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• Finding changes in MongoDB database

  - by Jonathan Knight

  I'm designing a MongoDB database that works with a script that periodically polls a resource and gets back a response which is stored in the database. Right now my database has one collection with four fields , id, name, timestamp and data. I need to be able to find out which names had changes in the data field between script runs, and which did not. In pseudocode, if(data[name][timestamp]==data[name][timestamp+1]) //data has not changed store data in collection 1 else //data has changed between script runs for this name store data in collection 2 Is there a query that can do this without iterating and running javascript over each item in the collection? There are millions of documents, so this would be pretty slow. Should I create a new collection named timestamp for every time the script runs? Would that make it faster/more organized? Is there a better schema that could be used? The script runs once a day so I won't run into a namespace limitation any time soon.

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• actionscript-3: refactor interface inheritance to get rid of ambiguous reference error

  - by maxmc

  hi! imagine there are two interfaces arranged via composite pattern, one of them has a dispose method among other methods: interface IComponent extends ILeaf { ... function dispose() : void; } interface ILeaf { ... } some implementations have some more things in common (say an id) so there are two more interfaces: interface ICommonLeaf extends ILeaf { function get id() : String; } interface ICommonComponent extends ICommonLeaf, IComponent { } so far so good. but there is another interface which also has a dispose method: interface ISomething { ... function dispose() : void; } and ISomething is inherited by ICommonLeaf: interface ICommonLeaf extends ILeaf, ISomething { function get id() : String; } As soon as the dispose method is invoked on an instance which implements the ICommonComponent interface, the compiler fails with an ambiguous reference error because ISomething has a method called dispose and ILeaf also has a dispose method, both living in different interfaces (IComponent, ISomething) within the inheritace tree of ICommonComponent. I wonder how to deal with the situation if the IComponent, the ILeaf and the ISomething can't change. the composite structure must also work for for the ICommonLeaf & ICommonComponent implementations and the ICommonLeaf & ICommonComponent must conform to the ISomething type. this might be an actionscript-3 specific issue. i haven't tested how other languages (for instance java) handle stuff like this.

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• Can anyone explain how the Strategy Pattern relates to Inversion of Control?

  - by Shane

  Can anyone explain exactly how the Strategy Pattern relates to Inversion of Control?

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• Fowler Analysis Patterns lately?

  - by Berryl

  As much as I've always loved this one is how much I always wished there were more meaty examples of how to apply some of the concepts available. Is anyone aware of anything out there worth looking at that attempts to that? Cheers, Berryl

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• Help required in adding new methods, properties into existing classes dynamically

  - by Bepenfriends

  Hi All, I am not sure whether it is possible to achieve this kind of implementation in Dot Net. Below are the information Currently we are on an application which is done in COM+, ASP, XSL, XML technologies. It is a multi tier architecture application in which COM+ acts as the BAL. The execution steps for any CRUD operation will be defined using a seperate UI which uses XML to store the information. BAL reads the XML and understands the execution steps which are defined and executes corresponding methods in DLL. Much like EDM we have our custom model (using XML) which determines which property of object is searchable, retrievable etc. Based on this information BAL constructs queries and calls procedures to get the data. In the current application both BAL and DAL are heavily customizable without doing any code change. the results will be transmitted to presentation layer in XML format which constructs the UI based on the data recieved. Now I am creating a migration project which deals with employee information. It is also going to follow the N Tier architecture in which the presentation layer communicates with BAL which connects to DAL to return the Data. Here is the problem, In our existing version we are handling every information as XML in its native form (no converstion of object etc), but in the migration project, Team is really interested in utilizing the OOP model of development where every information which is sent from BAL need to be converted to objects of its respective types (example employeeCollection, Address Collection etc). If we have the static number of data returned from BAL we can have a class which contains those nodes as properties and we can access the same. But in our case the data returned from our BAL need to be customized. How can we handle the customization in presentation layer which is converting the result to an Object. Below is an example of the XML returned <employees> <employee> <firstName>Employee 1 First Name</firstName> <lastName>Employee 1 Last Name</lastName> <addresses> <address> <addressType>1</addressType> <StreetName>Street name1</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>2</addressType> <StreetName>Street name2</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>3</addressType> <StreetName>Street name3</StreetName> <RegionName>Region name</RegionName> <address> <addresses> </employee> <employee> <firstName>Employee 2 First Name</firstName> <lastName>Employee 2 Last Name</lastName> <addresses> <address> <addressType>1</addressType> <StreetName>Street name1</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>2</addressType> <StreetName>Street name2</StreetName> <RegionName>Region name</RegionName> <address> <addresses> </employee> </employees> If these are the only columns then i can write a class which is like public class Address{ public int AddressType {get;set;}; public string StreetName {get;set;}; public string RegionName {get;set;}; } public class Employee{ public string FirstName {get; set;} public string LastName {get; set;} public string AddressCollection {get; set;} } public class EmployeeCollection : List<Employee>{ public bool Add (Employee Data){ .... } } public class AddressCollection : List<Address>{ public bool Add (Address Data){ .... } } This class will be provided to customers and consultants as DLLs. We will not provide the source code for the same. Now when the consultants or customers does customization(example adding country to address and adding passport information object with employee object) they must be able to access those properties in these classes, but without source code they will not be able to do those modifications.which makes the application useless. Is there is any way to acomplish this in DotNet. I thought of using Anonymous classes but, the problem with Anonymous classes are we can not have methods in it. I am not sure how can i fit the collection objects (which will be inturn an anonymous class) Not sure about datagrid / user control binding etc. I also thought of using CODEDom to create classes runtime but not sure about the meory, performance issues. also the classes must be created only once and must use the same till there is another change. Kindly help me out in this problem. Any kind of help meterial/ cryptic code/ links will be helpful.

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• How to find good looking font color if background color is known?

  - by Mecki

  There seem to be so many color wheel, color picker, and color matcher web apps out there, where you give one color and the they'll find a couple of other colors that will create a harmonic layout when being used in combination. However most of them focus on background colors only and any text printed on each background color (if text is printed at all in the preview) is either black or white. My problem is different. I know the background color I want to use for a text area. What I need help with is choosing a couple of colors (the more, the merrier) I can use as font colors on this background. Most important is that the color will make sure the font is readable (contrast not being too low, also maybe not being too high to avoid that eyes are stressed) and of course that the combination of foreground and background just looks good. Anyone being aware of such an application? I'd prefer a web application to anything I have to download. Thanks.

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• Learning Modelling

  - by me1234

  Is there a good book which I can follow to learn modelling/doing architecture? Good samples? What would you do if you have to learn modelling from very basics? Thanks

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• Back Orders for ERP: data model references ?

  - by Patrick Honorez

  I have built an ERP using Sql Server as a back-end. These are the different types of Client documents (there are also Supplier Docs): Order -- impact: BO Delivery Note (also used for returns, with negative quantity) --impact: BO, Stock Invoice --impact: accounting only Credit Note --impact: accounting, BO I use a complex system of self joins (at detail level) to find out the quantities in each OrderDetail that still have a backorder (BO). It'd like to simplify this using a [group] field that could be used through all detail line related to an original order. There are many difficult things to trace: a Return of a product may be due to a defect and thus increase the BO, or it can be just a return, joined with a Credit Note, and then has no impact on BO. My question is: do you know of any real good reference (book, web) for this matter ?

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• How to Prove that using subselect queries in SQL is killing performance of server

  - by adopilot

  One of my jobs it to maintain our database, usually we have troubles with lack of performance while getting reports and working whit that base. When I start looking at queries which our ERP sending to database I see a lot of totally needlessly subselect queries inside main queries. As I am not member of developers which is creator of program we using, they do not like much when I criticize they code and job. Let say they do not taking my review as serious statements. So I asking you few questions about subselect in SQL Does subselect is taking a lot of more time then left outer joins? Does exists any blog, article or anything where I subselect is recommended not to use ? How I can prove that if we avoid subselesct in query that query is going to be faster ? Our database server is MSSQL2005

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• Is Form validation and Business validation too much?

  - by Robert Cabri

  I've got this question about form validation and business validation. I see a lot of frameworks that use some sort of form validation library. You submit some values and the library validates the values from the form. If not ok it will show some errors on you screen. If all goes to plan the values will be set into domain objects. Here the values will be or, better said, should validated (again). Most likely the same validation in the validation library. I know 2 PHP frameworks having this kind of construction Zend/Kohana. When I look at programming and some principles like Don't Repeat Yourself (DRY) and single responsibility principle (SRP) this isn't a good way. As you can see it validates twice. Why not create domain objects that do the actual validation. Example: Form with username and email form is submitted. Values of the username field and the email field will be populated in 2 different Domain objects: Username and Email class Username {} class Email {} These objects validate their data and if not valid throw an exception. Do you agree? What do you think about this aproach? Is there a better way to implement validations? I'm confused about a lot of frameworks/developers handling this stuff. Are they all wrong or am I missing a point? Edit: I know there should also be client side kind of validation. This is a different ballgame in my Opinion. If You have some comments on this and a way to deal with this kind of stuff, please provide.

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• mysql and trigger usage question

  - by dhruvbird

  I have a situation in which I don't want inserts to take place (the transaction should rollback) if a certain condition is met. I could write this logic in the application code, but say for some reason, it has to be written in MySQL itself (say clients written in different languages will be inserting into this MySQL InnoDB table) [that's a separate discussion]. Table definition: CREATE TABLE table1(x int NOT NULL); The trigger looks something like this: CREATE TRIGGER t1 BEFORE INSERT ON table1 FOR EACH ROW IF (condition) THEN NEW.x = NULL; END IF; END; I am guessing it could also be written as(untested): CREATE TRIGGER t1 BEFORE INSERT ON table1 FOR EACH ROW IF (condition) THEN ROLLBACK; END IF; END; But, this doesn't work: CREATE TRIGGER t1 BEFORE INSERT ON table1 ROLLBACK; You are guaranteed that: Your DB will always be MySQL Table type will always be InnoDB That NOT NULL column will always stay the way it is Question: Do you see anything objectionable in the 1st method?

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• Given a trace of packets, how would you group them into flows?

  - by zxcvbnm

  I've tried it these ways so far: 1) Make a hash with the source IP/port and destination IP/port as keys. Each position in the hash is a list of packets. The hash is then saved in a file, with each flow separated by some special characters/line. Problem: Not enough memory for large traces. 2) Make a hash with the same key as above, but only keep in memory the file handles. Each packet is then put into the hash[key] that points to the right file. Problems: Too many flows/files (~200k) and it might run out of memory as well. 3) Hash the source IP/port and destination IP/port, then put the info inside a file. The difference between 2 and 3 is that here the files are opened and closed for each operation, so I don't have to worry about running out of memory because I opened too many at the same time. Problems: WAY too slow, same number of files as 2 so also impractical. 4) Make a hash of the source IP/port pairs and then iterate over the whole trace for each flow. Take the packets that are part of that flow and place them into the output file. Problem: Suppose I have a 60 MB trace that has 200k flows. This way, I would process, say, a 60 MB file 200k times. Maybe removing the packets as I iterate would make it not so painful, but so far I'm not sure this would be a good solution. 5) Split them by IP source/destination and then create a single file for each one, separating the flows by special characters. Still too many files (+50k). Right now I'm using Ruby to do it, which might've been a bad idea, I guess. Currently I've filtered the traces with tshark so that they only have relevant info, so I can't really make them any smaller. I thought about loading everything in memory as described in 1) using C#/Java/C++, but I was wondering if there wouldn't be a better approach here, especially since I might also run out of memory later on even with a more efficient language if I have to use larger traces. In summary, the problem I'm facing is that I either have too many files or that I run out of memory. I've also tried searching for some tool to filter the info, but I don't think there is one. The ones I've found only return some statistics and wouldn't scan for every flow as I need.

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• Any tips of how to handle hierarchical trees in relational model?

  - by George

  Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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• Need to work out database structure

  - by jim smith

  Hi, Just need a little kickstart with this. I have Mysql/PHP, and I have 5,000 products. I have 30 companies I need to store some data for those 30 companies for each product as follows: a) prices b) stock qty I also need to store data historically on a daily basis. So the table... It makes sense that the records will be the products because there's 5000, and if I put the companies as the columns, I can store the prices, but what about the stock quantities? I could create two columns for each compoany, one for prices, one for qty. Then make the tablename the date for that day...so theer would be a new table for every day with 5000 products in it? is this the correct way? Some idea on how I'll be retreiving data the top 5 lowest prices (and the company) by product for a certain date the price and stock changes in the past 7 days by product

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• ASP.NET sets of technologies/components

  - by Maxim Gueivandov

  Just a question of pure curiosity. It happens that development teams tend to stick to the same technological set(s) for some time, for various reasons (obviously, the lack of time, money, necessity and/or willingless to adopt new technologies). So, what are your usual sets of technologies/components to build an ASP.NET application (e.g., WebForms / MVC, Automapper, NInject, NHibernate / LinqToSql, JQuery / ASP.NET Ajax, ...) or architectural frameworks (Arch#, Catharsis, ...) and in which context do you use them (site size, speed/availability requirements, etc.)?

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• best option to create simple website mockup with navigation

  - by Buzzer

  I'm trying to put together a static html website with full navigation. In other words, I want the user to click some links and images and actually be taken to another page. I'm a developer so I know how to do this in frameworks like ASP.Net MVC and grails. However, for this particular case, I just want to quickly mock up the UI and provide simple navigation so I can do some user testing. Can anyone advice on how to do this? Thanks,

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• Google Calendar like interface

  - by John Virgolino

  I need to write an application that essentially functions like a week-view of a calendar, columns for the days and then rows for appointments. Where the height of the appointment box visually represents time. In my case, I just don't want the time of day as the vertical axis, I just want hours or mins. The Google AJAX approach is very clean and easy to use and would be perfect, I think, but my major knowledge comes in ASP.Net and Windows Forms (.Net). I don't want to reinvent the wheel, but I find my mind is stuck on this problem and that I would have to create an interface from scratch for this. I have checked out the Infragistics product (used it for other projects) and read up a lot on the Google API's including their Ajax toolkit. I haven't done Java, however learning a language is not my issue, it's learning the particulars that will help me reach my goal that I feel will take most of the time. Am I making a mountain out of a mole hill? Is this really a lot easier than I think? This is starting to sound like a Dear Abby post - I'll stop now. Any advice or insight would be great! Thanks all!

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• Natural vs surrogate keys on support tables

  - by Bugeo

  I have read many articles about the battle between natural versus surrogate primary keys. I agree in the use of surrogate keys to identify records of tables whose contents are created by the user. But in the case of supporting tables what should I use? For example, in a hypothetical table "orderStates". If you use a natural key would have the following data: TABLE ORDERSTATES {ID: "NEW", NAME: "New"} {ID: "MANAGEMENT" NAME: "Management"} {ID: "SHIPPED" NAME: "Shipped"} If I use a surrogate key would have the following data: TABLE ORDERSTATES {ID: 1 CODE: "NEW", NAME: "New"} {ID: 2 CODE: "MANAGEMENT" NAME: "Management"} {ID: 3 CODE: "SHIPPED" NAME: "Shipped"} Now let's take an example: a user enters a new order. In the case in which use natural keys, in the code I can write this: newOrder.StateOrderId = "NEW"; With the surrogate keys instead every time I have an additional step. stateOrderId_NEW = .... I retrieve the id corresponding to the recod code "NEW" newOrder.StateOrderId = stateOrderId_NEW; The same will happen every time I have to move the order in a new status. So, in this case, what are the reason to chose one key type vs the other one?

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• In Ruby, can the coerce() method know what operator it is that requires the help to coerce?

  - by Jian Lin

  In Ruby, it seems that a lot of coerce() help can be done by def coerce(something) [self, something] end that's is, when 3 + rational is needed, Fixnum 3 doesn't know how to handle adding a Rational, so it asks Rational#coerce for help by calling rational.coerce(3), and this coerce instance method will tell the caller: # I know how to handle rational + something, so I will return you the following: [self, something] # so that now you can invoke + on me, and I will deal with Fixnum to get an answer So what if most operators can use this method, but not when it is (a - b) != (b - a) situation? Can coerce() know which operator it is, and just handle those special cases, while just using the simple [self, something] to handle all the other cases where (a op b) == (b op a) ? (op is the operator).

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• Practical rules for premature optimization

  - by DougW

  It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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• What is an index in MySQL?

  - by Eric

  http://i.imgur.com/JdsUK.jpg I created a table like the picture above. What are the "Indexes"? primary key? unique? It works well without setting indexes.. What do they do? why do I need them? Also, I set all String fields to TEXT because I didn't know how many characters I need. Is this a good idea? I don't see any difference. Thanks!

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• Repoer Designer for vb.net using Visual Studio 2008 and a SQL 2005 back end database other than Crys

  - by GaryBrown

  We are developing in vb.net using Visual Studio 2008 and a SQL 2005 back end database and are looking for a Report Designer that can be used to build reports and give the User the ability to modify and create reports once the software is sold and in use.

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• Using Doctrine to abstract CRUD operations

  - by TomWilsonFL

  This has bothered me for quite a while, but now it is necessity that I find the answer. We are working on quite a large project using CodeIgniter plus Doctrine. Our application has a front end and also an admin area for the company to check/change/delete data. When we designed the front end, we simply consumed most of the Doctrine code right in the controller: //In semi-pseudocode function register() { $data = get_post_data(); if (count($data) && isValid($data)) { $U = new User(); $U->fromArray($data); $U->save(); $C = new Customer(); $C->fromArray($data); $C->user_id = $U->id; $C->save(); redirect_to_next_step(); } } Obviously when we went to do the admin views code duplication began and considering we were in a "get it DONE" mode so it now stinks with code bloat. I have moved a lot of functionality (business logic) into the model using model methods, but the basic CRUD does not fit there. I was going to attempt to place the CRUD into static methods, i.e. Customer::save($array) [would perform both insert and update depending on if prikey is present in array], Customer::delete($id), Customer::getObj($id = false) [if false, get all data]. This is going to become painful though for 32 model objects (and growing). Also, at times models need to interact (as the interaction above between user data and customer data), which can't be done in a static method without breaking encapsulation. I envision adding another layer to this (exposing web services), so knowing there are going to be 3 "controllers" at some point I need to encapsulate this CRUD somewhere (obviously), but are static methods the way to go, or is there another road? Your input is much appreciated.

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• Twitter Bootstrap Collapsible Navbar Duplicating

  - by sixeightzero

  I am working on a project using Twitter Bootstrap. One thing that I noticed is that my pages have duplicate navbars when they are defined as collapsible and the page is resized smaller. Here is the duplicate NavBar: Here is the normal width NavBar: Code: <!DOCTYPE html> <html lang="en"> <!--[if lt IE 7]> <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]--> <!--[if IE 7]> <html class="no-js lt-ie9 lt-ie8"> <![endif]--> <!--[if IE 8]> <html class="no-js lt-ie9"> <![endif]--> <!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]--> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <title></title> <meta name="description" content=""> <meta name="viewport" content="width=device-width"> <link rel="stylesheet" href="/assets/css/bootstrap.css"> <style> body { padding-top: 60px; } </style> <link rel="stylesheet" href="/assets/css/bootstrap-responsive.min.css"> <link rel="stylesheet" href="/assets/css/main.css"> <script>window.jQuery || document.write('<script src="/assets/js/vendor/jquery-1.8.1.min.js"><\/script>')</script> <script src="/assets/js/vendor/modernizr-2.6.1-respond-1.1.0.min.js"></script> </head> <body class="dark"> <!--[if lt IE 9]> <p class="chromeframe">You are using an outdated browser. <a href="http://browsehappy.com/">Upgrade your browser today</a> or <a href="http://www.google.com/chromeframe/?redirect=true">install Google Chrome Frame</a> to better experience this site.</p> <![endif]--> <div class="navbar navbar-inverse navbar-fixed-top"> <div class="navbar-inner"> <div class="container"> <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse"> <span class="icon-bar"></span> <span class="icon-bar"></span> <span class="icon-bar"></span> </a> <a class="brand" href="#">Project name</a> <div class="nav-collapse collapse"> <ul class="nav"> <li class="active"><a href="#">Home</a></li> <li><a href="#about">About</a></li> <li><a href="#contact">Contact</a></li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <b class="caret"></b></a> <ul class="dropdown-menu"> <li><a href="#">Action</a></li> <li><a href="#">Another action</a></li> <li><a href="#">Something else here</a></li> <li class="divider"></li> <li class="nav-header">Nav header</li> <li><a href="#">Separated link</a></li> <li><a href="#">One more separated link</a></li> </ul> </li> </ul> </div><!--/.nav-collapse --> </div> </div> </div> Has anyone else run into this and have some pointers?

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• Architectural decision : QT or Eclipse Platform ?

  - by umanga

  We are in the process of designing a tool to be used with HDEM(High Definition Electron Microscope).We get stacks of 2D images from HDEM and first step is 'detecting borders' on the sections.After detecting edges of 2D slices ,next step is construct the 3D model using these 2D slices. This 'border detecting' algorithm(s) is/are implemented by one of professor and he has used and suggests to use C.(to gain high performance and probably will parallelise in future) We have to develop comprehensive UI ,3D viewer ,2D editor...etc and use this algorithm. Application should support usual features like project save/open.Undo,Redo...etc Our technology decisions are: A) Build entire platform from the scratch using QT. B) Use Eclipse Platform Our concerns are, if we choose A) we can easily integrate the 'border detecting' algorithm(s) because the development environment is C/C++ But we have to implement the basic features from the scratch. If we choose B) we get basic features from the Eclipse platform , but integrating C libraries going to be a tedious task. Any suggestions on this?

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