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• Glassfish: Storing Java classes in the docroot folder?

  - by Tom Marthenal

  I'm very new to using Glassfish or JSP. I have this working in NetBeans (which has Glassfish bundled) but when I try to put it on my server which is running Glassfish Server, I really don't know what I'm doing. I can place a JSP file in "domains/domain1/docroot/index.jsp" and it will work when I visit my site, but I can't, for some reason, get Java classes to work. I copied the files in "/build/web/" from the NetBeans project to the docroot folder on my server. The errors I get when I visit the site are: org.apache.jasper.JasperException: PWC6033: Error in Javac compilation for JSP PWC6199: Generated servlet error: string:///index_jsp.java:7: package test does not exist PWC6197: An error occurred at line: 5 in the jsp file: /index.jsp PWC6199: Generated servlet error: string:///index_jsp.java:52: cannot find symbol symbol : class TestClass location: class org.apache.jsp.index_jsp PWC6197: An error occurred at line: 5 in the jsp file: /index.jsp PWC6199: Generated servlet error: string:///index_jsp.java:52: cannot find symbol symbol : class TestClass location: class org.apache.jsp.index_jsp The actual Java class is in "WEB-INF/classes/test/TestClass.class" (it is pre-compiled). I really have no idea what I'm doing wrong so any help is greatly appreciated. Thanks!

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• C++ socket protocol design issue (ring inclusion)

  - by Martin Lauridsen

  So I have these two classes, mpqs_client and client_protocol. The mpqs_client class handles a Boost socket connection to a server (sending and receiving messages with some specific format. Upon receiving a message, it calls a static method, parse_message(..), in the class client_protocol, and this method should analyse the message received and perform some corresponding action. Given some specific input, the parse_message method needs to send some data back to the server. As mentioned, this happens through the class mpqs_client. So I could, from mpqs_client, pass "this" to parse_message(..) in client_protocol. However, this leads to a two-way association relationship between the two classes. Something which I reckon is not desireable. Also, to implement this, I would need to include the other in each one, and this gives me a terrible pain. I am thinking this is more of a design issue. What is the best solution here? Code is posted below. Class mpqs_client: #include "mpqs_client.h" mpqs_client::mpqs_client(boost::asio::io_service& io_service, tcp::resolver::iterator endpoint_iterator) : io_service_(io_service), socket_(io_service) { ... } ... void mpqs_client::write(const network_message& msg) { io_service_.post(boost::bind(&mpqs_client::do_write, this, msg)); } Class client_protocol: #include "../network_message.hpp" #include "../protocol_consts.h" class client_protocol { public: static void parse_message(network_message& msg, mpqs_sieve **instance_, mpqs_client &client_) { ... switch (type) { case MPQS_DATA: ... break; case POLYNOMIAL_DATA: ... break; default: break; } }

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• Howcome some C++ functions with unspecified linkage build with C linkage?

  - by christoffer

  This is something that makes me fairly perplexed. I have a C++ file that implements a set of functions, and a header file that defines prototypes for them. When building with Visual Studio or MingW-gcc, I get linking errors on two of the functions, and adding an 'extern "C"' qualifier resolved the error. How is this possible? Header file, "some_header.h": // Definition of struct DEMO_GLOBAL_DATA omitted DWORD WINAPI ThreadFunction(LPVOID lpData); void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen); void CheckValid(DEMO_GLOBAL_DATA *pData); int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName); void HandleEnd(DEMO_GLOBAL_DATA *pData); C++ file, "some_implementation.cpp" #include "some_header.h" DWORD WINAPI ThreadFunction(LPVOID lpData) { /* omitted */ } void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen) { /* omitted */ } void CheckValid(DEMO_GLOBAL_DATA *pData) { /* omitted */ } int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName) { /* omitted */ } void HandleEnd(DEMO_GLOBAL_DATA *pData) { /* omitted */ } The implementations compile without warnings, but when linking with the UI code that calls these, I get a normal error LNK2001: unresolved external symbol "int __cdecl HandleStart(struct _DEMO_GLOBAL_DATA *, wchar_t *) error LNK2001: unresolved external symbol "void __cdecl CheckValid(struct _DEMO_MAIN_GLOBAL_DATA * What really confuses me, now, is that only these two functions (HandleStart and CheckValid) seems to be built with C linkage. Explicitly adding "extern 'C'" declarations for only these two resolved the linking error, and the application builds and runs. Adding "extern 'C'" on some other function, such as HandleEnd, introduces a new linking error, so that one is obviously compiled correctly. The implementation file is never modified in any of this, only the prototypes.

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• pointer to a structure in a nested structure

  - by dpka6

  I have a 6 levels of nested structures. I am having problem with last three levels. The program compiles fine but when I run it crashes with Segmentation fault. There is some problem in assignment is what I feel. Kindly point out the error. typedef struct { char addr[6]; int32_t rs; uint16_t ch; uint8_t ap; } C; typedef struct { C *ap_info; } B; typedef struct { union { B wi; } u; } A; function1(char addr , int32_t rs, uint16_t ch, uint8_t ap){ A la; la.u.wi.ap_info->addr[6] = addr; la.u.wi.ap_info->rs = rs; la.u.wi.ap_info->ch = ch; la.u.wi.ap_info->ap = ap; }

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• What's the cleanest way to do byte-level manipulation?

  - by Jurily

  I have the following C struct from the source code of a server, and many similar: // preprocessing magic: 1-byte alignment typedef struct AUTH_LOGON_CHALLENGE_C { // 4 byte header uint8 cmd; uint8 error; uint16 size; // 30 bytes uint8 gamename[4]; uint8 version1; uint8 version2; uint8 version3; uint16 build; uint8 platform[4]; uint8 os[4]; uint8 country[4]; uint32 timezone_bias; uint32 ip; uint8 I_len; // I_len bytes uint8 I[1]; } sAuthLogonChallenge_C; // usage (the actual code that will read my packets): sAuthLogonChallenge_C *ch = (sAuthLogonChallenge_C*)&buf[0]; // where buf is a raw byte array These are TCP packets, and I need to implement something that emits and reads them in C#. What's the cleanest way to do this? My current approach involves [StructLayout(LayoutKind.Sequential, Pack = 1)] unsafe struct foo { ... } and a lot of fixed statements to read and write it, but it feels really clunky, and since the packet itself is not fixed length, I don't feel comfortable using it. Also, it's a lot of work. However, it does describe the data structure nicely, and the protocol may change over time, so this may be ideal for maintenance. What are my options? Would it be easier to just write it in C++ and use some .NET magic to use that?

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• What's the correct terminology for something that isn't quite classification nor regression?

  - by TC

  Let's say that I have a problem that is basicly classification. That is, given some input and a number of possible output classes, find the correct class for the given input. Neural networks and decision trees are some of the algorithms that may be used to solve such problems. These algorithms typically only emit a single result however: the resulting classification. Now what if I weren't only interested in one classification, but in the posterior probabilities that the input belongs to each of the classes. I.E., instead of the answer "This input belongs in class A", I want the answer "This input belongs to class A with 80%, class B with 15% and class C with 5%". My question is not on how to obtain these posterior probabilities, but rather on the correct terminology to describe the process of finding them. You could call it regression, since we are now trying to estimate a number of real valued numbers, but I am not quite sure if that's right. I feel it's not exactly classification either, it's something in between the two. Is there a word that describes the process of finding the class conditional posterior probabilities that some input belongs in each of the possible output classes? P.S. I'm not exactly sure if this question is enough of a programming question, but since it's about machine learning and machine learning generally involves a decent amount of programming, let's give it a shot.

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• How can variadic char template arguments from user defined literals be converted back into numeric types?

  - by Pubby

  This question is being asked because of this one. C++11 allows you to define literals like this for numeric literals: template<char...> OutputType operator "" _suffix(); Which means that 503_suffix would become <'5','0','3'> This is nice, although it isn't very useful in the form it's in. How can I transform this back into a numeric type? This would turn <'5','0','3'> into a constexpr 503. Additionally, it must also work on floating point literals. <'5','.','3> would turn into int 5 or float 5.3 A partial solution was found in the previous question, but it doesn't work on non-integers: template <typename t> constexpr t pow(t base, int exp) { return (exp > 0) ? base * pow(base, exp-1) : 1; }; template <char...> struct literal; template <> struct literal<> { static const unsigned int to_int = 0; }; template <char c, char ...cv> struct literal<c, cv...> { static const unsigned int to_int = (c - '0') * pow(10, sizeof...(cv)) + literal<cv...>::to_int; }; // use: literal<...>::to_int // literal<'1','.','5'>::to_int doesn't work // literal<'1','.','5'>::to_float not implemented

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• Return lines in input code causing gaps/whitespace between elements in output?

  - by Jenny Zhang

  I am trying to put images next to each other on a webpage. Here is my HTML: <img class="pt" src="Yellow Tulip.jpg" title="Yellow Tulip" alt="Yellow Tulip" /> <img class="pt" src="Pink Tulip.jpg" title="Pink Tulip" alt="Pink Tulip" /> <img class="pt" src="Purple Tulip.jpg" title="Purple Tulip" alt="Purple Tulip" /> However, on my webpage, this shows a gap between each image. I've noticed that once I remove the return line that makes the elements separate and readable and instead just put all the elements on one line, the gaps go away. <img class="pt" src="Yellow Tulip.jpg" title="Yellow Tulip" alt="Yellow Tulip" /><img class="pt" src="Pink Tulip.jpg" title="Pink Tulip" alt="Pink Tulip" /><img class="pt" src="Purple Tulip.jpg" title="Purple Tulip" alt="Purple Tulip" /> Is there anyway I can achieve the output of the latter but still have the code/input look like the former? I really like the readability that the return lines (enter spaces) bring to the code, but I don't want the whitespace it creates on the actual page. If someone could explain why this is and/or how to fix it, I'd be really grateful! :)

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• How do I structure my tests with Python unittest module?

  - by persepolis

  I'm trying to build a test framework for automated webtesting in selenium and unittest, and I want to structure my tests into distinct scripts. So I've organised it as following: base.py - This will contain, for now, the base selenium test case class for setting up a session. import unittest from selenium import webdriver # Base Selenium Test class from which all test cases inherit. class BaseSeleniumTest(unittest.TestCase): def setUp(self): self.browser = webdriver.Firefox() def tearDown(self): self.browser.close() main.py - I want this to be the overall test suite from which all the individual tests are run. import unittest import test_example if __name__ == "__main__": SeTestSuite = test_example.TitleSpelling() unittest.TextTestRunner(verbosity=2).run(SeTestSuite) test_example.py - An example test case, it might be nice to make these run on their own too. from base import BaseSeleniumTest # Test the spelling of the title class TitleSpelling(BaseSeleniumTest): def test_a(self): self.assertTrue(False) def test_b(self): self.assertTrue(True) The problem is that when I run main.py I get the following error: Traceback (most recent call last): File "H:\Python\testframework\main.py", line 5, in <module> SeTestSuite = test_example.TitleSpelling() File "C:\Python27\lib\unittest\case.py", line 191, in __init__ (self.__class__, methodName)) ValueError: no such test method in <class 'test_example.TitleSpelling'>: runTest I suspect this is due to the very special way in which unittest runs and I must have missed a trick on how the docs expect me to structure my tests. Any pointers?

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• Can this code cause a memory leak (Arduino)

  - by tbraun89

  I have a arduino project and I created this struct: struct Project { boolean status; String name; struct Project* nextProject; }; In my application I parse some data and create Project objects. To have them in a list there is a pointer to the nextProject in each Project object expect the last. This is the code where I add new projects: void RssParser::addProject(boolean tempProjectStatus, String tempData) { if (!startProject) { startProject = true; firstProject.status = tempProjectStatus; firstProject.name = tempData; firstProject.nextProject = NULL; ptrToLastProject = &firstProject; } else { ptrToLastProject->nextProject = new Project(); ptrToLastProject->nextProject->status = tempProjectStatus; ptrToLastProject->nextProject->name = tempData; ptrToLastProject->nextProject->nextProject = NULL; ptrToLastProject = ptrToLastProject->nextProject; } } firstProject is an private instance variable and defined in the header file like this: Project firstProject; So if there actually no project was added, I use firstProject, to add a new one, if firstProject is set I use the nextProject pointer. Also I have a reset() method that deletes the pointer to the projects: void RssParser::reset() { delete ptrToLastProject; delete firstProject.nextProject; startProject = false; } After each parsing run I call reset() the problem is that the memory used is not released. If I comment out the addProject method there are no issues with my memory. Someone can tell me what could cause the memory leak?

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• There is a Default instance of form in VB.Net but not in C#, WHY?

  - by Shekhar_Pro

  I'm just curious to know that there is The (Name) property, which represents the name of the Form class.This property is used within the namespace to uniquely identify the class that the Form is an instance of and, in the case of Visual Basic, is used to access the default instance of the form. Now where this Default Instance come from, why can't C# have a equivalent method to this. Also for example to show a form in C# we do something like this: //Only method Form1 frm = new Form1(); frm.Show(); But in VB.Net we have both ways to do it: //'First common method (used slash because editor wouldn't format it properly) Form1.Show(); //'Second method Dim frm as New Form1(); frm.Show(); My question comes from this first method. What is this Form1, is it an instance of Form1 or the Form1 class itself. Now as i mentioned above the Form name is the Default instance in VB.Net. But we also know that Form1 is a class defined in Designer so how can the names be same for both the Instance and class name. If Form1 is Class then there is no (Static\Shared) method named Show(). So where does this method come from. And finally why C# can't have an equivalent of this. If there some mistake in my question Please let me know *I've checked this on stackoverflow, but couldn't find an answer to this.If you do find then please give a link to it.*

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• C# 3 dimensional array definition issue

  - by George2

  Hello everyone, My following code has compile error, Error 1 Cannot implicitly convert type 'TestArray1.Foo[,,*]' to 'TestArray1.Foo[][][]' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 30 TestArray1 Does anyone have any ideas? Here is my whole code, I am using VSTS 2008 + Vista 64-bit. namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1, 1, 1]; return; } } } EDIT: version 2. I have another version of code, but still has compile error. Any ideas? Error 1 Invalid rank specifier: expected ',' or ']' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 41 TestArray1 Error 2 Invalid rank specifier: expected ',' or ']' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 44 TestArray1 namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1][1][1]; return; } } } EDIT: version 3. I think I want to have a jagged array. And after learning from the fellow guys. Here is my code fix, and it compile fine in VSTS 2008. What I want is a jagged array, and currently I need to have only one element. Could anyone review whether my code is correct to implement my goal please? namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1][][]; foos[0] = new Foo[1][]; foos[0][0] = new Foo[1]; foos[0][0][0] = new Foo(); return; } } } thanks in advance, George

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• C++ union data-structure, easy acccess of bits within a DWORD

  - by TK

  Im running through a set of DirectX tutorials online and I have the following structure: struct CUSTOMVERTEX { FLOAT x, y, z, rhw; // from the D3DFVF_XYZRHW flag DWORD color; // from the D3DFVF_DIFFUSE flag } My basic understanding of directX leads me to thing tha color is made up of 8-bit alpha, red, green and blue channels. I am attempting to get east access to these channels. Rather than write the following code numerous times (within the CUSTOMVERTEX structure): public: int red() { return (color & 0x00FF0000) >> 16; } I could write a more elegant somution with a combination of a union and a structure e.g. struct CUSTOMVERTEX { FLOAT x, y, z, rhw; // from the D3DFVF_XYZRHW flag #pragma pack(2) union { DWORD color; // from the D3DFVF_DIFFUSE flag struct { char a; char r; char g; char b; }; }; } However this does not appear to function as expected, the values in r, g, & b almost appear the reverse of whats in color e.g. if color is 0x12345678 a = 0x78, r = 0x56. Is this an endieness issue? Also what other problems could I be expecting from this solution? e.g. overflow from the color members? I guess what Im asking is ... is there a better way to do this?!

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• Why are changes to classes ignored after dom changes?

  - by Lg102

  I have a price grid that uses relative positioning to move a field around, beneath a box with: overflow: hidden;. In this is field, there are absolute-positioned boxes containing prices. When this box is hovered, the matching values above and left of the will change color. In order to achieve this, a class is toggled using jQuery. This initially works. However, after the grid is moved, the class change doesn't affect the block above the grid anymore. In the Chrome console, i can see the class being added, but it's css-styling isn't applied. No other styles for the element have changed. I am 100% sure there is no other style-rule influencing the element, it just stops responding to the change in class after the DOM has been altered. Can i 'refresh' the DOM somehow? Edit: I've tried to get the relevant code only: Adding the cell in the first place: $("#price_dates_cells").append("<div id='"+weekday[theBeginDate.getDay()]+"-"+theBeginDate.getDate()+"-"+(theBeginDate.getMonth()-1)+"' class='datecell' style='left: "+( Math.floor( difference / ( 3600 * 24 * 1000) ) * ( cellwidth ) )+"px'>"+weekday[theBeginDate.getDay()]+"<br>"+theBeginDate.getDate()+" "+yearmonth[theBeginDate.getMonth()]+"</div>"); Toggle the class: var str_element = "#"+weekday[Bdate.getDay()]+"-"+Bdate.getDate()+"-"+(Bdate.getMonth()-1); $(str_element).toggleClass("red"); and the movement that seems to cause the problem: $('#price_grid').animate({"top": (( ( horizontalMovement ) * cellheight)) }, 'fast', 'linear');

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• one-to-many with criteria question

  - by brnzn

  enter code hereI want to apply restrictions on the list of items, so only items from a given dates will be retrieved. Here are my mappings: <class name="MyClass" table="MyTable" mutable="false" > <cache usage="read-only"/> <id name="myId" column="myId" type="integer"/> <property name="myProp" type="string" column="prop"/> <list name="items" inverse="true" cascade="none"> <key column="myId"/> <list-index column="itemVersion"/> <one-to-many class="Item"/> </list> </class> <class name="Item" table="Items" mutable="false" > <cache usage="read-only"/> <id name="myId" column="myId" type="integer"/> <property name="itemVersion" type="string" column="version"/> <property name="startDate" type="date" column="startDate"/> </class> I tried this code: Criteria crit = session.createCriteria(MyClass.class); crit.add( Restrictions.eq("myId", new Integer(1))); crit = crit.createCriteria("items").add( Restrictions.le("startDate", new Date()) ); which result the following quires: select ... from MyTable this_ inner join Items items1_ on this_.myId=items1_.myId where this_.myId=? and items1_.startDate<=? followed by select ... from Items items0_ where items0_.myId=? But what I need is something like: select ... from MyTable this_ where this_.myId=? followed by select ... from Items items0_ where items0_.myId=? and items0_.startDate<=? Any idea how I can apply a criteria on the list of items?

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• Analyzing an IronPython Scope

  - by Vercinegetorix

  I'm trying to write C# code with an embedded IronPython script. Then want to analyze the contents of the script, i.e. list all variables, functions, class and their members/methods. There's an easy way to start, assuming I've got a scope defined and code executed in it already: dynamic variables=pyScope.GetVariables(); foreach (string v in variables) { dynamic dynamicV=pyScope.GetVariable(); /*seems to return everything. variables, functions, classes, instances of classes*/ } But how do I figure out what the type of a variable is? For the following python 'objects', dynamicV.GetType() will return different values: x=5 --system.Int32 y="asdf" --system.String def func():... --IronPython.Runtime.PythonFunction z=class() -- IronPython.Runtime.Types.OldInstance, how can I identify what the actual python class is? class NewClass -- throws an error, GetType() is unavailable. This is almost what I'm looking for. I could capture the exception thrown when unavailable and assume it's a class declaration, but that seems unclean. Is there a better approach? To discover the members/methods of a class it looks like I can use: ObjectOperations op = pyEngine.Operations; object instance = op.Call("className"); foreach (string j in op.GetMemberNames("className")) { object member=op.GetMember(instance, j); Console.WriteLine(member.GetType()); /*once again, GetType() provides some info about the type of the member, but returns null sometimes*/ } Also, how do I get the parameters to a method? Thanks!

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• Magic Method __set() on a Instantiated Object

  - by streetparade

  Ok i have a problem, sorry if i cant explaint it clear but the code speaks for its self. i have a class which generates objects from a given class name; Say we say the class is Modules: public function name($name) { $this->includeModule($name); try { $module = new ReflectionClass($name); $instance = $module->isInstantiable() ? $module->newInstance() : "Err"; $this->addDelegate($instance); } catch(Exception $e) { Modules::Name("Logger")->log($e->getMessage()); } return $this; } The AddDelegate Method: protected function addDelegate($delegate) { $this->aDelegates[] = $delegate; } The __call Method public function __call($methodName, $parameters) { $delegated = false; foreach ($this->aDelegates as $delegate) { if(class_exists(get_class($delegate))) { if(method_exists($delegate,$methodName)) { $method = new ReflectionMethod(get_class($delegate), $methodName); $function = array($delegate, $methodName); return call_user_func_array($function, $parameters); } } } The __get Method public function __get($property) { foreach($this->aDelegates as $delegate) { if ($delegate->$property !== false) { return $delegate->$property; } } } All this works fine expect the function __set public function __set($property,$value) { //print_r($this->aDelegates); foreach($this->aDelegates as $k=>$delegate) { //print_r($k); //print_r($delegate); if (property_exists($delegate, $property)) { $delegate->$property = $value; } } //$this->addDelegate($delegate); print_r($this->aDelegates); } class tester { public function __set($name,$value) { self::$module->name(self::$name)->__set($name,$value); } } Module::test("logger")->log("test"); // this logs, it works echo Module::test("logger")->path; //prints /home/bla/test/ this is also correct But i cant set any value to class log like this Module::tester("logger")->path ="/home/bla/test/log/"; The path property of class logger is public so its not a problem of protected or private property access. How can i solve this issue? I hope i could explain my problem clear.

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• C# How to create various objects at runtime that can hold strongly typed data?

  - by JL

  Is it possible to create objects at runtime without having to have hard coded class definitions, then populate properties with primitives or even strongly typed data types? For example: Lets say I want to an XML config file that could hold configuration values for connecting to various systems in an SOA application. In C# I read in these values, but for each system the properties are different (e.g: SQL might have a connection string, while SharePoint might need a username + password + domain + url, while yet an smtp server would need username + password + port + url) So instead of creating static classes as follows public class SharePointConfiguration or public class SQLConfiguration, then have each class with custom properties (this is cumbersome) Is there not a more preferred way to achieve this, without using 1990's methods, in otherwords it would still be nice to have intellisense and code completion and named properties. Since this collection of properties (object) would be passed within the class and possible to other classes from function to function I am also wondering where this class definition would get defined if its all happening at run time. Any recommendations, and hope the question was clear enough. Would like to use language features, not hacks. Thank you.

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• C Programming - Passing a pointer to array

  - by Pedro

  How do I pass a pointer value to an array of the struct; For example, on a txt I have this: John Doe;[email protected];214425532; My code: typedef struct Person{ char name[100]; char email[100]; int phone; }PERSON; int main(){ PERSON persons[100]; FILE *fp; char *ap_name; char *ap_email; char *ap_phone; char line[100]; fp=("text.txt","r"); if(fp==NULL){ exit(1); } else{ fgets(line,100,fp); ap_name=strtok(line,";"); ap_email=strtok(NULL,";"); ap_phone=strtok(NULL,";"); } return 0; } My question is how can I pass the value of ap_name, ap_email, ap_phone to the struct? And, do I need to use all of these pointers?

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• Generic Constraints And Type Parameters Mess

  - by Dummy01

  Hi everyone, I have the following base abstract class defined as: public abstract class BaseObject<T> : IComparable, IComparable<T>, IEquatable<T> {} I also have an interface defined as: public interface ICode<T> where T : struct { T Code { get; } } Now I want to derive a class that is inherited from BaseObject<T> and includes interface ICode<T>. I tried to define it like that: public class DerivedObject<T, U> : BaseObject<T>, ICode<U> where T : DerivedObject<T, U> where U : struct { public DerivedObject(U code) { Code = code; } // From BaseObject protected override int InstanceCompareTo(T obj) { return Code.CompareTo(obj.Code); } // From BaseObject protected override bool InstanceEquals(T obj) { return Code.Equals(obj.Code); } // From ICode U _Code; public U Code { get { return _Code; } protected set { _Code = value; } } } The only error that comes from the compiler is for Code.CompareTo(obj.Code) with the message: 'U' does not contain a definition for 'CompareTo' and no extension method 'CompareTo' accepting a first argument of type 'U' could be found. But U is a value type and should know CompareTo. Have you any idea what I am doing wrong, or if I do all wrong? My final aim is to derive classes such these: public class Account : DerivedObject<Account, int> public class ItemGroup : DerivedObject<ItemGroup, string> Big Thanks In Advance!

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• [Ruby on Rails] complex model relationship

  - by siulamvictor

  I am not sure am I doing these correct. I have 3 models, Account, User, and Event. Account contains a group of Users. Each User have its own username and password for login, but they can access the same Account data under the same Account. Events is create by a User, which other Users in the same Account can also read or edit it. I created the following migrations and models. User migration class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.integer :account_id t.string :username t.string :password t.timestamps end end def self.down drop_table :users end end Account migration class CreateAccounts < ActiveRecord::Migration def self.up create_table :accounts do |t| t.string :name t.timestamps end end def self.down drop_table :accounts end end Event migration class CreateEvents < ActiveRecord::Migration def self.up create_table :events do |t| t.integer :account_id t.integer :user_id t.string :name t.string :location t.timestamps end end def self.down drop_table :events end end Account model class Account < ActiveRecord::Base has_many :users has_many :events end User model class User < ActiveRecord::Base belongs_to :account end Event model class Event < ActiveRecord::Base belongs_to :account belongs_to :user end so.... Is this setting correct? Every time when a user create a new account, the system will as for the user information, i.e. username and password. How can I add them into correct tables? How can I add a new event? I am sorry for such a long question. I am not very understand the rails way in handling such data structure. Thank you guys for answering me. :)

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• Is it possible to tie nested generics?

  - by Michael Deardeuff

  Is it possible to tie nested generics/captures together? I often have the problem of having a Map lookup of class to genericized item of said class. In concrete terms I want something like this (no, T is not declared anywhere). private Map<Class<T>, ServiceLoader<T>> loaders = Maps.newHashMap(); In short, I want loaders.put/get to have semantics something like these: <T> ServiceLoader<T> get(Class<T> klass) {...} <T> void put(Class<T> klass, ServiceLoader<T> loader) {...} Is the following the best I can do? Do I have to live with the inevitable @SuppressWarnings("unchecked") somewhere down the line? private Map<Class<?>, ServiceLoader<?>> loaders = Maps.newHashMap();

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• Cannot Find Symbol Method?

  - by Aaron

  In my driver program, This line gives me cannot find symbol error and I don't know why, the method is clearly defined in the SavingsAccount class, and I can refer to all other methods in my driver program but just not that one, I tried changing the type to double, and etc but still not working. Refer to ** Account acct2 = new SavingsAccount (name); acct2.calculateBalance(); SavingsAccount Class Inherited from Account Class: public class SavingsAccount extends Account { private final short minBalance = 0; private double overdraftFee; private double yearlyInterestRate = 0.02; private double interestAmount; public SavingsAccount (String name) { super(name); } public double withdraw (double amount) { if (accountBalance - amount >= minBalance) { accountBalance -= amount; System.out.print ("Withdraw Successful"); } else { accountBalance -= amount; overdraftFee = accountBalance * (0.10); accountBalance += overdraftFee; System.out.print ("Withdraw Succesful, however overdraft fee of 10% has been applied to your account"); } return accountBalance; } **public void calculateBalance () { interestAmount = (accountBalance * yearlyInterestRate); accountBalance += interestAmount; }** public String toString() { return super.toString() + " Interest Received: " + interestAmount; } } Account class, if needed import java.util.Random; import java.text.NumberFormat; public abstract class Account { protected double accountBalance; protected long accountNumber; protected String accountHolder; public Account (String name) { accountHolder = name; accountBalance = 0; Random accountNo = new Random(); accountNumber = accountNo.nextInt(100000); } public double deposit (double amount) { accountBalance += amount; return accountBalance; } public String toString() { NumberFormat accountBal = NumberFormat.getCurrencyInstance(); return "Account Balance: " + accountBal.format(accountBalance) + "\nAccount Number: " + accountNumber; } public String getAccountHolder() { return accountHolder; } public double getAccountBalance() { return accountBalance; } public abstract double withdraw (double amount); }

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• Will this cause a problem with different runtimes with DLL?

  - by Milo

  My gui application supports polymorphic timed events so that means that the user calls new, and the gui calls delete. This can create a problem if the runtimes are incompatible. So I was told a proposed solution would be this: class base; class Deallocator { void operator()(base* ptr) { delete ptr; } } class base { public: base(Deallocator dealloc) { m_deleteFunc = dealloc; } ~base() { m_deleteFunc(this); } private: Deallocator m_deleteFunc; } int main { Deallocator deletefunc; base baseObj(deletefunc); } While this is a good solution, it does demand that the user create a Deallocator object which I do not want. I was however wondering if I provided a Deallocator to each derived class: eg class derived : public base { Deallocator dealloc; public: Derived() : base(dealloc); { } }; I think this still does not work though. The constraint is that: The addTimedEvent() function is part of the Widget class which is also in the dll, but it is instanced by the user. The other constraint is that some classes which derive from Widget call this function with their own timed event classes. Given that "he who called new must call delete" what could work given these constraints? Thanks

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• Java constructor using generic types

  - by Beer Me

  I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method breweryMethod() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // breweryMethod() is an instance method // of Brewery, of which <T> is a subclass (right?) c.breweryMethod(); // "The method breweryMethod() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void brewerySubClassMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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