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• C++ visitor pattern handling templated string types?

  - by Steve the Plant

  I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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• If we make a number every millisecond, how much data would we have in a day?

  - by Roger Travis

  I'm a bit confused here... I'm being offered to get into a project, where would be an array of certain sensors, that would give off reading every millisecond ( yes, 1000 reading in a second ). Reading would be a 3 or 4 digit number, for example like 818 or 1529. This reading need to be stored in a database on a server and accessed remotely. I never worked with such big amounts of data, what do you think, how much in terms of MBs reading from one sensor for a day would be?... 4(digits)x1000x60x60x24 ... = 345600000 bits ... right ? about 42 MB per day... doesn't seem too bad, right? therefor a DB of, say, 1 GB, would hold 23 days of info from 1 sensor, correct? I understand that MySQL & PHP probably would not be able to handle it... what would you suggest, maybe some aps? azure? oracle? ... Thansk!

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• Storing users in a database

  - by EMcKenna

  Im wondering whats the best way of storing different types of users in my database. I am writing an application that has 4 main user types (admin, school, teacher, student). At the moment I have a table for each of these but i'm not sure thats the best way of storing user information. For instance... Allowing students to PM other student is simple (store sender and receiver student_id) but enabling teachers to PM students requires another table (sender teacher_id, sender student_id). Should all users be stored in one users table with a user_type field? If so, the teacher / student specific information will still have to be stored in another table. users user_id, password_hash, user_type students user_id, student_specific_stuff... teachers user_id, teacher_specific_stuff... How do I stop a user who has a user_type = student from being accidentally being entered into the teachers table (as both have a user_id) Just want to make sure I get the database correct before i go any further. Thanks...

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• What performance overhead do IoC containers involve?

  - by Sosh

  Hi, Loose coupling is wonderful of course, but I have often wondered what overhead wiring up dynamically using an IoC container (for example Castle Windsor) has over a tightly coupled system? I know that a detailed answer would depend on what the IoC was being used for, but I'm really just trying to get a feel for the magnitude of effort involved in the IoC work. Does anyone have any stats or other resources regarding this? Thanks

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• PHP Frontpage/Page controller

  - by atno

  I using the following as Frontpage/Page Controller(s) and it's working ok so far, except two problems I'm facing which as you can see are the $pages array and the switch, which are actually much much longer as the one I've pasted here. Everytime there is a need for a new page controller I have to add it to $pages array and to switch which makes that list very long. How would you overcome this problem and do you see any other improvement on this code? loadLogic() in page controllers it is used to get functions under pages/controllername/logic/function.php. Frontpage Controller - index.php: include 'common/common.php'; if(!isset($_GET['p']) OR $_GET['p'] == ''){ $_GET['p'] = 'home'; header('Location: index.php?p=home'); } $pages = array('home','register','login','logout','page1','page2','page3'); $_GET['p'] = trim($_GET['p']); if(isset($_GET['p'])){ if(in_array($_GET['p'], $pages)){ switch ($_GET['p']) { case 'home': include 'home.php'; break; case 'register': include 'register.php'; break; case 'login': include 'login.php'; break; case 'logout': include 'logout.php'; break; case 'page1': include 'page1.php'; break; case 'page2': include 'page2.php'; break; case 'page3': include 'page3.php'; break; } }else{ echo '404!'; } } Page Controller - {home,register,login,logout,page1,page2,page3}.php: include 'tpl/common/header.php'; contentStart(); if(isset($_SESSION['logged'])){ loadLogic('dashboard'); }else{ loadLogic('nologin'); } //Display login form in logic page instead links // if(!isset($_SESSION['logged'])){ contentEnd(); loadLogic('nologinForm'); }else{ contentEnd(); include'tpl/common/rcol.php'; } include 'tpl/common/footer.php'; function loadLogic(): function loadLogic($logic) { $path = dirname(__DIR__) . '/pages'; $controller = preg_split('/&/',$_SERVER['QUERY_STRING']); $controller = trim($controller[0],"p="); $logicPath = 'logic'; $logic = $logic . '.php'; $err = 0; $logicFullPath = $path.'/'.$controller.'/'.$logicPath.'/'.$logic; if($err == '0'){ include "$logicFullPath"; } } Folder Structure: projectName | ---> common | ---> pages | | | --->home | | | --->register | | | --->login | | | --->logout | | | --->page1 | | | --->page2 | | | --->page3 | ---> tpl | | | ---> common | --> home.php | --> register.php | --> login.php | --> logout.php | --> page1.php | --> page2.php | --> page3.php

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• How much does a Creative Director charge hourly?

  - by user295292

  How much does a Senior level Creative Director charge hourly for a project?

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• When using a HiLo ID generation strategy, what types should be used to hold Ids?

  - by UpTheCreek

  I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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• Would ViewModels fit in the Model View Presenter pattern?

  - by Jonn

  Having used ViewModels in MVC, I was wondering if applying the same to the MVP pattern is practical. I only have a few considerations, one being that MVP is already fairly hard to implement (with all the additional coding, not much on the seeming complexity) or that ViewModels already have a slightly similar way of modeling data or entities. Would adding another layer in the form of ViewModels be redundant or is it a logical abstraction that I, as one implementing the MVP pattern, should adhere to?

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• Haskell: Pattern Matching with Lists

  - by user1670032

  I'm trying to make a function that takes in a list, and if one of the elements is negative, then any elements in that list that are equal to its positive counterpart should be changed to 0. Eg, if there is a -2 in a list, then all 2's in that list should be changed to 0. Any ideas why it only works for some cases and not others? I'm not understanding why this is, I've looked it over several times. changeToZero [] = [] changeToZero [x] = [x] changeToZero (x:zs:y:ws) | (x < 0) && ((-1)*(x) == y) = x : zs : 0 : changeToZero ws changeToZero (x:xs) = x : changeToZero xs *Main changeToZero [-1,1,-2,2,-3,3] [-1,1,-2,2,-3,3] *Main changeToZero [-2,1,2,3] [-2,1,0,3] *Main changeToZero [-2,1,2,3,2] [-2,1,0,3,2] *Main changeToZero [1,-2,2,2,1] [1,-2,2,0,1]

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• Why didn't C have a boolean data type prior to C99?

  - by frou

  I realise you can just #define some integers, but why didn't C have a dedicated boolean data type before C99? It's such a common occurence in programming and logic, I don't understand the absense of an explicit type and notation.

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• Pattern for null settings

  - by user21243

  Hi, I would like to hear your thoughts and ideas about this one. in my application i have controls that are binded to objects properties. but.. the controls always looks like that: a check box, label that explain the settings and then the edited control (for ex: text box) when unchecking the checkbox i disable the text box (using binding) when the checkbox is unchecked i want the property to contain null, and when it is checked i would like the property to contain the text box's text. Of course text box can be NumericUpDown, ComboBox, DatePicker etc.. Do you have any smart way of doing it using binding or do i have to do everything on code; I really would like to a build a control that supports that and re-use it all over Ideas? Thanks,

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• Passing an array for setting variable

  - by mathk

  Hi, I often see this idiom when reading php code: public function __construct($config) { if (array_key_exists('options', $config)) { ... } if (array_key_exists('driver_options', $config)) { ... } } Here I am concern with the way the parameter is used. If I were in lisp I would do: (defun ct (&key options driver_options) (do-something-with-option-and-driver_option)) But since I am in PHP I would rather have a constructor that take a list of parameter and let them be null if there a not require. So what do you guys think about having an array as parameter in other to do some initialization-or-whatever? In other to answer you have to take in account the point of view of the user of the function and the designer of the API. Also have you ever heard this has a code-smell? thanks

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• Getters and Setters: Code smell, Necessary Evil, or Can't Live Without Them [closed]

  - by Avery Payne

  Possible Duplicate: Allen Holub wrote “You should never use get/set functions”, is he correct? Is there a good, no, a very good reason, to go through all the trouble of using getters and setters for object-oriented languages? What's wrong with just using a direct reference to a property or method? Is there some kind of "semantical coverup" that people don't want to talk about in polite company? Was I just too tired and fell asleep when someone walked out and said "Thou Shalt Write Copious Amounts of Code to Obtain Getters and Setters"? Follow-up after a year: It seems to be a common occurrence with Java, less so with Python. I'm beginning to wonder if this is more of a cultural phenomena (related to the limitations of the language) rather than "sage advice". The -1 question score is complete for-the-lulz as far as I am concerned. It's interesting that there are specific questions that are downvoted, not because they are "bad questions", but rather, because they hit someone's raw nerve.

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• Join Where Rows Don't Exist or Where Criteria Matches...?

  - by Greg

  I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of Unions. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid Order: OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI Promo: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 PromoPackage: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 Desired Result: OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0

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• Circular dependency with generics

  - by devoured elysium

  I have defined the following interface: public interface IStateSpace<State, Action> where State : IState where Action : IAction<State, Action> // <-- this is the line that bothers me { void SetValueAt(State state, Action action); Action GetValueAt(State state); } Basically, an IStateSpace interface should be something like a chess board, and in each position of the chess board you have a set of possible movements to do. Those movements here are called IActions. I have defined this interface this way so I can accommodate for different implementations: I can then define concrete classes that implement 2D matrix, 3D matrix, graphs, etc. public interface IAction<State, Action> { IStateSpace<State, Action> StateSpace { get; } } An IAction, would be to move up(this is, if in (2, 2) move to (2, 1)), move down, etc. Now, I'll want that each action has access to a StateSpace so it can do some checking logic. Is this implementation correct? Or is this a bad case of a circular dependence? If yes, how to accomplish "the same" in a different way? Thanks

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• Why should GoTos be bad?

  - by lisn

  I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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• Handling Dialogs in WPF with MVVM

  - by Ray Booysen

  In the MVVM pattern for WPF, handling dialogs is one of the more complex operations. As your view model does not know anything about the view, dialog communication can be interesting. I can expose an ICommand that when the view invokes it, a dialog can appear. Does anyone know of a good way to handle results from dialogs? I am speaking about windows dialogs such as MessageBox. One of the ways we did this was have an event on the viewmodel that the view would subscribe to when a dialog was required. public event EventHandler<MyDeleteArgs> RequiresDeleteDialog; This is OK, but it means that the view requires code which is something I would like to stay away from.

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• Base class with abstract subclasses in C# ?

  - by Nick Brooks

  public abstract class Request { public class Parameters { //Threre are no members here //But there should be in inherited classes } public Request() { parameters = new Parameters(); } public Parameters parameters; } Two questions: How do I make it so I can add stuff to the constructor but the original constructor will still be executed? How do I make it so the subclasses can add members to the Parameters class?

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• Refactoring tools for namespaces and physical project structure

  - by simendsjo

  When I hack around, some code tend to get much bigger than originally planned. As this happens I usually introduce/collapse/merge namespaces, move files between them, move folders etc etc. Sometimes, if I don't have a clear picture of the end result, this is a real pain and really easy to just "skip". This leads the project deteriorate where classes belong elsewhere, strange namespaces, no folders/wrong folders etc. And then I usually cannot take it anymore and do a larger cleanup - which is usually not difficult, just very tedious and it feels nice to do everything at once, so I do a code freeze while finishing up. So my question is... Are there any tools to help refactoring the namespace/physical aspects of a project?

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• ASP.Net Architecture Specific to Shared/Static functions

  - by Maxim Gershkovich

  Hello All, Could someone please advise in the context of a ASP.Net application is a shared/static function common to all users? If for example you have a function Public shared function GetStockByID(StockID as Guid) as Stock Is that function common to all current users of your application? Or is the shared function only specific to the current user and shared in the context of ONLY that current user? So more specifically my question is this, besides database concurrency issues such as table locking do I need to concern myself with threading issues in shared functions in an ASP.Net application? In my head; let’s say my application namespace is MyTestApplicationNamespace. Everytime a new user connects to my site a new instance of the MyTestApplicationNamespace is created and therefore all shared functions are common to that instance and user but NOT common across multiple users. Is this correct?

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• Travelling Salesman Problem Constraint Representation

  - by alex25

  Hey! I read a couple of articles and sample code about how to solve TSP with Genetic Algorithms and Ant Colony Optimization etc. But everything I found didn't include time (window) constraints, eg. "I have to be at customer x before 12am)" and assumed symmetry. Can somebody point me into the direction of some sample code or articles that explain how I can add constraints to TSP and how I can represent those in code. Thanks!

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• Data Access Layer in ASP.Net: Where do I create the Connection?

  - by atticae

  If I want to create a 3-Layer ASP.Net application (Presentation Layer, Business Layer, Data Access Layer), where is the best place to create the Connection objects? So far I used a helper class in my Presentation Layer to create an IDbCommand from the ConnectionString in the web.config on each page and passed it on to the DAL classes/methods. Now I am not so sure, if this part shouldn't also be included in the DAL somehow, because it obviously is part of the Data Access. The DAL is in a separately compilated project, so I dont have access to the web.config and cannot access the connection string (right?). What is the best practice here?

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• Designing a frontend/backend architecture

  - by wrp

  What are some good information sources on designing programs with a client/server architecture? This is for development of a desktop application, not a Web service. The only books I have found on client/server apps deal with the case of a thin client connecting to a remote database. Two good examples of what I mean are Mathematica and SuperCollider. I'm looking for platform- and language-agnostic discussion of the issues in developing a frontend/backend system. Especially useful topics would be allocation of responsibilities and options for message passing.

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• how to elegantly duplicate a graph (neural network)

  - by macias

  I have a graph (network) which consists of layers, which contains nodes (neurons). I would like to write a procedure to duplicate entire graph in most elegant way possible -- i.e. with minimal or no overhead added to the structure of the node or layer. Or yet in other words -- the procedure could be complex, but the complexity should not "leak" to structures. They should be no complex just because they are copyable. I wrote the code in C#, so far it looks like this: neuron has additional field -- copy_of which is pointer the the neuron which base copied from, this is my additional overhead neuron has parameterless method Clone() neuron has method Reconnect() -- which exchanges connection from "source" neuron (parameter) to "target" neuron (parameter) layer has parameterless method Clone() -- it simply call Clone() for all neurons network has parameterless method Clone() -- it calls Clone() for every layer and then it iterates over all neurons and creates mappings neuron=copy_of and then calls Reconnect to exchange all the "wiring" I hope my approach is clear. The question is -- is there more elegant method, I particularly don't like keeping extra pointer in neuron class just in case of being copied! I would like to gather the data in one point (network's Clone) and then dispose it completely (Clone method cannot have an argument though).

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• HTML-like GUI Framework in Java

  - by wintermute

  I was recently brought onto a project where we are developing a lot GUI elements for BlackBerry devices. The standard RIM APIs are pretty basic, almost never do what is required and are difficult or impossible to extend, so we end up re-implementing chunks of it. Currently the code we have isn't super organized and factored so there are lots of little tricks that get implemented over and over again. I had a thought about how to aid development efforts on this platform and wanted to see if the community could tell me if I'm still sane or if I've gone totally nuts. By far, the biggest organizational problem I've run into is making sure that each screen is laid out properly with proper padding and such. The current approach is to manually keep track of padding like so: protected void sublayout(int width, int height) { final int padding = 5; int y = padding; int x = padding; layoutChild(_someChild, width - padding * 2, height / 3 - padding * 2); setPositionChild(_someChild, x, y); y += _someChild.getHeight() + padding; // Calculate where to start drawing next. /* ... snipped ... */ } As you can see, positioning elements on a screen is a nightmare due to the tedium. I have investigated other GUI frameworks but, for a variety of reasons, it is difficult to find one that suites our purposes. One potential solution that came to me is to create a GUI framework who's API resembles HTML/CSS. This would allow for things like padding, margins, borders and colours to be handled through a sort of CSS API while the content would be organized using the HTML part of the API. It might look something like this: public class OptionsScreen extends Document { public OptionsScreen() { // You would set the style (like CSS style) through the constructor. Div content = new Div(new Style(new Padding(5), Color.BLACK)); // Then build up a tree of elements which can each have their own style's. // Each element knows how to draw itself, but it doesn't have to worry about // manually handling things like padding. // content.addChild(new P("This is a paragraph", new Style(new Padding(), Color.RED))); Ul list = new Ul(); list.addChild(new Li("item 1")); list.addChild(new Li("item 2")); content.addChild(list); addChild(content); } } I can imagine this making it easier to customize the UI of our app (which is very important) with different fonts, colours and layouts. Does this idea belong on The Daily WTF or do you think there is some promise?

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