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  • Implementing callback functions in C

    - by robertjohn123
    Hi, I am a newbie to C.I am trying to implement callback function using function pointers. I am getting an error :test_callback.c:10: error: expected identifier or ‘(’ before ‘void’ when I try to compile the following program: #include<stdio.h> void (*callback) (void); void callback_proc () { printf ("Inside callback funtion\n"); } void register ((void (*callback) (void))) { printf ("Inside registration \n"); callback (); /* Calling an initial callback with function pointer */ } int main () { callback = callback_proc;/* Assigning function to the function pointer */ register (callback);/* Passing the function pointer */ return 0; } What is this error?Can anyone help?

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  • My AES encryption/decryption functions don't work with random ivecs

    - by Brendan Long
    I was bored and wrote a wrapper around openSSL to do AES encryption with less work. If I do it like this: http://pastebin.com/V1eqz4jp (ivec = 0) Everything works fine, but the default ivec is all 0's, which has some security problems. Since I'm passing the data back as a string anyway, I figured, why not generate a random ivec and stick it to the front, the take it back off when I decrypt the string? For some reason it doesn't work though. With random ivec: http://pastebin.com/MkDBFcn6 Well actually, it almost works. It seems to decrypt the middle of the string, but not the beginning or end: String is: 0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF Encrypting.. ???l%%1u???B! ?????`pN)?????[l????{?Q???2?/?H??y"?=Z?Cu????l%%1u???B! Decrypting.. String is: ?%???G*?5J?0??0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF!-e????V?5 I honestly have no idea what's going wrong. Maybe some stupid mistake, or maybe I'm missing something about AES?

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  • pass ...rest to a NetConnection call

    - by dome
    I want to pass a rest in a netconnection call, something like this: public function requestData(service : String, ...params) : void { nc.call(service, params); } this doesn't work since the call is expecting each parameter to be separated by commas, like: nc.call(service, params[0], params[1], params[2]); I've read some posts about apply, but I can't find a solution for this specific case.

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  • Opening a file in c++ by using a string array of adress

    - by muhammad-aslam
    Hello guYz plz help me out in making it possible to open the files by the adress provided in an array of strings......... a way to open file is as given below... ifstream infile; infile.open("d:\aslam.txt"); but how can i open file providing an array of string as an adress of file..... like this infile.open(arr[i]); (but its not working) plz help me.........

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  • validate constructor arguments or method parameters with annotations, and let them throw an exceptio

    - by marius
    I am validating constructor and method arguments, as I want to the software, especially the model part of it, to fail fast. As a result, constructor code often looks like this public MyModelClass(String arg1, String arg2, OtherModelClass otherModelInstance) { if(arg1 == null) { throw new IllegalArgumentsException("arg1 must not be null"); } // further validation of constraints... // actual constructor code... } Is there a way to do that with an annotation driven approach? Something like: public MyModelClass(@NotNull(raise=IllegalArgumentException.class, message="arg1 must not be null") String arg1, @NotNull(raise=IllegalArgumentException.class) String arg2, OtherModelClass otherModelInstance) { // actual constructor code... } In my eyes this would make the actual code a lot more readable. In understand that there are annotations in order to support IDE validation (like the existing @NotNull annotation). Thank you very much for your help.

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  • Visitor Pattern can be replaced with Callback functions?

    - by getit
    Is there any significant benefit to using either technique? In case there are variations, the Visitor Pattern I mean is this: http://en.wikipedia.org/wiki/Visitor_pattern And below is an example of using a delegate to achieve the same effect (at least I think it is the same) Say there is a collection of nested elements: Schools contain Departments which contain Students Instead of using the Visitor pattern to perform something on each collection item, why not use a simple callback (Action delegate in C#) Say something like this class Department { List Students; } class School { List Departments; VisitStudents(Action<Student> actionDelegate) { foreach(var dep in this.Departments) { foreach(var stu in dep.Students) { actionDelegate(stu); } } } } School A = new School(); ...//populate collections A.Visit((student)=> { ...Do Something with student... }); *EDIT Example with delegate accepting multiple params Say I wanted to pass both the student and department, I could modify the Action definition like so: Action class School { List Departments; VisitStudents(Action<Student, Department> actionDelegate, Action<Department> d2) { foreach(var dep in this.Departments) { d2(dep); //This performs a different process. //Using Visitor pattern would avoid having to keep adding new delegates. //This looks like the main benefit so far foreach(var stu in dep.Students) { actionDelegate(stu, dep); } } } }

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  • MATLAB: Automatic detection of relations between workspace variables through functions

    - by Peterstone
    Hi all, I´m trying to write a function what detect this relation between the variables I have got in the workspace: v1 - fft(v2) = 0 Where v1, v2 are variables of my workspace. Sometimes I need to know which variables have a certain numerical relation. If I have thirty, I don´t want to be looking for this relation in "manual way", just itroducing a sentence for each pair of different variables. I would like a function in which I introuce (or I modify this function every time I need it) the sentence (for instance what I wrote before) and the function show me the pair of variables a I am looking for. Does anyone know how to do it? Thank you so much!

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  • java.sql.SQLException: Parameter index out of range (3 > number of parameters, which is 2)

    - by sam
    @WebMethod(operationName = "SearchOR") public SearchOR getSearchOR (@WebParam(name = "comp") String comp, @WebParam(name = "name") String name) { //TODO write your implementation code here: SearchOR ack = null; try{ String simpleProc = "{ call getuser_info_or(?,?)}"; CallableStatement cs = con.prepareCall(simpleProc); cs.setString(1, comp); cs.setString(2, name); ResultSet rs = cs.executeQuery(); System.out.print("2"); /* int i = 0, j = 0; if (rs.last()) { i = rs.getRow(); ack = new SearchOR[i]; rs.beforeFirst(); }*/ while (rs.next()) { // ack[j] = new SearchOR(rs.getString(1), rs.getString(2)); // j++; ve.add(rs.getString(1)); ve.add(rs.getString(2)); }}catch ( Exception e) { e.printStackTrace(); System.out.print(e); } return ack; } I am getting error at portion i have made bold.It is pointing to that location.My Query is here: DELIMITER $$ DROP PROCEDURE IF EXISTS discoverdb.getuser_info_or$$ MySQL returned an empty result set (i.e. zero rows). CREATE PROCEDURE discoverdb.getuser_info_or ( IN comp VARCHAR(100), IN name VARCHAR(100), OUT Login VARCHAR(100), OUT email VARCHAR(100) ) BEGIN SELECT sLogin, sEmail INTO Login, email FROM ad_user WHERE company = comp OR sName=name; END $$ MySQL returned an empty result set (i.e. zero rows). DELIMITER ;

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  • Using callback functions for error handling in C

    - by Earlz
    Hi, I have been thinking about the difficulty incurred with C error handling.. like who actually does if(printf("hello world")==-1){exit(1);} But you break common standards by not doing such verbose, and usually useless coding. Well what if you had a wrapper around the libc? like so you could do something like.. //main... error_catchall(my_errors); printf("hello world"); //this will automatically call my_errors on an error of printf ignore=1; //this makes it so the function will return like normal and we can check error values ourself if(fopen.... //we want to know if the file opened or not and handle it ourself. } int my_errors(){ if(ignore==0){ _exit(1); //exit if we aren't handling this error by flagging ignore } return 0; //this is called when there is an error anywhere in the libc } ... I am considering making such a wrapper as I am synthesizing my own BSD licensed libc(so I already have to touch the untouchable..), but I would like to know what people think about it.. would this actually work in real life and be more useful than returning -1?

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  • Ruby: Parse, replace, and evaluate a string formula

    - by Swartz
    I'm creating a simple Ruby on Rails survey application for a friend's psychological survey project. So we have surveys, each survey has a bunch of questions, and each question has one of the options participants can choose from. Nothing exciting. One of the interesting aspects is that each answer option has a score value associated with it. And so for each survey a total score needs to be calculated based on these values. Now my idea is instead of hard-coding calculations is to allow user add a formula by which the total survey score will be calculated. Example formulas: "Q1 + Q2 + Q3" "(Q1 + Q2 + Q3) / 3" "(10 - Q1) + Q2 + (Q3 * 2)" So just basic math (with some extra parenthesis for clarity). The idea is to keep the formulas very simple such that anyone with basic math can enter them without resolving to some fancy syntax. My idea is to take any given formula and replace placeholders such as Q1, Q2, etc with the score values based on what the participant chooses. And then eval() the newly formed string. Something like this: f = "(Q1 + Q2 + Q3) / 2" # some crazy formula for this survey values = {:Q1 => 1, :Q2 => 2, :Q3 => 2} # values for substitution result = f.gsub(/(Q\d+)/) {|m| values[$1.to_sym] } # string to be eval()-ed eval(result) So my questions are: Is there a better way to do this? I'm open to any suggestions. How to handle formulas where not all placeholders were successfully replaced (e.g. one question wasn't answered)? Ex: {:Q3 = 2} wasn't in values hash? My idea is to rescue eval()... any thoughts? How to get proper result? Should be 2.5, but due to integer arithmetic, it will truncate to 2. I can't expect people who provide the correct formula (e.g. / 2.0 ) to understand this nuance. I do not expect this, but how to best protect eval() from abuse (e.g. bad formula, manipulated values coming in)? Thank you!

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  • Running a batch file with parameters in python OR F#

    - by Ramy
    I searched the site but didn't see anything quite matching what I was looking for. I created a stand alone application that uses a web service I created. To run the client I use: c:/scriptsdirecotry "run-client.bat" param1 param2 param3 param4 how would I go about coding this in python or F#. seems like it should be pretty simple but I haven't seen anything online that quite matches what i'm looking for. Thanks in advance.

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  • JavaFX - reduce() function to show how to pass functions as parameters

    - by Helper Method
    At the moment I'm writing a JavaFX guide for Java developers. In order to show how to pass a function to another funtion i adopted the reduce() function found in Effective Java: function reduce(seq: Integer[], f: function(: Integer, : Integer): Integer, init: Integer) { var result = init; for (i in seq) { result = f(i, result); } result } def nums = [1 .. 10]; println(reduce(nums, function(a: Integer, b: Integer) { a + b }, 0)); // prints 55 println(reduce(nums, function(a: Integer, b: Integer) { a * b }, 0)); // prints 3628800 Now I wonder if this example is not to hard for someone starting to learn JavaFX. The tutorial is targeted to programmers with a solid understanding of Java, yet I'm not quite sure about the usefulness of the example. Any ideas?

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  • String Vector program exits before input

    - by kylepayne
    So, I have a project that must add, delete, and print the contents of a vector... the problem is that, when run the program exits before I can type in the string to add to the vector. I commented the function that that portion is in. Thanks! #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); break; case 2: subvector(svector); break; case 3: vectorsize(svector); break; case 4: printvec(svector); break; case 5: printvec_bw(svector); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { string line; int i = 0; cout << "Enter the string please \n"; getline(cin, line); // doesn't prompt for input! vec.push_back(line); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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  • C# Event Handlers Using an Enum

    - by Jimbo
    I have a StatusChanged event that is raised by my object when its status changes - however, the application needs to carry out additional actions based on what the new status is. e.g If the new status is Disconnected, then it must update the status bar text and send an email notification. So, I wanted to create an Enum with the possible statuses (Connected, Disconnected, ReceivingData, SendingData etc.) and have that sent with the EventArgs parameter of the event when it is raised (see below) Define the object: class ModemComm { public event CommanderEventHandler ModemCommEvent; public delegate void CommanderEventHandler(object source, ModemCommEventArgs e); public void Connect() { ModemCommEvent(this, new ModemCommEventArgs ModemCommEventArgs.eModemCommEvent.Connected)); } } Define the new EventArgs parameter: public class ModemCommEventArgs : EventArgs{ public enum eModemCommEvent { Idle, Connected, Disconnected, SendingData, ReceivingData } public eModemCommEvent eventType { get; set; } public string eventMessage { get; set; } public ModemCommEventArgs(eModemCommEvent eventType, string eventMessage) { this.eventMessage = eventMessage; this.eventType = eventType; } } I then create a handler for the event in the application: ModemComm comm = new ModemComm(); comm.ModemCommEvent += OnModemCommEvent; and private void OnModemCommEvent(object source, ModemCommEventArgs e) { } The problem is, I get a 'Object reference not set to an instance of an object' error when the object attempts to raise the event. Hoping someone can explain in n00b terms why and how to fix it :)

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  • Ignore route with a specific parameter

    - by Vivien
    Hello, I have an @url.Action in which I pass a parameter to the action. When the parameter is null, I would like to just do nothing and stay on the same page. What I have done is the following: routes.MapRoute( null, "Test/View/{Id}", new { controller = "Test", action = "View" }, new { Id = @"\d+" } //id must be numerical ); routes.IgnoreRoute("Test/View/{*pathInfo}"); The action is not executed but my problem is that I get this: Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly. Requested URL: /Test/View Which I obvisouly do not want to see. Thanks for your help.

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  • RoR: Output Hash, getting correct parameters?

    - by andrewliu
    I have output something like this: #<Hashie::Mash created_time="1366008641" from=#<Hashie::Mash full_name="Cor Valen" id="22340" username="_corin"> id="4344344286" text="Look Who It Is, My Brother, My Favorite Deputy"> This was an output if I did this: <%= media.caption %> I wanted to get the text part, and I did this: <%= media.caption.text %> gets me error: undefined method `text' for nil:NilClass <%= media.caption[:text] %> gets me error: undefined method `[]' for nil:NilClass I don't get it? Thanks

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  • Javascript nested functions not returning

    - by Achintha Samindika
    I'm building a phonehap application. I'm using an web sql and everything works fine till data retival. function getItemGroups(){ var items_groups = new Array(); var db = window.openDatabase("merbokDB", "1.0", "MerbokDB", 5232394); db.transaction( function(tx){ tx.executeSql('SELECT * FROM item_groups',[], function(tx,result){ if(result.rows.length > 0){ var len = result.rows.length; for (var i=0; i<len; i++){ items_groups.push(result.rows.item(i).item_group); } console.log(items_groups.join()); } } ,errorCB); }, errorCB); return items_groups; } var myproducts = getItemGroups(); My problem was when I run the code "myproducts" variable is blank. but the I can see console.log(items_groups.join()); following line printing the values in console. Is I'm wrong in the way I returning?

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  • How to get parameter after "/" in URL in PHP

    - by Lucifer
    I need to let my users type anything at the end of my url, like this: http://mysite.com/?somethingorother or http://mysite.com/somethingorother And then I would like to get that last bit that they added to the end of the url like so: $var = $_POST['']; But I'm not sure how to go about this, and I can't find anything, because I'm not quite sure how to search for it. Any help is appreciated, thanks!

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  • Namespace constraint with generic class decleration

    - by SomeGuy
    Good afternoon people, I would like to know if (and if so how) it is possible to define a namespace as a constraint parameter in a generic class declaration. What I have is this: namespace MyProject.Models.Entities <-- Contains my classes to be persisted in db namespace MyProject.Tests.BaseTest <-- Obvious i think Now the decleration of my 'BaseTest' class looks like so; public class BaseTest<T> This BaseTest does little more (at the time of writing) than remove all entities that were added to the database during testing. So typically I will have a test class declared as: public class MyEntityRepositoryTest : BaseTest<MyEntity> What i would LIKE to do is something similar to the following: public class BaseTest<T> where T : <is of the MyProject.Models.Entities namespace> Now i am aware that it would be entirely possible to simply declare a 'BaseEntity' class from which all entities created within the MyProject.Models.Entities namespace will inherit from; public class BaseTest<T> where T : MyBaseEntity but...I dont actually need to, or want to. Plus I am using an ORM and mapping entities with inheritance, although possible, adds a layer of complexity that is not required. So, is it possible to constrain a generic class parameter to a namespace and not a specific type ? Thank you for your time.

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  • Get individual query parameters from Uri

    - by Ghostrider
    I have a uri string like: http://example.com/file?a=1&b=2&c=string%20param Is there an existing function that would convert query parameter string into a dictionary same way as ASP.NET Context.Request does it. I'm writing a console app and not a web-service so there is no Context.Request to parse the URL for me. I know that it's pretty easy to crack the query string myself but I'd rather use a FCL function is if exists.

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  • how to get $form_state outside of FAPI's functions?

    - by logii
    I'm writing a custom module and I'd like to use $form_state of the current form in another non-form api function - custom_facet_view_build(). any help is appreciated :) <?php /** * Implementation of hook_perm(). */ function custom_facet_perm() { return array( 'access foo content', 'access baz content', ); } /** * Implementation of hook_menu(). */ function custom_facet_menu() { $items['faceted-search'] = array( 'title' => 'Faceted Search', 'page callback' => 'drupal_get_form', 'access arguments' => array(), ); $items['facet-search-test'] = array( 'page callback' => 'drupal_get_form', 'page arguments' => array('custom_facet_form'), 'access callback' => TRUE, 'type' => MENU_CALLBACK, ); return $items; } /** * Form definition; ahah_helper_demo form. */ function custom_facet_form($form_state) { $form = array(); ahah_helper_register($form, $form_state); if (isset($form_state['storage']['categories'])) { $categories_default_value = $form_state['storage']['categories']["#value"]; } $form['facet_search_form'] = array( '#type' => 'fieldset', '#title' => t('Faceted Search'), '#prefix' => '<div id="billing-info-wrapper">', // This is our wrapper div. '#suffix' => '</div>', '#tree' => TRUE, // Don't forget to set #tree! ); $form['facet_search_form']['categories'] = array( '#type' => 'select', '#title' => t('Category'), '#options' => _custom_facet_taxonomy_query(1), '#multiple' => TRUE, '#default_value' => $categories_default_value, ); $form['save'] = array( '#type' => 'submit', '#value' => t('Save'), ); return $form; } /** * Validate callback for the form. */ function custom_facet_form_validate($form, &$form_state) { } /** * Submit callback for the form. */ function custom_facet_form_submit($form, &$form_state) { drupal_set_message('nothing done'); $form_state['storage']['categories'] = $form['facet_search_form']['categories']; // dpm($form_state); // There's a value returned in form_state['storage] within this function } /** * Implementation of hook_views_api(). */ function custom_facet_views_api() { return array( 'api' => 2, ); } function custom_facet_view_build(&$view) { dpm($form_state); // form_state['storage] remains NULL even though there's a value on previous submission }

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  • Are these two functions the same?

    - by Ranhiru
    There is a function in the AES algorithm, to multiply a byte by 2 in Galois Field. This is the function given in a website private static byte gfmultby02(byte b) { if (b < 0x80) return (byte)(int)(b <<1); else return (byte)( (int)(b << 1) ^ (int)(0x1b) ); } This is the function i wrote. private static byte MulGF2(byte x) { if (x < 0x80) return (byte)(x << 1); else { return (byte)((x << 1) ^ 0x1b); } } What i need to know is, given any byte whether this will perform in the same manner. Actually I am worried about the extra conversion of to int and then again to byte. So far I have tested and it looks fine. Does the extra cast to int and then to byte make a difference?

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  • Restful Path Parameters in Spring MVC 3

    - by MDK
    Is it possible to: set a URI template in the mvc:view-controller element of the *-servlet.xml file or in a controller method and then use/get that path parameter in a jsp? I understand that using @PathVariable in a controller method will give me access to the path parameter in that controller method. But how can I gain access to the path parameter in the jsp? For example, is it possible to do something like: *-servlet.xml file: <beans...> <mvc:view-controller path="/home" view-name="home"/> <mvc:view-controller path="/home/{error}" view-name="home"/> </beans> jsp file: <c:if test="${not empty param['error']}"> <span class="error">You have an error...</span> </c:if>

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