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  • Interpreter in C++: Function table storage problem

    - by sub
    In my interpreter I have built-in functions available in the language like print exit input, etc. These functions can obviously be accessed from inside the language. The interpreter then looks for the corresponding function with the right name in a vector and calls it via a pointer stored with its name. So I gather all these functions in files like io.cpp, string.cpp, arithmetic.cpp. But I have to add every function to the function list in the interpreter in order for it to be found. So in these function files I have things like: void print( arg ) { cout << arg.ToString; } I'd add this print function to the interpreter function list with: interpreter.AddFunc( "print", print ); But where should I call the interpreter.AddFunc? I can't just put it there below the print function as it has to be in a function according to the C++ syntax. Where and how should all the functions be added to the list?

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  • Fastest way to perform subset test operation on a large collection of sets with same domain

    - by niktech
    Assume we have trillions of sets stored somewhere. The domain for each of these sets is the same. It is also finite and discrete. So each set may be stored as a bit field (eg: 0000100111...) of a relatively short length (eg: 1024). That is, bit X in the bitfield indicates whether item X (of 1024 possible items) is included in the given set or not. Now, I want to devise a storage structure and an algorithm to efficiently answer the query: what sets in the data store have set Y as a subset. Set Y itself is not present in the data store and is specified at run time. Now the simplest way to solve this would be to AND the bitfield for set Y with bit fields of every set in the data store one by one, picking the ones whose AND result matches Y's bitfield. How can I speed this up? Is there a tree structure (index) or some smart algorithm that would allow me to perform this query without having to AND every stored set's bitfield? Are there databases that already support such operations on large collections of sets?

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  • Auto scale and rotate images

    - by Dave Jarvis
    Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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  • How can I position QDockWidgets as the screen shot shows using code?

    - by Nathan
    I want a Qt window to come up with the following arrangement of dock widgets on the right. Qt allows you to provide an argument to the addDockWidget method of QMainWindow to specify the position (top, bottom, left or right) but apparently not how two QDockWidgets placed on the same side will be arranged. Here is the code that adds the dock widgets. this uses PyQt4 but it should be the same for Qt with C++ self.memUseGraph = mem_use_widget(self) self.memUseDock = QDockWidget("Memory Usage") self.memUseDock.setObjectName("Memory Usage") self.memUseDock.setWidget(self.memUseGraph) self.addDockWidget(Qt.DockWidgetArea(Qt.RightDockWidgetArea),self.memUseDock) self.diskUsageGraph = disk_usage_widget(self) self.diskUsageDock = QDockWidget("Disk Usage") self.diskUsageDock.setObjectName("Disk Usage") self.diskUsageDock.setWidget(self.diskUsageGraph) self.addDockWidget(Qt.DockWidgetArea(Qt.RightDockWidgetArea),self.diskUsageDock) When this code is used to add both of them to the right side, one is above the other, not like the screen shot I made. The way I made that shot was to drag them there with the mouse after starting the program, but I need it to start that way.

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  • defining information out of class

    - by calccrypto
    is there a way to define a value within a class in the __init__ part, send it to some variable outside of the class without calling another function within the class? like class c: def __init__(self, a): self.a = a b = 4 # do something like this so that outside of class c, # b is set to 4 automatically when i use class c def function(self): ... # whatever. this doesnt matter i have multiple classes that have different values for b. i could just make a list that tells the computer to change b, but i would rather set b within each class

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  • How do you run your unit tests? Compiler flags? Static libraries?

    - by Christopher Gateley
    I'm just getting started with TDD and am curious as to what approaches others take to run their tests. For reference, I am using the google testing framework, but I believe the question is applicable to most other testing frameworks and to languages other than C/C++. My general approach so far has been to do either one of three things: Write the majority of the application in a static library, then create two executables. One executable is the application itself, while the other is the test runner with all of the tests. Both link to the static library. Embed the testing code directly into the application itself, and enable or disable the testing code using compiler flags. This is probably the best approach I've used so far, but clutters up the code a bit. Embed the testing code directly into the application itself, and, given certain command-line switches either run the application itself or run the tests embedded in the application. None of these solutions are particularly elegant... How do you do it?

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  • Open closed prinicple, problem

    - by Marcus
    Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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  • Reusability, testability, code complexity reduction and showing-off-ability programming importance

    - by Andrew Florko
    There are lots of programming and architecture patterns. Patterns allow to make code cleaner, reusable, more testable & at last (but not at least) to feel the follower a real cool developer. How do you rank these considerations for you? What does affect you most when you decide to apply pattern? I wonder how many times code reusability (especially for MVP, MVC patterns) was important? For example DAL library often shared between projects (it's reusable) but how often controllers/views (abstracted via interfaces) are reused?

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  • implementing a Intelligent File Transfer Software in java over TCP/IP

    - by whyjava
    Hello I am working on a proposal where we have to implement a software which can move files between one source to destination.The overall goal of this project is to create intelligent file transfer.This software will have three components :- 1) Broker : Broker is the module that communicates with other brokers, monitors files, moves files, retrieves configurations from the Configuration Manager, supplies process information for the monitor, archives files, writes all process data to log files and escalates issues if necessary 2) Configuration Manager :Configuration Manager is a web-based application used to configure and deploy the configuration to all brokers. 3) Monitor : Monitor is a web-based application used to monitor each Broker in the environment. This project has to be built up in java and protocol for file transfer in tcp/ip. Client does not want to use FTP. File Transfer seems very easy, until there are several processes who are waiting to pick the file up automatically. Several problems arise: How can we guarantee the file is received at the destination? If a file isn’t received the first time, we should try it again (even after a restart or power breakdown) ? How does the receiver knows the file that is received is complete? How can we transfer multiple files synchronously? How can we protect the bandwidth, so file transfer isn’t blocking other processes? How does one interoperate between multiple OS platforms? What about authentication? How can we monitor het workflow? Auditing / logging Archiving Can you please provide answer to some of these? Thanks

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  • Best Practices & Considerations when writing HTML Emails

    - by Jonathan Sampson
    I've been developing websites for over a decade now, but quickly found that many of my habits in developing for the web are useless when developing for email clients. This has caused me an enormous amount of frustration, so I thought I would ask a question that would hopefully surface the best practices and necessary considerations for others like myself who may find themselves designing for gmail, outlook, etc. from time to time. Example: <style>...</style> vs inline CSS. In short: what transfers over from the web-world to the email-world, and what doesn't.

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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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  • Browser Preview Utility

    - by just_wes
    Hello everybody, Are there any programs that render websites from the point of view of different browsers? In other words, I'd like to be able to open and view websites as if it were Internet Explorer, Firefox, Chrome, Safari, etc. It would be a bonus if the utility has a paned interface that lets you view pages side by side. Thanks!

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  • Best datastructure for frequently queried list of objects

    - by panzerschreck
    Hello, I have a list of objects say, List. The Entity class has an equals method,on few attributes ( business rule ) to differentiate one Entity object from the other. The task that we usually carry out on this list is to remove all the duplicates something like this : List<Entity> noDuplicates = new ArrayList<Entity>(); for(Entity entity: lstEntities) { int indexOf = noDuplicates.indexOf(entity); if(indexOf >= 0 ) { noDuplicates.get(indexOf).merge(entity); } else { noDuplicates.add(entity); } } Now, the problem that I have been observing is that this part of the code, is slowing down considerably as soon as the list has objects more than 10000.I understand arraylist is doing a o(N) search. Is there a faster alternative, using HashMap is not an option, because the entity's uniqueness is built upon 4 of its attributes together, it would be tedious to put in the key itself into the map ? will sorted set help in faster querying ? Thanks

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  • ASP.NET MVC Filters: How to set Viewdata for Dropdown based on action paramter

    - by CRice
    Hi, Im loading an entity 'Member' from its id in route data. [ListItemsForMembershipType(true)] public ActionResult Edit(Member someMember) {...} The attribute on the action loads the membership type list items for a dropdown box and sticks it in viewdata. This is fine for add forms, and search forms (it gets all active items) but I need the attribute to execute BASED ON THE VALUE someMember.MembershipTypeId, because its current value must always be present when loading the item (i.e. all active items, plus the one from the loaded record). So the question is, what is the standard pattern for this? How can my attribute accept the value or should I be loading the viewdata for the drop down in a controller supertype or during model binding or something else? It is in an attribute now because the code to set the viewdata would otherwise be duplicated in each usage in each action.

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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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  • Generic Abstract Singleton with Custom Constructor in C#

    - by Heka
    I want to write a generic singleton with an external constructor. In other words the constructor can be modified. I have 2 designs in my mind but I don't know whether they are practical or not. First one is to enforce derived class' constructor to be non-public but I do not know if there is a way of it? Second one is to use a delegate and call it inside the constructor? It isn't necessarily to be a constructor. The reason I chose custom constructor is doing some custom initializations. Any suggestions would be appreciated :)

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  • What Is Utility Services ?

    - by query_bug
    Hai, I need some information about Utility Services Layer. Can someone Please help me in getting information on that as I am supposed to give a presentation on Utility Services Layer. Thanks in advance...

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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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  • Is it possible to write a database view that encompasses one-to-many relationships?

    - by Brandon Linton
    So I'm not necessarily saying this is even a good idea if it were possible, since the schema of the view would be extremely volatile, but is there any way to represent a has-many relationship in a single view? For example, let's say I have a customer that can have any number of addresses in the database. Is there any way to list out each column of each address with perhaps a number as a part of the alias (e.g., columns like Customer Id, Name, Address_Street_1, Address_Street_2, etc)? Thanks!

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  • Architecture of a single-page JavaScript web application?

    - by fig-gnuton
    How should a complex single-page JS web application be structured on the client-side? Specifically I'm curious about how to cleanly structure the application in terms of its model objects, UI components, any controllers, and objects handling server persistence. MVC seemed like a fit at first. But with UI components nested at various depths (each with their own way of acting on/reacting to model data, and each generating events which they themselves may or may not handle directly), it doesn't seem like MVC can be cleanly applied. (But please correct me if that's not the case.) -- (This question resulted in two suggestions of using ajax, which is obviously needed for anything other than the most trivial one-page app.)

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  • Javascript libraries + JQuery plugins contradict? How to debug?

    - by Metafaniel
    This is somewhat a newbie question... I effort everyday to learn, so please understand ;) I'm not the very best expert, but I can do a decent job good looking and functional websites or web applications. My main tools are PHP5, HTML5, CSS2 y 3, a database (SQLite, MySQL) and Javascript and JQuery. I'm not an expert at all in Javascript. I often find interesting JQuery plugins or tutorials and try to mix them up to do the functionality needed. This time I'm mixing maybe too much plugins and js files from different sources. In fact, my app do what I want except for certain behaviors... There are no errors, everything looks fine, but the misbehavior persists. So maybe I need to specify a class I don't know about, or one contradicts another one from another plugin and I just can't understand, for example, why a <button type="button">DON'T submit</button> just submits the form... Anyway, my point is: Do you people know a way to debug this situations??? Is there a generic tool, suggestion, workflow or something to help me understand conflicts or omissions between libraries or plugins??? (Javascript libraries, my own Javascripts and JQuery plugins)??? I hope it is a way! THANKS A LOT FOR YOUR HELP AND COMPREHENSION! =)

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