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• Scala's lazy arguments: How do they work?

  - by python dude

  In the file Parsers.scala (Scala 2.9.1) from the parser combinators library I seem to have come across a lesser known Scala feature called "lazy arguments". Here's an example: def ~ [U](q: => Parser[U]): Parser[~[T, U]] = { lazy val p = q // lazy argument (for(a <- this; b <- p) yield new ~(a,b)).named("~") } Apparently, there's something going on here with the assignment of the call-by-name argument q to the lazy val p. So far I have not been able to work out what this does and why it's useful. Can anyone help?

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• Filtering subsets using Linq

  - by Nathan Matthews

  Hi All, Imagine a have a very long enunumeration, too big to reasonably convert to a list. Imagine also that I want to remove duplicates from the list. Lastly imagine that I know that only a small subset of the initial enumeration could possibly contain duplicates. The last point makes the problem practical. Basically I want to filter out the list based on some predicate and only call Distinct() on that subset, but also recombine with the enumeration where the predicate returned false. Can anyone think of a good idiomatic Linq way of doing this? I suppose the question boils down to the following: With Linq how can you perform selective processing on a predicated enumeration and recombine the result stream with the rejected cases from the predicate?

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• JQuery Validation using Remote posts empty data to webservice

  - by user319721

  I'm using the JQuery Validation plugin. I'm using the remote option to make a call to my webservice to check if a company name exists. The webservice only accepts JSON data. I pass the data to the webservice from the Company Input Field in my Form as follows: data: "{'company': '" + $('#Company').val() + "'}" But this always returns a blank value for company so the response is {'company':''} i.e. correct JSON but missing the Company Input Field value. Can anyone shed some light on why I always get a blank value here? Thanks for the help, Ciaran

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• How do I dynamically update an instance array to hold a list of dynamic methods on instantiation?

  - by Will

  I am trying to dynamically define methods based on xml mappings. This works really well. However I want to create an instance variable that is a array of the dynamically defined methods. My code looks something like this def xml_attr_reader(*args) xml_list = "" args.each do |arg| string_val = "def #{arg}; " + " xml_mapping.#{arg}; " + "end; " self.class_eval string_val xml_hash = xml_list + "'#{arg}'," end self.class_eval "@xml_attributes = [] if @xml_attributes.nil?;" + "@xml_attributes = @xml_attributes + [#{xml_list}];" + "puts 'xml_attrs = ' + @xml_attributes.to_s;" + "def xml_attributes;" + " puts 'xml_attrs = ' + @xml_attributes.to_s;" + " @xml_attributes;" + "end" end So everything works except when I call xml_attributes on an instance it return null (and prints out 'xml_attrs = '). While the puts before the definition actually prints out the correct array. (when I instantiate the instance)

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• Elegant way for a recursive C++ template to do something different with the leaf class?

  - by Costas

  I have a C++ class template that makes an Array of pointers. This also gets typedefed to make Arrays of Arrays and so on: typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; I would like to be able to set one leaf node from another by copying the pointer so they both refer to the same Elem. But I also want to be able to set one Array (or Array of Arrays etc) from another. In this case I don't want to copy the pointers, I want to keep the arrays seperate and descend into each one until I get to the leaf node, at where I finally copy the pointers. I have code that does this (below). When you set something in an Array it calls a CopyIn method to do the copying. But because this is templated it also has to call the CopyIn method on the leaf class, which means I have to add a dummy method to every leaf class that just returns false. I have also tried adding a flag to the template to tell it whether it contains Arrays or not, and so whether to call the CopyIn method. This works fine - the CopyIn method of the leaf nodes never gets called, but it still has to be there for the compile to work! Is there a better way to do this? #include <stdio.h> class Elem { public: Elem(int v) : mI(v) {} void Print() { printf("%d\n",mI); } bool CopyIn(Elem *v) { return false; } int mI; }; template < typename T > class Array { public: Array(int size) : mB(0), mN(size) { mB = new T* [size]; for (int i=0; i<mN; i++) mB[i] = new T(mN); } ~Array() { for (int i=0; i<mN; i++) delete mB[i]; delete [] mB; } T* Get(int i) { return mB[i]; } void Set(int i, T* v) { if (! mB[i]->CopyIn(v) ) { // its not an array, so copy the pointer mB[i] = v; } } bool CopyIn(Array<T>* v) { for (int i=0; i<mN; i++) { if (v && i < v->mN ) { if ( ! mB[i]->CopyIn( v->mB[i] )) { // its not an array, so copy the pointer mB[i] = v->mB[i]; } } else { mB[i] = 0; } } return true; // we did the copy, no need to copy pointer } void Print() { for (int i=0; i<mN; i++) { printf("[%d] ",i); mB[i]->Print(); } } private: T **mB; int mN; }; typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; int main () { ElemArrayArrayArray* a = new ElemArrayArrayArray(2); ElemArrayArrayArray* b = new ElemArrayArrayArray(3); // In this case I need to copy the pointer to the Elem into the ElemArrayArray a->Get(0)->Get(0)->Set(0, b->Get(0)->Get(0)->Get(0)); // in this case I need go down through a and b until I get the to Elems // so I can copy the pointers a->Set(1,b->Get(2)); b->Get(0)->Get(0)->Get(0)->mI = 42; // this will also set a[0,0,0] b->Get(2)->Get(1)->Get(1)->mI = 96; // this will also set a[1,1,1] // should be 42,2, 2,2, 3,3, 3,96 a->Print(); }

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• C++ conditional compilation

  - by Shaown

  I have the following code snippet #ifdef DO_LOG #define log(p) record(p) #else #define log(p) #endif void record(char *data){ ..... ..... } Now if I call log("hello world") in my code and DO_LOG isn't defined, will the line be compiled, in other words will it eat up the memory for the string "hello world"? P.S. There are a lot of record calls in the program and it is memory sensitive, so is there any other way to conditionally compile so that it only depends on the #define DO_LOG? Thanks in advance.

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• Why wouldn't I be able to establish a trust relationship for a SSL/TLS channel?

  - by Abe Miessler

  I have a piece of .NET code that is erroring out when it makes a call to HTTPWebRequest.GetRequestStream. Here is the error message: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. I've read a few things that suggest that I might need a certificate on the machine running the code, but i'm not sure if that's true or how to do it. If I need to get a certificate, how do I do it? Code: var request = (HttpWebRequest)HttpWebRequest.Create(requestUrl); //my url request.Method = StringUtilities.ConvertToString(httpMethod); // Set the http method GET, POST, etc. if (postData != null) { request.ContentLength = postData.Length; request.ContentType = contentType; using (var dataStream = request.GetRequestStream()) { dataStream.Write(postData, 0, postData.Length); } }

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• Restore history and current page on resuming webview

  - by qubit

  I have a webview that I use to navigate from page to page. I have implemented go back and go forward. My problem is that when I return to the webview after visiting another activity, the history is lost i.e. the webview starts again on the first page. How do I code it so that after I call finish on the webview to swap to another activity on returning to the webview, the WebBackForwardList is restored and I am taken to the page I was on when I left the webview? I have tried overriding onSaveInstanceState and onRestoreInstanceState using webview.save/restoreState(bundle) but with no success. I have achieved returning to the last page by saving the last url in preferences, but have been unable to restore the entire history.

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• Doubt about constructor in JAVA

  - by Harry Joy

  I have few doubts regarding constructor in java Can a constructor be private? If yes then in which condition? Constructor is a method or not? If constructor does not return anything then why we are getting a new Object every time we call it. Whats the default access modifier of a constructor if we did not specify. Thanks & Regards Edit---------- Answer for 1 & 3 are very clear. But still doubt about 2&4 as i'm getting different answers for them.

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• what is the use of creating proxy for an webservice

  - by prince23

  hi, i have an webserivce written where i do an insertion opertion to DB. path :http://localhost:1838/Ajax/WebService.asmx?wsdl.name of the webservice is localhost i have added webservice for the project now on button click event i try to call this webserice like this localhost obj= new localhost(); obj.insert(); now i am able to do the insertion operation fine. but i wanted to create an proxy for the webservice so wat is the use of it doing like tat? when i run this command in my command prompt in vs wsdl /out:myProxyClass.cs http://localhost:1838/Ajax/WebService.asmx?WSDL i get an error unable to connect the remote server. no connection would be made because the target machine actively refused it looking forward for an solution any help would great thank you

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• Print out the variable name objective-C

  - by vodkhang

  Continued from the last question here: Log method name in Obj-C . I just wondered if there is a way to print out the variable name as well. For example: NSString *name = "vodkhang"; NCLog(@"%@", name); and I hope that the output should be: name: vodkhang Just to summarize the previous post, currently, I can print out the class name, method name and the line number when I call NCLog(@"Hello World"); <ApplicationDelegate:applicationDidFinishLaunching:10>Hello world with #define NCLog(s, ...) NSLog(@"<%@:%d> %@", __FUNCTION__, __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__])

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• Are pointers primitive types in C++?

  - by Space_C0wb0y

  I was wondering about the last constructor for std::string mentioned here. It says: template<class InputIterator> string (InputIterator begin, InputIterator end); If InputIterator is an integral type, behaves as the sixth constructor version (the one right above this) by typecasting begin and end to call it: string(static_cast<size_t>(begin),static_cast<char>(end)); In any other case, the parameters are taken as iterators, and the content is initialized with the values of the elements that go from the element referred by iterator begin to the element right before the one referred by iterator end. So what does that mean if InputIterator is a char * ?

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• Calling this[int index] via reflection

  - by tkutter

  I try to implement a reflection-based late-bound library to Microsoft Office. The properties and methods of the Offce COM objects are called the following way: Type type = Type.GetTypeFromProgID("Word.Application"); object comObject = Activator.CreateInstance(type); type.InvokeMember(<METHOD NAME>, <BINDING FLAGS>, null, comObject, new object[] { <PARAMS>}); InvokeMember is the only possible way because Type.GetMethod / GetProperty works improperly with the COM objects. Methods and properties can be called using InvokeMember but now I have to solve the following problem: Method in the office-interop wrapper: Excel.Workbooks wb = excel.Workbooks; Excel.Workbook firstWb = wb[0]; respectively foreach(Excel.Workbook w in excel.Workbooks) // doSmth. How can I call the this[int index] operator of Excel.Workbooks via reflection?

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• How to add EAR files in a java console application

  - by Vibhas

  Hi Friends, I want to know how to add an EAR file into a simple java class i.e a standalone application. Let say i have a class Employee package com.Employee; import com.xyz.Workflow//this library is present in EAR file whose method i need to call public class Employee{ public static void main(String[] args) // Wokflow wf = new Workflow(); // ws.initiateWorkflow(); this method needs to be called but for that i need to include this EAR which is given to me from a 3rd party; } Can any one help me the API is in EAR only. Thanks

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• Can I change class types in a setter with an object-oriented language?

  - by user214626

  Hello, Here is the problem statement : Calling a setter on the object should result in the object to change to an object of a different class, which language can support this ? Ex. I have a class called "Man" (Parent Class), and two children namely "Toddler" and "Old Man", they are its children because they override a behaviour in Man called as walk.( i.e Toddler sometimes walks using both his hands and legs kneeled down and the Old man uses a stick to support himself). The Man class has a attribute called age, I have a setter on Man,say it is called setAge(int ageValue). I have 3 objects, 2 toddlers, 1 old-Man. (The system is up and running,i guess when we say objects it is obvious) .I will make this call, toddler.setAge(80), I expect the toddler to change to an object of type Old Man. Is this possible.Please suggest. Thanks,

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• How to insert value to Magento database using module

  - by Kasmin Nicko

  I want to insert value to the database I created. The value would be insert to post column. I have code like this in the IndexController.php class My_Module_IndexController extends Mage_Core_Controller_Front_Action { public function postAction() { $post = Mage::getModel('my/model'); $post->setPost('My Post Here'); $post->save(); } } But after I ran this script, I got the following error Fatal error: Call to a member function setPost() on a non-object in C:\xampp\htdocs\magento\app\code\community\My\Module\controllers\IndexController.php on line 7 What is something I miss?

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• How to pass around event as parameter in c#

  - by Jerry Liu

  Am writing unit test for a multi-threading application, where I need to wait until a specific event triggered so that I know the asyn operation is done. E.g. When I call repository.add(something), I wait for event AfterChange before doing any assertion. So I write a util function to do that. public static void SyncAction(EventHandler event_, Action action_) { var signal = new object(); EventHandler callback = null; callback = new EventHandler((s, e) => { lock (signal) { Monitor.Pulse(signal); } event_ -= callback; }); event_ += callback; lock (signal) { action_(); Assert.IsTrue(Monitor.Wait(signal, 10000)); } } However, the compiler prevents from passing event out of the class. Is there a way to achieve that?

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• Python 3: Recursivley find if number is even

  - by pythonhack

  I am writing a program that must find if a number is even or not. It needs to follow this template. I can get it to find if a number is even or not recursively (call function and subtract 2, base case zero), but I am having a hard time following this template, based on how the isEven function is called in the main function. Any help would be greatly appreciated. Write a recursive function called isEven that finds whether a number is even or not: def isEven() #recursivley determine whether number is even or not def main(): number=int(input(“Enter a number : “)) if (isEven(number)): print(“Number is even”) else: print(“Number is not even”) main() Thank you! Appreciate it.

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• jQuery sibling selector?

  - by Brett

  Hi, I have a table which I'm trying to do a pricing list, that auto-computes the tax component.. I'm getting the value from price_1, applying a math cal, and saving it to tax_1. I could read the number of the end of the id, but hopefully there is a cleaner way with jQuery. E.g. I would have a lot of fields like.. price_1 price_2 price_3 tax_1 tax_2 tax_3 etc... I can use the following code to call jQuery on change of a price, and get the value of that price. How do I update the tax field next to it? should I use a sibling selector or something?? $('#pricing').delegate("input", "change", function(){ $(this).val() /* the value of the price */; })

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• Active Record Associations:

  - by jmccartie

  I'm brand new to Rails, so bear with me. I have 3 models: User, Section, and Tick. Each section is created by a user. My guess with this association: class Section < ActiveRecord::Base has_one :user end Next, each user can "tick" off a section -- only once. So for each tick, I have a section_id, user_id, and timestamps. Here's where I'm stuck. Does this call for a "has_one :through" association? If so, which direction? If not, then I'm way off. Which association works here? Thanks!

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• removing the single quote from a list of

  - by tanky

  I need to append/format a url with a list of ids for an api call however, when i put the list at the end of the api https://api.twitter.com/1.1/users/lookup.json?user_id=%s'%a i just get an empty string as a response. i have tried turning the list into a string and removing the square brackets doing a = str(followers['ids'])[1:-1] but i still get the same problem. and im assuming that its being caused by the single quote at the start. i have tried removing the apostrophe from the string doing a.replace("'", "") and now i have run out of ideas thanks

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• Can you reuse a mysql result set in PHP?

  - by MarathonStudios

  I have a result set I pull from a large database: $result = mysql_query($sql); I loop through this recordset once to pull specific bits of data and get averages using while($row = mysql_fetch_array($result)). Later in the page, I want to loop through this same recordset again and output everything - but because I used the recordset earlier, my second loop returns nothing. I finally hacked around this by looping through a second identical recordset ($result2 = mysql_query($sql);), but I hate to make the same SQL call twice. Any way I can loop through the same dataset multiple times?

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• Use concat and maintain length of variable

  - by user1682055

  I'm trying to use concat on some variables. These variables have been declared as chars: declare v_order_date char(10); declare v_quantity char(11); declare v_plant char(100); I have a cursor where I am setting these as some outputs. To call the results, I am setting v_msg as set v_msg := concat( v_msg, '\n', v_order_date, v_quantity, v_plant); However, the result I am getting when I select v_msg is: 2012-01-222501008 Creeping Buttercup but I want to maintain the length of the declared variables in my select that looks like this 2012-01-22 250 1008 Creeping Buttercup Are there any suggestions? Thank you.

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• JNI: dll function works ok in C++ main, but not with dll wrapper

  - by Joseph Lim

  I have an a.dll (not modifiable as i do not have the source) with a function bool openPort(DWORD mem).I wrote a c++ main, loaded this dll using LoadLibrary, and the function works well.It returns true. Now, I need to call this function from Java via JNI. I wrote another b.dll with a function like so JNIEXPORT void JNICALL Java_MyClass_openPortFunc (JNIEnv *env, jobject obj, jint pMemPhy) { hInstLibrary = LoadLibrary("a.dll"); typedef bool (*openPort)(DWORD); openPort _openPort; _openPort = (openPort)GetProcAddress(hInstLibrary, "openPort"); DWORD memAddr = 0xda000; if(_openPort(memAddr)){ cout << "ok" << endl; }else{ cout << "failed " << endl; } } This however, causes the openPort to return false despite using the same parameters. I hope someone can advise me. Thank you. :)

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• How to initialise a STL vector/list with a class without invoking the copy constructor

  - by Warpspace

  I have a C++ program that uses a std::list containing instances of a class. If I call e.g. myList.push_back(MyClass(variable)); it goes through the process of creating a temporary variable, and then immediately copies it to the vector, and afterwards deletes the temporary variable. This is not nearly as efficient as I want, and sucks when you need a deep copy. I would love to have the constructor of my class new something and not have to implement a copy constructor just to allocate my memory for the second time and waste runtime. I'd also rather not have to immediately find the class instance from the vector/list and then manually allocate the memory (or do something horrible like allocate the memory in the copy constructor itself). Is there any way around this (I'm not using Visual Studio BTW)?

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