be compiled with the -malign-double flag, "for Win32 compatibility". It's my understanding that this mean I absolutely have to compile my own code with this flag as well? How about other .so shared libraries, do they have be recompiled with this flag as well? If so, is there any way around this? I'm a linux newbie (and c++), so even though I tried to recompile all the libraries I'm using for my project, it was just too complicated to recursively find the source for all the libraries and the libraries they're dependent on, and recompile everything.

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  • How to make Date locale-independent?

    - by folone
    I have a db, that stores dates in OleDateTime format, in GMT timezone. I've implemented a class, extending Date in java to represent that in classic date format. But my class is locale-dependent (I'm in GMT+2). Therefore, it converts the date in the db as date - 2 hours. How do I make it convert the date correctly? I want my class to be locale-independent, always using GMT timezone. Actually, the question is: class MyOleDateTime extends Date { static { Locale.setDefault(WhatGoesHere?) } // ... some constructors // ... some methods }

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  • IF I have multiple candidate keys which one is a primary key and justify your choice ??

    - by zahrani
    Given R = { Account , Analyst , Assets, Broker, Client, Commission, Company, Dividend, Exchange, Investment, Office, Profile, Return, Risk_profile, Stock, Volume} and a set of functional dependencies F{fd1, fd2,fd3, fd4, fd5,fd6, fd7, fd8, fd9, fd10, fd11} where: fd1: Client - Office fd2: Stock - Exchange, Dividend fd3: Broker - Profile fd4: Company - Stock fd5: Client - Risk_profile, Analyst fd6: Analyst - Broker fd7: Stock, Broker - Invenstment, Volume fd8: Stock - Company fd9: Investment,Commission - Return fd10: Stock, Broker - Client fd11: Account - Assests these are candidate key(s) : (Account, Commission,Analyst ,Company) (Account, Commission,Analyst ,Stock) (Account ,Commission,Broker ,Company) (Account ,Commission,Broker ,Stock) (Account ,Commission,Client, Company) (Account ,Commission,Client ,Stock) (Q) Select a primary key and justify your choice ? I was select (Account ,Commission,Broker ,Stock) as a primary key ??? I chose that because it has the most direct dependencies compared to other ones. e.g. more attributes are functionally dependent on this primary key. please check if my answer is it true ? or Not I'm waiting your answer asap thank you

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  • Batch file writing to log then ending process

    - by Andrew Service
    I have a batch file that calls a process and in that process I have: IF %ERRORLEVEL% NEQ 0 EXIT /B %ERRORLEVEL% Now I wanted to upgrade this a bit and give some meaningful message to an output log when if the process fails, also I do not want the main batch to continue processing because the next processes are dependent on data from previous calls; I wonder if this would be correct but not sure: CALL Process 1 IF %ERRORLEVEL% NEQ 0 GOTO ErrorInfirstProcess /B %ERRORLEVEL% :ErrorInfirstProcess ECHO Process 1 Failed on %Date% at %Time%. >>C:\Log.txt" CALL Process 2 IF %ERRORLEVEL% NEQ 0 GOTO ErrorInSecondProcess /B %ERRORLEVEL% :ErrorInSecondProcess ECHO Process 2 Failed on %Date% at %Time%. >>C:\Log.txt" I also want to know if I still need the /B or do I need to put an EXIT command after the echo? Thanks A

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  • Formatting numbers by tokens with php

    - by Adam D
    I'm looking for a way to format numbers using "tokens". This needs to be conditional (for the first few leading characters). Example: <?php $styles=array('04## ### ###','0# #### ####','13# ###','1800 ### ###'); format_number(0412345678); /*should return '0412 345 678'*/ format_number(0812345678); /*should return '08 1234 5678'*/ format_number(133622); /*should return '133 622'*/ format_number(1800123456); /*should return '1800 123 456'*/ ?> Incase you haven't guessed, my use of this is to format Australian phone numbers, dependent on their 'type'. I have a PHP function that does this, but it is ~114 lines and contains a lot of repeated code. Can anyone help?

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  • Tomcat servlet-api.jar problem

    - by CitadelCSCadet
    I am running a web application using Tomcat and Java Servlets, JSP's, etc. I am aware that in order to use Servlets, it is dependent on the Servlet-api.jar file. Initially I placed this jar file in the WEB-INF/lib/ directory. This has worked fine for me for months during the developmental phase. When we put the application onto the server space we are using, we started seeing wierd problems showing up in the Catalina.out file telling us that there was dependency problems with the servlet-api.jar file. I am aware that tomcat has this jar file in its container, and that I should remove it from the WEB-INF/lib/ directory. I have tried this and it does not work. What do I have to do when I remove this jar file from the local files and allow it to depend on tomcats servlet-api.jar file.

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  • ruby on rails has_many through relationship

    - by BennyB
    Hi i'm having a little trouble with a has_many through relationship for my app and was hoping to find some help. So i've got Users & Lectures. Lectures are created by one user but then other users can then "join" the Lectures that have been created. Users have their own profile feed of the Lectures they have created & also have a feed of Lectures friends have created. This question however is not about creating a lecture but rather "Joining" a lecture that has been created already. I've created a "lecturerelationships" model & controller to handle this relationship between Lectures & the Users who have Joined (which i call "actives"). Users also then MUST "Exit" the Lecture (either by clicking "Exit" or navigating to one of the header navigation links). I'm grateful if anyone can work through some of this with me... I've got: Users.rb model Lectures.rb model Users_controller Lectures_controller then the following model lecturerelationship.rb class lecturerelationship < ActiveRecord::Base attr_accessible :active_id, :joinedlecture_id belongs_to :active, :class_name => "User" belongs_to :joinedlecture, :class_name => "Lecture" validates :active_id, :presence => true validates :joinedlecture_id, :presence => true end lecturerelationships_controller.rb class LecturerelationshipsController < ApplicationController before_filter :signed_in_user def create @lecture = Lecture.find(params[:lecturerelationship][:joinedlecture_id]) current_user.join!(@lecture) redirect_to @lecture end def destroy @lecture = Lecturerelationship.find(params[:id]).joinedlecture current_user.exit!(@user) redirect_to @user end end Lectures that have been created (by friends) show up on a users feed in the following file _activity_item.html.erb <li id="<%= activity_item.id %>"> <%= link_to gravatar_for(activity_item.user, :size => 200), activity_item.user %><br clear="all"> <%= render :partial => 'shared/join', :locals => {:activity_item => activity_item} %> <span class="title"><%= link_to activity_item.title, lecture_url(activity_item) %></span><br clear="all"> <span class="user"> Joined by <%= link_to activity_item.user.name, activity_item.user %> </span><br clear="all"> <span class="timestamp"> <%= time_ago_in_words(activity_item.created_at) %> ago. </span> <% if current_user?(activity_item.user) %> <%= link_to "delete", activity_item, :method => :delete, :confirm => "Are you sure?", :title => activity_item.content %> <% end %> </li> Then you see I link to the the 'shared/join' partial above which can be seen in the file below _join.html.erb <%= form_for(current_user.lecturerelationships.build(:joinedlecture_id => activity_item.id)) do |f| %> <div> <%= f.hidden_field :joinedlecture_id %> </div> <%= f.submit "Join", :class => "btn btn-large btn-info" %> <% end %> Some more files that might be needed: config/routes.rb SampleApp::Application.routes.draw do resources :users do member do get :following, :followers, :joined_lectures end end resources :sessions, :only => [:new, :create, :destroy] resources :lectures, :only => [:create, :destroy, :show] resources :relationships, :only => [:create, :destroy] #for users following each other resources :lecturerelationships, :only => [:create, :destroy] #users joining existing lectures So what happens is the lecture comes in my activity_feed with a Join button option at the bottom...which should create a lecturerelationship of an "active" & "joinedlecture" (which obviously are supposed to be coming from the user & lecture classes. But the error i get when i click the join button is as follows: ActiveRecord::StatementInvalid in LecturerelationshipsController#create SQLite3::ConstraintException: constraint failed: INSERT INTO "lecturerelationships" ("active_id", "created_at", "joinedlecture_id", "updated_at") VALUES (?, ?, ?, ?) Also i've included my user model (seems the error is referring to it) user.rb class User < ActiveRecord::Base attr_accessible :email, :name, :password, :password_confirmation has_secure_password has_many :lectures, :dependent => :destroy has_many :lecturerelationships, :foreign_key => "active_id", :dependent => :destroy has_many :joined_lectures, :through => :lecturerelationships, :source => :joinedlecture before_save { |user| user.email = email.downcase } before_save :create_remember_token validates :name, :presence => true, :length => { :maximum => 50 } VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i validates :email, :presence => true, :format => { :with => VALID_EMAIL_REGEX }, :uniqueness => { :case_sensitive => false } validates :password, :presence => true, :length => { :minimum => 6 } validates :password_confirmation, :presence => true def activity # This feed is for "My Activity" - basically lectures i've started Lecture.where("user_id = ?", id) end def friendactivity Lecture.from_users_followed_by(self) end # lECTURE TO USER (JOINING) RELATIONSHIPS def joined?(selected_lecture) lecturerelationships.find_by_joinedlecture_id(selected_lecture.id) end def join!(selected_lecture) lecturerelationships.create!(:joinedlecture_id => selected_lecture.id) end def exit!(selected_lecture) lecturerelationships.find_by_joinedlecture_id(selected_lecture.id).destroy end end Thanks for any and all help - i'll be on here for a while so as mentioned i'd GREATLY appreciate someone who may have the time to work through my issues with me...

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  • Removing items from lists and all references to them.

    - by LiamV
    I'm facing a situation where I have dependent objects and I would like to be able to remove an object and all references to it. Say I have an object structure like the code below, with a Branch type which references two Nodes. public class Node { // Has Some Data! } public class Branch { // Contains references to Nodes public Node NodeA public Node NodeB } public class Graph { public List<Node> Nodes; public List<Branch> Branches; } If I remove a Node from the Nodes list in the Graph class, it is still possible that one or more Branch objects still contains a reference to the removed Node, thus retaining it in memory, whereas really what I would quite like would be to set any references to the removed Node to null and let the garbage collection kick in. Other than enumerating through each Branch and checking each Node reference sequentially, are there any smart ideas on how I remove references to the Node in each Branch instance AND indeed any other class which reference the removed Node?

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  • Dynamic path in new.AjaxRequest with Rails

    - by Robbie
    Hello, I was wondering if there's anyway to get a 'dynamic path' into a .js file through Ruby on Rails. For example, I have the following: new Ajax.Request('/tokens/destroy/' + GRID_ID, {asynchronous:true, evalScripts:true, onComplete:function(request){load('26', 'table1', request.responseText)}, parameters:'token=' + dsrc.id + '&authenticity_token=' + encodeURIComponent(AUTH_TOKEN)}) The main URL is '/tokens/destroy/:id', however on my production server this app runs as a sub folder. So the URL for this ajax call needs to be '/qrpsdrail/tokens/destroy/:id' The URL this is being called from would be /grids/1 or /qrpsdrail/grids/1 I could, of course, do ../../path -- but that seems a bit hackish. It is also dependent on the routing never changing, which at this stage I can't guarantee. I'm just interested in seeing what other solutions there might be to this problem. Thanks in advance :)

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