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  • Implementing the procducer-consumer pattern with .NET 4.0

    - by bitbonk
    With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing/enqueuing task items and another thread executes/dequeues these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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  • domain modeling naming problem

    - by cherouvim
    Hello There are some simple entities in an application (e.g containing only id and title) which rarely change and are being referenced by the more complex entities of the application. These are usually entities such as Country, City, Language etc. How are these called? I've used the following names for those in the past but I'm not sure which is the best way to call them: reference data lookup values dictionaries thanks

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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • How to bring the parent element with floated child elements to the center of the document?

    - by Starx
    I have organized a menu. Its HTML is as follows: <ul class="topmenu"> <li><a href="sample.html">Text 1</a></li> <li><a href="sample.html">Text 2</a></li> <li><a href="sample.html">Text 3</a></li> <li><a href="sample.html">Text 4</a></li> <ul> This is a horizontal menu, so I have floated the list items to left to appear them in a horizontal line. I could have used display:inline to appear them in a single line, but since IE does not support it and I don't know any other way to do so, I used float:left;. It's css is: .topmenu { list-style:none; margin:0; padding:0; } .topmenu li { float:left; } This brings the menu in a perfect horizontal line, but the entire list is floated to the left. I want to bring the .topmenu to appear in the center of the document and keep the listitem inside it floated towards the left. I found that this is achievable by defining width property of the .topmenu, but I dont want to fix its width as the list-items are dynamically generated and thus could increase and decrease. Any one know of any solution?

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  • One page of responsive site is blurry/fuzzy on iphone

    - by Gwendydd
    Here's a weird one. I'm developing a responsive site here: http://74.209.178.54:3000/index.html There are three pages built so far: the home page, the "Why" page, and the "Pricing" page. The Home and Why pages are just fine on my iPhone 4. The "Pricing" page is really blurry. And I don't just mean the images are blurry - absolutely everything is blurry: text, borders, backgrounds... Has anyone seen this before? Do you know what's happening?

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  • How do I calculate a good hash code for a list of strings?

    - by Ian Ringrose
    Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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  • Protecting sensitive entity data

    - by Andreas
    Hi, I'm looking for some advice on architecture for a client/server solution with some peculiarities. The client is a fairly thick one, leaving the server mostly to peristence, concurrency and infrastructure concerns. The server contains a number of entities which contain both sensitive and public information. Think for example that the entities are persons, assume that social security number and name are sensitive and age is publicly viewable. When starting the client, the user is presented with a number of entities, not disclosing any sensitive information. At any time the user can choose to log in and authenticate against the server, given the authentication is successful the user is granted access to the sensitive information. The client is hosting a domain model and I was thinking of implementing this as some kind of "lazy loading", making the first request instantiating the entities and later refreshing them with sensitive data. The entity getters would throw exceptions on sensitive information when they've not been disclosed, f.e.: class PersonImpl : PersonEntity { private bool undisclosed; public override string SocialSecurityNumber { get { if (undisclosed) throw new UndisclosedDataException(); return base.SocialSecurityNumber; } } } Another more friendly approach could be to have a value object indicating that the value is undisclosed. get { if (undisclosed) return undisclosedValue; return base.SocialSecurityNumber; } Some concerns: What if the user logs in and then out, the sensitive data has been loaded but must be disclosed once again. One could argue that this type of functionality belongs within the domain and not some infrastructural implementation(i.e. repository implementations). As always when dealing with a larger number of properties there's a risk that this type of functionality clutters the code Any insights or discussion is appreciated!

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  • how to tackle a custom forms database

    - by Neil Hickman
    I'm currently researching a project for the place that I work in. We are trying to create a system that will allow forms to be set up dynamically from a database. My question is what database structure would best suit something like this? I currently have a structure of: forms_form forms_formfields forms_formdata I don't think this is the most appropriate layout for this. Basically to make is make sense I need to be able to make a form within the database that can have infinite fields all customized and have the data when submitted stored in the database.

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  • many-to-many-to-many, incl alignment of data from diff sources

    - by JefeCoon
    Re-factoring dbase to support many:many:many. At the second and third levels we need to preserve end-user 'mapping' or aligning of data from different sources, e.g. Order 17 FirstpartyOrderID => aha LineItem_for_BigShinyThingy => AA-1 # maps to 77-a LineItem_for_BigShinyThingy => AA-2 # maps to 77-b, 77-c LineItem_for_LittleWidget => AA-x # maps to 77-zulu, 77-alpha, 99-foxtrot LineItem_for_LittleWidget => AA-y # maps to 77-zulu, 99-foxtrot LineItem_for_LittleWidget => AA-z # maps to 77-alpha ThirdpartyOrderID => foo LineItem_for_BigShinyThingy => 77-a LineItem_for_BigShinyThingy => 77-b LineItem_for_BigShinyThingy => 77-c LineItem_for_LittleWidget => 77-zulu LineItem_for_LittleWidget => 77-alpha ThirdpartyOrderID => bar LineItem_for_LittleWidget => 99-foxtrot Each LineItem has daily datapoints reported from its own source (Firstparty|Thirdparty). In our UI & app we provide tools to align these, then we'd like to save them into the cleanest possible schema for querying, enabling us to diff the reported daily datapoints, and perform other daily calculations (which we'll store in the dbase also, fortunately that should be cake once we've nailed this). We need to map related [firstparty|thirdparty]line_items which have their own respective datapoints. We'll be using the association to pull each line_items collection of datapoints for summary and discrepancy calculations. I'm considering two options, std has_many,through x2 --or-- possibly (scary) ubermasterjoin table OptionA: order<<-->> order_join_table[id,order_id,firstparty_order_id,thirdparty_order_id] <<-->>line_item order_join_table[firstparty_order_id]-->raw_order[id] order_join_table[thirdparty_order_id]-->raw_order[id] raw_order-->raw_line_items[raw_order_id] line_item<<-->> line_item_join[id,LI_join_id,firstparty_LI,thirdparty_LI <<-->>raw_line_items line_item_join[firstparty_LI]-->raw_line_item[id] line_item_join[thirdparty_LI]-->raw_line_item[id] raw_line_item<<-->>datapoints = we rely upon join to store all mappings of first|third orders & line_items = keys to raw_* enable lookup of these order & line_item details = concerns about circular references and/or lack of correct mapping logic, e.g order--line_item--raw_line_items vs. order--raw_order--raw_line_items OptionB: order<<-->> join_master[id,order_id,FP_order_id,TP_order_id,FP_line_item_id,TP_line_item_id] join_master[FP_order_id & TP_order_id]-->raw_order[id] join_master[FP_line_item_id & TP_line_item_id]-->raw_line_item[id] = every combo of FP_line_item + TP_line_item writes a record into the join_master table = "theoretically" queries easy/fast/flexible/sexy At long last, my questions: a) any learnings from painful firsthand experience about how best to implement/tune/optimize many-to-many-to-many relationships b) in rails? c) any painful gotchas (circular references, slow queries, spaghetti-monsters) to watch out for? d) any joy & goodness in Rails3 that makes this magically easy & joyful? e) anyone written the "how to do many-to-many-to-many schema in Rails and make it fast & sexy?" tutorial that I somehow haven't found? If not, I'll follow up with our learnings in the hope it's helpful.. Thanks in advance- --Jeff

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  • ruby on rails has_many through relationship

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

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  • Responsive grid, floated elements move underneath one another when min-width is reached

    - by Francesca
    I'm in the process of creating a responsive site (currently only working on the main content.) I've created two floated divs with percentage based widths. One contains an image which resizes with the browser resizing. The image has a min-width of 100px. Can anyone tell me why when put into a mobile sized width it doesn't drop down? How can I make the image stack underneath the text? JS Fiddle Live site

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  • Pagination in a Rich Domain Model

    - by user246790
    I use rich domain model in my app. The basic ideas were taken there. For example I have User and Comment entities. They are defined as following: <?php class Model_User extends Model_Abstract { public function getComments() { /** * @var Model_Mapper_Db_Comment */ $mapper = $this->getMapper(); $commentsBlob = $mapper->getUserComments($this->getId()); return new Model_Collection_Comments($commentsBlob); } } class Model_Mapper_Db_Comment extends Model_Mapper_Db_Abstract { const TABLE_NAME = 'comments'; protected $_mapperTableName = self::TABLE_NAME; public function getUserComments($user_id) { $commentsBlob = $this->_getTable()->fetchAllByUserId((int)$user_id); return $commentsBlob->toArray(); } } class Model_Comment extends Model_Abstract { } ?> Mapper's getUserComments function simply returns something like: return $this->getTable->fetchAllByUserId($user_id) which is array. fetchAllByUserId accepts $count and $offset params, but I don't know to pass them from my Controller to this function through model without rewriting all the model code. So the question is how can I organize pagination through model data (getComments). Is there a "beatiful" method to get comments from 5 to 10, not all, as getComments returns by default.

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  • C# Linq: Can you merge DataContexts?

    - by Andreas Grech
    Say I have one database, and this database has a set of tables that are general to all Clients and some tables that are specific to certain clients. Now what I have in mind is creating a primary DataContext that includes only the tables that are general to all the clients, and then create separate DataContexts that contain only the tables that are specific to the client. Is there a way to kind of "merge" DataContexts so that it becomes one context? So for Client A, I need one DataContext that includes both the general tables and also the tables for that specific client (retrieved from two different DataContexts) ? [Update] What I think I can do is, from the Partial Class of the DataContext instead of letting my DataContext inherit from DataContext I make it inherit from MyDataContext; that way, the tables from MyDataContext and the other DataContext will be available in one DataContext class. What do you think about this approach? Of course with something like this you can only merge two datacontexts at once though...

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  • Improving MVP in Scala

    - by Alexey Romanov
    The classical strongly typed MVP pattern looks like this in Scala: trait IView { } trait Presenter[View <: IView] { // or have it as an abstract type member val view : View } case class View1(...) extends IView { ... } case object Presenter1 extends Presenter[View1] { val view = View1(...) } Now, I wonder if there is any nice way to improve on it which I am missing...

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  • Simple and efficient distribution of C++/Boost source code (amalgamation)

    - by Arrieta
    Hello: My job mostly consists of engineering analysis, but I find myself distributing code more and more frequently among my colleagues. A big pain is that not every user is proficient in the intricacies of compiling source code, and I cannot distribute executables. I've been working with C++ using Boost, and the problem is that I cannot request every sysadmin of every network to install the libraries. Instead, I want to distribute a single source file (or as few as possible) so that the user can g++ source.c -o program. So, the question is: can you pack the Boost libraries with your code, and end up with a single file? I am talking about the Boost libraries which are "headers only" or "templates only". As an inspiration, please look at the distribution of SQlite or the Lemon Parser Generator; the author amalgamates the stuff into a single source file which is trivial to compile. Thank you.

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  • how to handle exceptions/errors in php?

    - by fayer
    when using 3rd part libraries they tend to throw exceptions to the browser and hence kill the script. eg. if im using doctrine and insert a duplicate record to the database it will throw an exception. i wonder, what is best practice for handling these exceptions. should i always do a try...catch? but doesn't that mean that i will have try...catch all over the script and for every single function/class i use? Or is it just for debugging? i don't quite get the picture. Cause if a record already exists in a database, i want to tell the user "Record already exists". And if i code a library or a function, should i always use "throw new Expcetion($message, $code)" when i want to create an error? Please shed a light on how one should create/handle exceptions/errors. Thanks

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  • C++ Namespaces & templates question

    - by Kotti
    Hi! I have some functions that can be grouped together, but don't belong to some object / entity and therefore can't be treated as methods. So, basically in this situation I would create a new namespace and put the definitions in a header file, the implementation in cpp file. Also (if needed) I would create an anonymous namespace in that cpp file and put all additional functions that don't have to be exposed / included to my namespace's interface there. See the code below (probably not the best example and could be done better with another program architecture, but I just can't think of a better sample...) Sample code (header) namespace algorithm { void HandleCollision(Object* object1, Object* object2); } Sample code (cpp) #include "header" // Anonymous namespace that wraps // routines that are used inside 'algorithm' methods // but don't have to be exposed namespace { void RefractObject(Object* object1) { // Do something with that object // (...) } } namespace algorithm { void HandleCollision(Object* object1, Object* object2) { if (...) RefractObject(object1); } } So far so good. I guess this is a good way to manage my code, but I don't know what should I do if I have some template-based functions and want to do basically the same. If I'm using templates, I have to put all my code in the header file. Ok, but how should I conceal some implementation details then? Like, I want to hide RefractObject function from my interface, but I can't simply remove it's declaration (just because I have all my code in a header file)... The only approach I came up with was something like: Sample code (header) namespace algorithm { // Is still exposed as a part of interface! namespace impl { template <typename T> void RefractObject(T* object1) { // Do something with that object // (...) } } template <typename T, typename Y> void HandleCollision(T* object1, Y* object2) { impl::RefractObject(object1); // Another stuff } } Any ideas how to make this better in terms of code designing?

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • Looking for Programming Language that allows you to change true and false.

    - by Maushu
    For my curiosity sake I'm looking for a dynamic object oriented language that allows you to change true to false and vice versa. Something like this: true = false, false = true; This should also affect any conditional statements, therefore 42 == 42 should return False. Basically, with this premise, nothing in the language would be safe from the programmer. Is there any language like this?

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