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  • Minimal framework in Scala for collections with inheriting return type

    - by Rex Kerr
    Suppose one wants to build a novel generic class, Novel[A]. This class will contain lots of useful methods--perhaps it is a type of collection--and therefore you want to subclass it. But you want the methods to return the type of the subclass, not the original type. In Scala 2.8, what is the minimal amount of work one has to do so that methods of that class will return the relevant subclass, not the original? For example, class Novel[A] /* What goes here? */ { /* Must you have stuff here? */ def reverse/* What goes here instead of :Novel[A]? */ = //... def revrev/*?*/ = reverse.reverse } class ShortStory[A] extends Novel[A] /* What goes here? */ { override def reverse: /*?*/ = //... } val ss = new ShortStory[String] val ss2 = ss.revrev // Type had better be ShortStory[String], not Novel[String] Does this minimal amount change if you want Novel to be covariant? (The 2.8 collections do this among other things, but they also play with return types in more fancy (and useful) ways--the question is how little framework one can get away with if one only wants this subtypes-always-return-subtypes feature.)

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  • Django - Problem with models/manager to organise a query...

    - by user296644
    Hi, I have an application to count the number of access to an object for each website in a same database. class SimpleHit(models.Model): """ Hit is the hit counter of a given object """ content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') site = models.ForeignKey(Site) hits_total = models.PositiveIntegerField(default=0, blank=True) [...] class SimpleHitManager(models.Manager): def get_query_set(self): print self.model._meta.fields qset = super(SimpleHitManager, self).get_query_set() qset = qset.filter(hits__site=settings.SITE_ID) return qset class SimpleHitBase(models.Model): hits = generic.GenericRelation(SimpleHit) objects = SimpleHitManager() _hits = None def _db_get_hits(self, only=None): if self._hits == None: try: self._hits = self.hits.get(site=settings.SITE_ID) except SimpleHit.DoesNotExist: self._hits = SimpleHit() return self._hits @property def hits_total(self): return self._db_get_hits().hits_total [...] class Meta: abstract = True And I have a model like: class Model(SimpleHitBase): name = models.CharField(max_length=255) url = models.CharField(max_length=255) rss = models.CharField(max_length=255) creation = AutoNowAddDateTimeField() update = AutoNowDateTimeField() So, my problem is this one: when I call Model.objects.all(), I would like to have one request for the SQL (not two). In this case: one for Model in order to have information and one for the hits in order to have the counter (hits_total). This is because I cannot call directly hits.hits_total (due to SITE_ID?). I have tried select_related, but it seems to do not work... Question: - How can I add column automatically like (SELECT hits.hits_total, model.* FROM [...]) to the queryset? - Or use a functional select_related with my models? I want this model could be plugable on all other existing model. Thank you, Best regards.

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  • The pImpl idiom and Testability

    - by Rimo
    The pImpl idiom in c++ aims to hide the implementation details (=private members) of a class from the users of that class. However it also hides some of the dependencies of that class which is usually regarded bad from a testing point of view. For example if class A hides its implementation details in Class AImpl which is only accessible from A.cpp and AImpl depends on a lot of other classes, it becomes very difficult to unit test class A since the testing framework has no access to the methods of AImpl and also no way to inject dependency into AImpl. This has been a problem for me lately and I am beginning to think that the pImpl idiom and writing testable code don't mix well. Has anyone come across this problem before? and have you found a solution?

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  • Strange C++ thread function invocation

    - by Tony
    I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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  • What is a truly empty std::vector in C++?

    - by RyanG
    I've got a two vectors in class A that contain other class objects B and C. I know exactly how many elements these vectors are supposed to hold at maximum. In the initializer list of class A's constructor, I initialize these vectors to their max sizes (constants). If I understand this correctly, I now have a vector of objects of class B that have been initialized using their default constructor. Right? When I wrote this code, I thought this was the only way to deal with things. However, I've since learned about std::vector.reserve() and I'd like to achieve something different. I'd like to allocate memory for these vectors to grow as large as possible because adding to them is controlled by user-input, so I don't want frequent resizings. However, I iterate through this vector many, many times per second and I only currently work on objects I've flagged as "active". To have to check a boolean member of class B/C on ever iteration is silly. I don't want these objects to even BE there for my iterators to see when I run through this list. Is reserving the max space ahead of time and using push_back to add a new object to the vector a solution to this?

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  • Disregard a particular TD element

    - by RussellDias
    Below I have the code that allows me to edit a table row inline. However it edits ALL of the TDs within that row. My problem, along with the code, are stated below. Any help is appreciated. <tbody> <tr> <th scope="row">Test</th> <td class="amount">$124</td> <td class="amount" id="" >$154</td> <td class="diff">- 754</td> </tr> </tbody> The above table is just a sample. What I have been trying to accomplish is, to simply edit the TDs within that particular row, but I need it to disregard the diff TD. I'm fairly new to jQuery and have got the following code via the help of a jQuery book. $(document).ready(function() { TABLE.formwork('#current-expenses'); }); var TABLE = {}; TABLE.formwork = function(table){ var $tables = $(table); $tables.each(function () { var _table = $(this); _table.find('thead tr').append($('<th class="edit">&nbsp;</th>')); _table.find('tbody tr').append($('<td class="edit"><input type="button" value="Edit"/></td>')) }); $tables.find('.edit :button').live('click', function(e) { TABLE.editable(this); e.preventDefault(); }); } TABLE.editable = function(button) { var $button = $(button); var $row = $button.parents('tbody tr'); var $cells = $row.children('td').not('.edit'); if($row.data('flag')) { // in edit mode, move back to table // cell methods $cells.each(function () { var _cell = $(this); _cell.html(_cell.find('input').val()); }) $row.data('flag',false); $button.val('Edit'); } else { // in table mode, move to edit mode // cell methods $cells.each(function() { var _cell = $(this); _cell.data('text', _cell.html()).html(''); if($('td.diff')){ var $input = $('<input type="text" />') .val(_cell.data('text')) .width(_cell.width() - 16); _cell.append($input); } }) $row.data('flag', true); $button.val('Save'); } } I have attempted to alter the code so that it would disregard the diff class TD, but have had no luck so far.

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  • Unable to .append(); without eliminating all the spaces in the code

    - by Adam
    $('#form_holder').append('<div id="spec_id_'+count+'"><div class="avail_container"> <input class="avail_fields" type="checkbox" checked="checked" name="special'+count+'" /><span class="avail_field_label">Special Date</span></div> <div class="avail_container"><div class="avail_time_container"><span class="field_label">Time</span> <select name="special'+count+'_time_from_1"> <?php for ($t = 0; $t<24; $t++){ ?> <option value="<?php echo $t; ?>"><?php echo $t; ?></option> <?php } ?> </select>: <select name="special'+count+'_time_from_2"> <?php for ($t = 0; $t<60; $t+=15){ ?> <option value="<?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?>"><?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?></option> <?php } ?> </select> <span class="field_label">to</span> <select name="special'+count+'_time_to_1"> <?php for ($t = 0; $t<24; $t++){ ?> <option value="<?php echo $t; ?>"><?php echo $t; ?></option> <?php } ?> </select>: <select name="special'+count+'_time_to_2"> <?php for ($t = 0; $t<60; $t+=15){ ?> <option value="<?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?>"><?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?></option> <?php } ?> </select> </div> </div> </div>'); I'm assuming javascript or jquery does not like breaks like I have here, because all my javascript code does not work. What would be an alternative to eliminating all the spaces, which would make viewing the code difficult?

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  • pagination panel should remain static

    - by fusion
    i've a search form in which a user enters the keyword and the results are displayed with pagination. everything works fine except for the fact that when the user clicks on the 'Next' button, the pagination panel disappears as well when the page loads to retrieve the data through ajax. how do i make the pagination panel static, while the data is being retrieved? search.html: <form name="myform" class="wrapper"> <input type="text" name="q" id="q" onkeyup="showPage();" class="txt_search"/> <input type="button" name="button" onclick="showPage();" class="button"/> <p> </p> <div id="txtHint"></div> </form> ajax: var url="search.php"; url += "?q="+str+"&page="+page+"&list="; url += "&sid="+Math.random(); xmlHttp.onreadystatechange=stateChanged; xmlHttp.open("GET",url,true); xmlHttp.send(null); function stateChanged(){ if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ document.getElementById("txtHint").innerHTML=xmlHttp.responseText; } //end if } //end function search.php: $self = $_SERVER['PHP_SELF']; $limit = 3; //Number of results per page $adjacents = 2; $numpages=ceil($totalrows/$limit); $query = $query." ORDER BY idQuotes LIMIT " . ($page-1)*$limit . ",$limit"; $result = mysql_query($query, $conn) or die('Error:' .mysql_error()); ?> <div class="search_caption">Search Results</div> <div class="search_div"> <table class="result"> <?php while ($row= mysql_fetch_array($result, MYSQL_ASSOC)) { $cQuote = highlightWords(htmlspecialchars($row['cQuotes']), $search_result); ?> <tr> . . .display results. . . </tr> <?php } ?> </table> </div> <hr> <div class="searchmain"> <?php //Create and print the Navigation bar $nav=""; $next = $page+1; $prev = $page-1; if($page > 1) { $nav .= "<a onclick=\"showPage('','$prev'); return false;\" href=\"$self?page=" . $prev . "&q=" .urlencode($search_result) . "\">< Prev</a>"; $first = "<a onclick=\"showPage('','1'); return false;\" href=\"$self?page=1&q=" .urlencode($search_result) . "\"> << </a>" ; } else { $nav .= "&nbsp;"; $first = "&nbsp;"; } for($i = 1 ; $i <= $numpages ; $i++) { if($i == $page) { $nav .= "<span class=\"no_link\">$i</span>"; }else{ $nav .= "<a onclick=\"showPage('',$i); return false;\" href=\"$self?page=" . $i . "&q=" .urlencode($search_result) . "\">$i</a>"; } } if($page < $numpages) { $nav .= "<a onclick=\"showPage('','$next'); return false;\" href=\"$self?page=" . $next . "&q=" .urlencode($search_result) . "\">Next ></a>"; $last = "<a onclick=\"showPage('','$numpages'); return false;\" href=\"$self?page=$numpages&q=" .urlencode($search_result) . "\"> >> </a>"; } else { $nav .= "&nbsp;"; $last = "&nbsp;"; } echo $first . $nav . $last; ?> </div>

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  • Dynamic class_name for has_many relations

    - by vooD
    I'm trying to make has_many relation with dynamic class_name attribute class Category < ActiveRecord::Base has_many :ads, :class_name => ( lambda { return self.item_type } ) end or class Category < ActiveRecord::Base has_many :ads, :class_name => self.item_type end But i got errors: can't convert Proc into String or undefined method `item_type' for #<Class:0xb62c6c88> Thank you for any help!

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  • how to list out the submited data in same page where form submitted?

    - by OM The Eternity
    I have a form with 3 text values and one image.. I want to save these values such that i can display these records in the list below.. how can i do that... I am using osCommerce For example: <form method="post" id="fm-form" action ="" enctype="multipart/form-data"> <label>Name:</label> <input type="text" id="fm-name" name="fm-name" value="" /> <label>Email:</label> <input type="text" id="fm-email" name="fm-email" value="" /> <label>Birthdate:</label> <input type="text" id="fm-birthdate" name="fm-birthdate" value="" /> <input type="file" id="fm-image" name="fm-image"/> <input type="submit" id="fm-submit" value="Save it"> </form> <table width="100%" border="0" cellspacing="0" cellpadding="0"> <tr > <td align="center" class="productListing-heading">Product(s)</td> <td align="center" class="productListing-heading">Edit</td> <td align="center" class="productListing-heading">Delete</td> </tr> <?php for($i=0;$i<$count_image;$i++){?> <tr> <td align="left" class="productListing-data1"> <?php echo tep_image(DIR_WS_IMAGES . $file_realname, $save_image[$i], '110', '110');?> </td> <td align="center" class="productListing-data1">Edit</td> <td align="center" class="productListing-data1">Delete</td> </tr> <tr><td>&nbsp;</td></tr> <?php }?> </table> In the above format as the form is submitted the image has to be stored in a count_image array variable... and the on its count, the list below the form is displayed.. but i cannot get it worked.. could u pls help in doing this...

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  • Asp.net static object behaviour

    - by Circadian
    I have the following class as part of an asp.net application. public sealed class SomeClass { private static string appId = Guid.NewGuid().ToString(); public static ReadSomethingFromDb(){} public static WriteSomethingToDb(){} } There are more than one application instances in the same application pool, and they all access the same database. I want the operations performed by the above class to be uniquely tied to the instance that performed it, hence the use of the appId. So adding a record to the database would for example contain a name, address and appId. This has been simplified for discussion purposes. Assuming that I have two instances running at mysite.a and mysite.b the above class would generate two different guids. My problem is that mysite.a sometimes produces more than one guid, which is unexpected. Thank you in advance

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  • Create a custom button

    - by Beppi Menozzi
    Sorry if this is too basic. I created a new class that extends Button: public class MyButton extends Button { private Context ctx; public MyButton(Context context) { super(context); ctx = context; } private void click() { // DO WHAT I NEED (FOR EXAMPLE CHANGE BACKGROUND) } } How can make it possible that, when I setOnClickListener() from another class where I instantiated this object, the click() method is called automatically? Thanks.

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  • Constructor initialising an array of subobjects?

    - by ojw
    Say I have several objects within a class, each of which needs constructing with a different value. I can write something like this: class b { public: b(int num) { // 1 for a.b1, and 2 for a.b2 } }; class a { public: b b1; b b2; a() : b1(1), b2(2) { } }; However, is it possible to do the same thing if those multiple objects are stored in an array? My first attempt at it doesn't compile: class a { public: b bb[2]; a() : bb[0](1), bb[1](2) { } };

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  • Misunderstanding function pointer - passing it as an argument

    - by Stef
    I want to pass a member function of class A to class B via a function pointer as argument. Please advise whether this road is leading somewhere and help me fill the pothole. #include <iostream> using namespace std; class A{ public: int dosomeA(int x){ cout<< "doing some A to "<<x <<endl; return(0); } }; class B{ public: B(int (*ptr)(int)){ptr(0);}; }; int main() { A a; int (*APtr)(int)=&A::dosomeA; B b(APtr); return 0; } This brilliant piece of code leaves me with the compiler error: cannot convert int (A::*)(int)' toint (*)(int)' in initialization Firstly I want it to compile. Secondly I don't want dosomeA to be STATIC.

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  • jQueryUI widget text plus icon

    - by cf_PhillipSenn
    I have: <div class="ui-widget"> <div class="ui-widget-header"> My Menu<span class="ui-icon ui-icon-circle-triangle-n"></span> </div> <ul class="ui-widget-content"> <li>Menu Item 1</li> <li>Menu Item 2</li> <li>Menu Item 3</li> </ul> </div> Right now, the ui-icon is appearing below "My Menu" Q: How can I get "My Menu" to appear on the same line as the UI widget?

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  • What to prefer in the following case?

    - by GK
    say suppose I have class as : public class Age { private int age; public int getAge() { return this.age; } } In my Main class I am calling the getAge() method many times. So I wanted to know is it advisable to call so many times or call once and assign it to some variable and use that variable. Which is best and why?

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  • what is the reason i am getting out put is 111?

    - by kam
    Hi, #include "stdafx.h" #include<iostream.h> template<class T> class Sample { public: Sample(); static int i; }; template<class T> int Sample<T>::i = 0; template<class T> Sample<T>::Sample() { i++; cout<<i; } void main() { Sample<int>s1; Sample<float>s2; Sample<char>s3; } output: 111 what is the reason i am getting out put is 111?

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  • Make qwidget in new window in PyQt4

    - by matt
    I'm trying to make a class that extends qwidget, that pops up a new window, I must be missing something fundamental, class NewQuery(QtGui.QWidget): def __init__(self, parent): QtGui.QMainWindow.__init__(self,parent) self.setWindowTitle('Add New Query') grid = QtGui.QGridLayout() label = QtGui.QLabel('blah') grid.addWidget(label,0,0) self.setLayout(grid) self.resize(300,200) when a new instance of this is made in main window's class, and show() called, the content is overlaid on the main window, how can I make it display in a new window?

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  • Calling a constructor to reinitialize variables doesn't seem to work?

    - by Matt
    I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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  • How can I avoid huge communication classes in WCF?

    - by mafutrct
    My understanding is that all contract-implementing code has to be in a single class, that can become very large, obviously. How do I avoid this? I really prefer to have a few small classes doing one part of the communication with clients than a single behemoth class. The only idea I could think of is using multiple interfaces implemented by a single class split up by partial, but I don't this this is really solving the issue.

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  • doubt in - Function Objects - c++

    - by Eternal Learner
    I have a class class fobj{ public: fobj(int i):id(i) {} void operator()() { std::cout<<"Prints"<<std::endl; } private: int id; }; template<typename T> void func(T type) { type(); } My Doubt is if I invoke func like Method 1: func(fobj(1); the message I wanted to print is printed. I was always thinking I needed to do something like Method 2: fobj Iobj(1); // create an instance of the fobj class func(Iobj); //call func by passing Iobj(which is a function object) How does Method 1 work? I mean what exactly happens? and how is a call made to the operator() in class fobj ?

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  • [Ruby On Rails] belongs_to with :class_name option fails.

    - by crackpot
    I have no idea what went wrong but I can't get belongs_to work with :class_name option. Could somebody enlighten me. Thanks a lot! Here is a snip from my code. class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.text :name end end def self.down drop_table :users end end ##################################################### class CreateBooks < ActiveRecord::Migration def self.up create_table :books do |t| t.text :title t.integer :author_id, :null => false end end def self.down drop_table :books end end ##################################################### class User < ActiveRecord::Base has_many: books end ##################################################### class Book < ActiveRecord::Base belongs_to :author, :class_name => 'User', :validate => true end ##################################################### class BooksController < ApplicationController def create user = User.new({:name => 'John Woo'}) user.save @failed_book = Book.new({:title => 'Failed!', :author => @user}) @failed_book.save # missing author_id @success_book = Book.new({:title => 'Nice day', :author_id => @user.id}) @success_book.save # no error! end end environment: ruby 1.9.1-p387 Rails 2.3.5

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  • Pin Control in HCS12

    - by Brian Lindsey
    A HCS12 microcontroller I had to buy for a class I had recently taken has 40 pins on the back side of it. The class was merely about computer organization, and so unfortunately, we never had a chance to cover all the capabilities of the chip itself. Now that the class is over, I have been thinking about using the to familiarize myself with the assembly language. I haven't found any sources that cover pin control and was wondering if anyone could possibly provide me with a hands-on pin tutorial.

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  • Boost singleton trouble

    - by Ockonal
    Hi guys, I have some class which uses boost singleton. It calls some function from own c++ library. This library is written in make file as dependence. Now I have another singleton class and it should call first singleton class. After this code I got linkers error about undefined references for functions which are used in first singleton. When I remove calling first singleton class from second the errors remove. Maybe there is something wrong?

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