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• rake db:migrate fails when trying to do inserts

  - by anthony

  I'm trying to get a database populate so I can begin working on a project. THis project is already built and I'm being brought in to helpwith front-end work. Problem is I can't get rake db:migrate to do any inserts. Every time I run rake db:migrate I get this: ... == 20081220084043 CreateTimeDimension: migrating ============================== -- create_table(:time_dimension) - 0.0870s INSERT time_dimension(time_key, year, month, day, day_of_week, weekend, quarter) VALUES(20080101, 2008, 1, 1, 'Tuesday', false, 1) rake aborted! Could not load driver (uninitialized constant Mysql::Driver) ... I'm building on a MBP with Snow Leopard. I've installed XCode from the disk that comes with the mac. I've updated ruby, installed rails and all the needed gems. I have the 64 bit version of MySQL installed. I've tried the 32 bit version of MySQL and I've even tried installing from macports (via http://www.robbyonrails.com/articles/2010/02/08/installing-ruby-on-rails-passenger-postgresql-mysql-oh-my-zsh-on-snow-leopard-fourth-edition) The mysql gemis installed using: sudo env ARCHFLAGS="-arch x86_64" gem install mysql -- --with-mysql-config=/path/to/mysql/bin/mysql_config the migrate creates the tables just fine but it dies every. single. time. it trys an insert. Any help would be great

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• Using before_create in Rails to normalize a many to many table

  - by weotch

  I am working on a pretty standard tagging implementation for a table of recipes. There is a many to many relationship between recipes and tags so the tags table will be normalized. Here are my models: class Recipe < ActiveRecord::Base has_many :tag_joins, :as => :parent has_many :tags, :through => :tag_joins end class TagJoin < ActiveRecord::Base belongs_to :parent, :polymorphic => true belongs_to :tag, :counter_cache => :usage_count end class Tag < ActiveRecord::Base has_many :tag_joins, :as => :parent has_many :recipes, :through => :tag_joins, :source => :parent , :source_type => 'Recipe' before_create :normalizeTable def normalizeTable t = Tag.find_by_name(self.name) if (t) j = TagJoin.new j.parent_type = self.tag_joins.parent_type j.parent_id = self.tag_joins.parent_id j.tag_id = t.id return false end end end The last bit, the before_create callback, is what I'm trying to get working. My goal is if there is an attempt to create a new tag with the same name as one already in the table, only a single row in the join table is produced, using the existing row in tags. Currently the code dies with: undefined method `parent_type' for #<Class:0x102f5ce38> Any suggestions?

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• Query crashes MS Access

  - by user284651

  THE TASK: I am in the process of migrating a DB from MS Access to Maximizer. In order to do this I must take 64 tables in MS ACCESS and merge them into one. The output must be in the form of a TAB or CSV file. Which will then be imported into Maximizer. THE PROBLEM: Access is unable to perform a query that is so complex it seems, as it crashes any time I run the query. ALTERNATIVES: I have thought about a few alternatives, and would like to do the least time-consuming one, out of these, while also taking advantage of any opportunities to learn something new. Export each table into CSVs and import into SQLight and then make a query with it to do the same as what ACCESS fails to do (merge 64 tables). Export each table into CSVs and write a script to access each one and merge the CSVs into a single CSV. Somehow connect to the MS ACCESS DB (API), and write a script to pull data from each table and merge them into a CSV file. QUESTION: What do you recommend?

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• Modify php shopping cart to support multiple drop down menus

  - by Thomas

  I have a shopping cart script that I am trying to modify to support multiple product selection. As it is now, the customer can select a product from a single drop down menu. Now, I would like to add multiple dropdown menus (all populated with the same options). Here is the php that outputs the dropdown menu: if($eshopoptions['options_num']>1){ $opt=$eshopoptions['options_num']; $replace.="\n".'<label for="eopt'.$theid.'"><select id="eopt'.$theid.'" name="option">'; for($i=1;$i<=$opt;$i++){ $option=$eshop_product['products'][$i]['option']; $price=$eshop_product['products'][$i]['price']; if($option!=''){ if($price!='0.00') $replace.='<option value="'.$i.'">'.stripslashes(esc_attr($option)).' @ '.sprintf( _c('%1$s%2$s|1-currency symbol 2-amount','eshop'), $currsymbol, number_format($price,2)).'</option>'."\n"; else $replace.='<option value="'.$i.'">'.stripslashes(esc_attr($option)).'</option>'."\n"; } } Is there some really simple way of getting the code to output the menu say 3 times instead of once?

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• Any web services with APIs for outsourcing webapp transactional email? [closed]

  - by Tauren

  My webapp needs to send customized messages to members and I'm wondering if there is an inexpensive and easy to use web service that would meet my needs. The types of mail I will be sending include: New account activation email (sent ASAP) Daily status report of user's account (sent anytime) Event reminders (sent at specific time) Specifically, I would like the following features: RESTful API to add an email message into the send queue A way to add a priority to each message (account signup activations should be sent immediately, while a daily status report could be sent anytime each day) They manage the sending of mail and the processing of bounces Possibly, they manage opt-out/opt-in features They offer features such as DKIM, VERP, etc. If their service determines an address is undeliverable (via VERP or other means, a user unsubscribes, etc), they make a RESTful call to my web service to notify me Nice if they had some reporting features, WebBugs, link tracking, etc. What I am NOT looking for is an email marketing service that caters only to sending out copies of the same mail to masses of recipients. I need to send out unique and custom messages to individuals. I had a chat with MailChimp about using their services for sending these types of messages and they said their service does not support customized emails per recipient. Edit: I just discovered a service called JangoSMTP that appears to meet many of my requirements. It provides an API for sending mail, supports DKIM, bounce management, and even feedback loops. Unfortunately, their idea of inexpensive doesn't mesh with mine, as it would cost $180/mo to send a single daily message to my 1000 users.

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• WCF operationcontract with List type unavailable in (Silverlight) client

  - by Dave

  This is the first time I have tried returning a List of data to a Silverlight client, so I'm having trouble getting the client to recognize this operationcontract. All others are fine. I have a method on the server called ReadOwFileData that needs to return a List. ReadOwFileDataCompletedEventArgs shows up in the Object Browser in the client, but not ReadOwFileDataAsync. What I want is similar to the tutorial here. The Dictionary collection type on the client is set to System.Collections.Generic.List. I tried deleting and recreating the service reference. Web.Config on the server is using basicHttpBinding. Here is the operationcontract on the server: [OperationContract] public List<OwFileData> ReadOwFileData(string OrderID) { DataClasses1DataContext db = new DataClasses1DataContext(); var dFileData = (from p in db.OwFileDatas where p.OrderID == OrderID select p).ToList(); List<OwFileData> x = new List<OwFileData>(dFileData); return x; } Incidently, this works fine: [OperationContract] public Customer GetShippingAndContactInfo(string login, string ordernum) { DataClasses1DataContext db = new DataClasses1DataContext(); Customer dInfo = (from p in db.Customers where p.Login == login select p).Single(); return dInfo; } I would like to read this data in the client and place it into an object I created called ObservableCollection. But that obviously can't happen until the client can see the method on the server. I do not know if this is an acceptable start, but this is what is on the client so far. The ReadOwFileDataAsync object is null: void populatefilesReceivedDataSource(string OrderID) { ArtUpload.ServiceReference1.UploadServiceClient client = new ArtUpload.ServiceReference1.UploadServiceClient(); var myList = client.ReadOwFileDataAsync(OrderID); // can I just itterate thru the list instead of 'binding' }

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• servlet connection to DB

  - by underW

  Initially, after reading books on the subject, I firmly believed that the algorithm for working with a database from a servlet is as follows: create a connection - connect to the database - form a request - send the request to the database - get the query results - process them - close connection - OK. Now, with a better understanding of the practical side, I realized that nobody does it that way, and everything happens through a connection pool according to the following algorithm: initialize the servlet - create a connection pool - a request comes from a user - take a free connection from the pool - form a request - send the request to the database - get the query results - process them - return the connection back to the pool - ok. Now I have this problem: We have 100 users, they are divided into 10 groups, each group has it's own username and password to connect to the database. Moreover, each group may have different rights to the database. How am I supposed to use a connection pool in this situation? If I understand correctly, a pool is nothing more than just a group of similar connections with a single login and password. And here I have 10 pairs of username / password. It looks like I cannot use the pool in this situation. What should I do?

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• Zend Framework: How to display multiple actions, each requiring different authorizations levels, on

  - by Iain

  Imagine I have 4 database tables, and an interface that presents forms for the management of the data in each of these tables on a single webpage (using the accordion design pattern to show only one form at a time). Each form is displayed with a list of rows in the table, allowing the user to insert a new row or select a row to edit or delete. AJAX is then used to send the request to the server. A different set of forms must be displayed to different users, based on the application ACL. My question is: In terms of controllers, actions, views, and layouts, what is the best architecture for this interface? For example, so far I have a controller with add, edit and delete actions for each table. There is an indexAction for each, but it's an empty function. I've also extended Zend_Form for each table. To display the forms, I then in the IndexController pass the Forms to it's view, and echo each form. Javascript then takes care of populating the form and sending requests to the appropraite add/edit/delete action of the appropriate controller. This however doesn't allow for ACL to control the display or not of Forms to different users. Would it be better to have the indexAction instantiate the form, and then use something like $this-render(); to render each view within the view of the indexAction of the IndexController? Would ACL then prevent certain views from being rendered? Cheers.

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• C# cross thread dialogue co-operation

  - by John Attridge

  K I am looking at a primarily single thread windows forms application in 3.0. Recently my boss had a progress dialogue added on a separate thread so the user would see some activity when the main thread went away and did some heavy duty work and locked out the GUI. The above works fine unless the user switches applications or minimizes as the progress form sits top most and will not disappear with the main application. This is not so bad if there are lots of little operations as the event structure of the main form catches up with its events when it gets time so minimized and active flags can be checked and thus the dialog thread can hide or show itself accordingly. But if a long running sql operation kicks off then no events fire. I have tried intercepting the WndProc command but this also appears queued when a long running sql operation is executing. I have also tried picking up the processes, finding the current app and checking various memory values isiconic and the like inside the progress thread but until the sql operation finishes none of these get updated. Removing the topmost causes the dialog to disappear when another app activates but if the main app is then brought back it does not appear again. So I need a way to find out if the other thread is minimized or no longer active that does not involve querying the actual thread as that locks until the sql operation finishes. Now I know that this is not the best way to write this and it would be better to have all the heavy processing on separate threads leaving the GUI free but as this is a huge ancient legacy app the time to re-write in that fashion will not be provided so I have to work with what I have got. Any help is appreciated

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• Unit testing a 'legacy' WPF Application

  - by sc_ray

  The product I have been working on has been in development for the past six years. It started as a generic data entry portal into an insanely complex part WPF/part legacy application. The system has been developed for all these years without a single Unit test in its fold. Now, the point has been raised for a comprehensive unit testing framework. I have been recruited recently to work on this product and have been tasked to get the 'Testing' in order. Since the team that worked on the product for the last six years adopted 'Agile', the project lacks any documentation of the business rules or any design documents. I have been trying to write unit tests for some of the modules. But I am not sure what to Mock, how to setup my Test fixture and eventually what to Test for, since a casual glance of the methods does not reveal its intentions. Also, it has come to my attention that the code was not developed with a particular methodology in mind. Given the situation, I was wondering if the good people of Stackoverflow could provide me with some advise on how to salvage this situation. I have heard about the book 'Working with Legacy Code' that has something to say about this general situation but I was thinking about getting some pointers from individuals who have encountered similar situations within the technology stack(C#,VB,C++,.NET 3.5,WCF,SQL Server 2005).

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• Interesting Scala typing solution, doesn't work in 2.7.7?

  - by djc

  I'm trying to build some image algebra code that can work with images (basically a linear pixel buffer + dimensions) that have different types for the pixel. To get this to work, I've defined a parametrized Pixel trait with a few methods that should be able to get used with any Pixel subclass. (For now, I'm only interested in operations that work on the same Pixel type.) Here it is: trait Pixel[T <: Pixel[T]] { def mul(v: Double): T def max(v: T): T def div(v: Double): T def div(v: T): T } Now I define a single Pixel type that has storage based on three doubles (basically RGB 0.0-1.0), I've called it TripleDoublePixel: class TripleDoublePixel(v: Array[Double]) extends Pixel[TripleDoublePixel] { var data: Array[Double] = v def this() = this(Array(0.0, 0.0, 0.0)) def toString(): String = { "(" + data(0) + ", " + data(1) + ", " + data(2) + ")" } def increment(v: TripleDoublePixel) { data(0) += v.data(0) data(1) += v.data(1) data(2) += v.data(2) } def mul(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x * v)) } def div(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x / v)) } def div(v: TripleDoublePixel): TripleDoublePixel = { var tmp = new Array[Double](3) tmp(0) = data(0) / v.data(0) tmp(1) = data(1) / v.data(1) tmp(2) = data(2) / v.data(2) new TripleDoublePixel(tmp) } def max(v: TripleDoublePixel): TripleDoublePixel = { val lv = data(0) * data(0) + data(1) * data(1) + data(2) * data(2) val vv = v.data(0) * v.data(0) + v.data(1) * v.data(1) + v.data(2) * v.data(2) if (lv > vv) (this) else v } } Now I want to write code to use this, that doesn't have to know what type the pixels are. For example: def idiv[T](a: Image[T], b: Image[T]) { for (i <- 0 until a.data.size) { a.data(i) = a.data(i).div(b.data(i)) } } Unfortunately, this doesn't compile: (fragment of lindet-gen.scala):145: error: value div is not a member of T a.data(i) = a.data(i).div(b.data(i)) I was told in #scala that this worked for someone else, but that was on 2.8. I've tried to get 2.8-rc1 going, but it doesn't compile for me. Is there any way to get this to work in 2.7.7?

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• What CSS do I need to make my site more responsive?

  - by user2938757

  My site is: http://library.skybundle.com I feel like I almost have a responsive site. I did all the CSS styling myself. It is a Wordpress site but I completely edited the CSS of the original theme, so it is night-and-day different than it used to be. The original theme was mostly just for a canvas for me to work with, since I am not an expert in PHP and we wanted a Wordpress site for easy editing later on. Thanks to stackoverflow, I now have a footer that sticks to the bottom of every page and everything mostly looks good -- the way we want it anyway. The only thing missing now is the we want browser windows on MOBILE devices, such as on an iPhone, to automatically adjust the layout of the content in the body (wrapper). For example, on the main page (library.skybundle.com), I would like those two big icons two become vertically aligned as soon as the browser window sizes to a small, mostly vertical size, like that of a mobile phone. Take this site, for example: http://freedomsoundproductions.securesb.net/ This is what we would like it to do. So one a page with a sidebar, the content to the right of the sidebar should basically jump into the same "column" as the left sidebar and form one single long column. Just like in the example site above. This should all be possible via CSS. People in other forums seem to want me to use jQuery and stuff, but I can only use CSS, and I know that this must be possible without having to resort to jQuery, HTML, or other code.

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• Creating Thread in Win32

  - by Dave18

  Does ThreadFunc() gets called two times here? sometimes I notice a single call and sometimes none at all. #include <windows.h> #include <stdio.h> DWORD WINAPI ThreadFunc(LPVOID); int main() { HANDLE hThread; DWORD threadld; hThread = CreateThread(NULL, 0, ThreadFunc, 0, 0, &threadld ); printf("Thread is running\n"); } DWORD WINAPI ThreadFunc(LPVOID p) { printf("In ThreadFunc\n"); return 0; } Output 1 Thread is running In ThreadFunc In ThreadFunc Press any key to continue . . . Output 2 Thread is running In ThreadFunc Press any key to continue . . . Output 3 Thread is running Press any key to continue . . .

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• How can I write a function template for all types with a particular type trait?

  - by TC

  Consider the following example: struct Scanner { template <typename T> T get(); }; template <> string Scanner::get() { return string("string"); } template <> int Scanner::get() { return 10; } int main() { Scanner scanner; string s = scanner.get<string>(); int i = scanner.get<int>(); } The Scanner class is used to extract tokens from some source. The above code works fine, but fails when I try to get other integral types like a char or an unsigned int. The code to read these types is exactly the same as the code to read an int. I could just duplicate the code for all other integral types I'd like to read, but I'd rather define one function template for all integral types. I've tried the following: struct Scanner { template <typename T> typename enable_if<boost::is_integral<T>, T>::type get(); }; Which works like a charm, but I am unsure how to get Scanner::get<string>() to function again. So, how can I write code so that I can do scanner.get<string>() and scanner.get<any integral type>() and have a single definition to read all integral types? Update: bonus question: What if I want to accept more than one range of classes based on some traits? For example: how should I approach this problem if I want to have three get functions that accept (i) integral types (ii) floating point types (iii) strings, respectively.

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• CSS - Positioning images next to text

  - by jpjoki

  Hi, I'm doing a site in which images need to presented next to textual content - a sort of pseudo two-column layout, as the images and text come from a single html source. I've found quite a simple way to do this by putting the images as their own paragraphs and floating them. Would there still be a more simpler way (in regards to html) to do this without these extra paragraphs and by only attributing extra css to images? If the floated image is in the same paragraph than the text, then paragraphs with and without images would be different in width. EDIT: Basically, I'm looking for as simple HTML markup as possible to position images like this. The CSS can be complex ;) CSS: p { width: 500px; } p.image { float: right; width: 900px; } Current HTML: <p class="image"><img src="image.jpg" /></p> <p>Some text here.</p> Is the above possible with this HTML? <p><img src="image.jpg" /></p>

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• (How) Can I approximate a "dynamic" index (key extractor) for Boost MultiIndex?

  - by Sarah

  I have a MultiIndex container of boost::shared_ptrs to members of class Host. These members contain private arrays bool infections[NUM_SEROTYPES] revealing Hosts' infection statuses with respect to each of 1,...,NUM_SEROTYPES serotypes. I want to be able to determine at any time in the simulation the number of people infected with a given serotype, but I'm not sure how: Ideally, Boost MultiIndex would allow me to sort, for example, by Host::isInfected( int s ), where s is the serotype of interest. From what I understand, MultiIndex key extractors aren't allowed to take arguments. An alternative would be to define an index for each serotype, but I don't see how to write the MultiIndex container typedef ... in such an extensible way. I will be changing the number of serotypes between simulations. (Do experienced programmers think this should be possible? I'll attempt it if so.) There are 2^(NUM_SEROTYPES) possible infection statuses. For small numbers of serotypes, I could use a single index based on this number (or a binary string) and come up with some mapping from this key to actual infection status. Counting is still darn slow. I could maintain a separate structure counting the total numbers of infecteds with each serotype. The synchrony is a bit of a pain, but the memory is fine. I would prefer a slicker option, since I would like to do further sorts on other host attributes (e.g., after counting the number infected with serotype s, count the number of those infected who are also in a particular household and have a particular age). Thanks in advance.

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• Obtain reference to View in ActionScript class within ViewNavigatorApplication

  - by chb

  I've got a very simple project in FlashBuilder 4.5. It's a mobile application of type ViewNavigatorApplication with a single view, MapView. In the MapView.mxml file, I've got a Flex component of type Map declared in xml. <?xml version="1.0" encoding="utf-8"?> <s:View xmlns:fx="http://ns.adobe.com/mxml/2009" name="CatBusMapView"> <fx:Script> <![CDATA[ import com.esri.ags.Map; .... ]]> </fx:Script> <fx:Declarations> .... </fx:Declarations> <esri:Map id="cbm"> ... </esri:Map> </s:View> In this same project, I've an actionscript class called UserGeolocation. In this class, I'm attempting to get a reference to this map component. So far, I can get a reference to the top-level application, its ViewNavigator and the NavigationStack of said ViewNavigator. However, I cannot find a way to access the MapView, much less the map I've declared within it. I'm aware of methods like firstView() and activeView(), but I want an absolute solution, one that retrieves the view regardless of whether or not it's first or active. I've tried navigator.getChildByName("MapView") with no luck.

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• LINQ to SQL Queries odd Materialization

  - by ptoinson

  I ran across an interesting Linq to SQL, uh, feature, the other day. Perhaps someone can give me a logical explanation for the reasoning behind the results. Take the code below as my example which utilizes the AdventureWorks database setup in a Linq to SQL DataContext. This is a clip from my unit test. The resulting customer returned from a call to both CustomerQuery_Test_01() and CustomerQuery_Test_02() is the same. However, the query executed on the SQLServer are different is a major way. The method CustomerQuery_Test_01 us causing the entire Customer table to be materialized, which the call to CustomerQuery_Test_02 is only causing the single customer to be materialized. The resulting SQL Queries are at the bottom of this post. Anyone have a good reason for this? To me, it was highly non-intuitive. protected virtual Customer GetByPrimaryKey(Func<Customer, bool> keySelection) { AdventureWorksDataContext context = new AdventureWorksDataContext(); return (from r in context.Customers select r).SingleOrDefault(keySelection); } [TestMethod] public void CustomerQuery_Test_01() { Customer customer = GetByPrimaryKey(c => c.CustomerID == 2); } [TestMethod] public void CustomerQuery_Test_02() { AdventureWorksDataContext context = new AdventureWorksDataContext(); Customer customer = (from r in context.Customers select r).SingleOrDefault(c => c.CustomerID == 2); } Query for CustomerQuery_Test_01 (notice the lack of a where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] Query for CustomerQuery_Test_02 (notice the where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] WHERE [t0].[CustomerID] = @p0

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• Filtering two arrays to avoid Inf/NaN values

  - by Gacek

  I have two arrays of doubles of the same size, containg X and Y values for some plots. I need to create some kind of protection against Inf/NaN values. I need to find all that pairs of values (X, Y) for which both, X and Y are not Inf nor NaN If I have one array, I can do it using lambdas: var filteredValues = someValues.Where(d=> !(double.IsNaN(d) || double.IsInfinity(d))).ToList(); Now, for two arrays I use following loop: List<double> filteredX=new List<double>(); List<double> filteredX=new List<double>(); for(int i=0;i<XValues.Count;i++) { if(!double.IsNan(XValues[i]) && !double.IsInfinity(XValues[i]) && !double.IsNan(YValues[i]) && !double.IsInfinity(YValues[i]) ) { filteredX.Add(XValues[i]); filteredY.Add(YValues[i]); } } Is there any way of filtering two arrays at the same time using LINQ/Lambdas, as it was done for single array?

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• Core Data Errors vs Exceptions Part 3

  - by John Gallagher

  My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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• Best (functional?) programming language to learn coming from Mathematica

  - by Will Robertson

  As a mechanical engineering PhD student, I haven't had a great pedigree in programming as part of my “day job”. I started out in Matlab (having written some Hypercard and Applescript back in the day, and being introduced to Ada, of all things, in my 1st undergrad year), learned to program—if you can call it that—in (La)TeX; and finally discovered and fell for Mathematica. Now I'm interested in learning a "real" programming language that I can enjoy in the same sort of style as Mathematica, which tries to stress functional programming since it seems to map more nicely to how certain kinds of mathematics can be written algorithmically. So which functional language should I learn? I guess the obvious answer is “as many as possible”, but let's start out humble and give a single, well-considered option a good crack. I've heard good things about, say, Haskell and Scala, but I wonder if (given my non–computer science background) I'd be better off starting in more “grounded” territory and going with Ruby or Python (the latter having the big advantage of being used for Sage, which I'd also like to investigate…after my PhD). Well, I guess this is pretty subjective, so perhaps I could rephrase: would it be better to start looking at Haskell (say) straight after an ad-hoc education to functional programming in Mathematica, or will I get more out of learning Python (say) first? In reference to the question "what do I want to do with it?", I guess my answer is "fun, and learning more". I've got this list of languages that I'd like to look at, and I don't know how to trim them down. And I'd rather start with something a little higher-level than C simply so that I can be somewhat productive without having to re-invent many wheels for any code I'd like to write.

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• Using Threads to Handle Sockets

  - by user340468

  I am working on a java program that is essentially a chat room. This is an assignment for class so no code please, I am just having some issues determining the most feasible way to handle what I need to do. I have a server program already setup for a single client using threads to get the data input stream and a thread to handle sending on the data output stream. What I need to do now is create a new thread for each incoming request. My thought is to create a linked list to contain either the client sockets, or possibly the thread. Where I am stumbling is figuring out how to handle sending the messages out to all the clients. If I have a thread for each incoming message how can I then turn around and send that out to each client socket. I'm thinking that if I had a linkedlist of the clientsockets I could then traverse the list and send it out to each one, but then I would have to create a dataoutputstream each time. Could I create a linkedlist of dataoutputstreams? Sorry if it sounds like I'm rambling but I don't want to just start coding this, it could get messy without a good plan. Thanks!

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• Dimensions of a collection, and how to traverse it in an efficient, elegant manner

  - by Bruce Ferguson

  I'm trying to find an elegant way to deal with multi-dimensional collections in Scala. My understanding is that I can have up to a 5 dimensional collection using tabulate, such as in the case of the following 2-Dimensional array: val test = Array.tabulate[Double](row,col)(_+_) and that I can access the elements of the array using for(i<-0 until row) { for(j<-0 until col) { test(i)(j) = 0.0 } } If I don't know a priori what I'm going to be handling, what might be a succinct way of determining the structure of the collection, and spanning it, without doing something like: case(Array(x)) => for(i<-1 until dim1) { test(i) = 0.0 } case(Array(x,y)) => for(i<-1 until dim1) { for(j<-1 until dim2) { test(i)(j) = 0.0 } } case(Array(x,y,z)) => ... The dimensional values n1, n2, n3, etc... are private, right? Also, would one use the same trick of unwrapping a 2-D array into a 1-D vector when dealing with n-Dimensional objects if I want a single case to handle the traversal? Thanks in advance Bruce

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• LINQ - Splitting up a string with maximum length, but not chopping words apart.

  - by Stacey

  I have a simple LINQ Extension Method... public static IEnumerable<string> SplitOnLength(this string input, int length) { int index = 0; while (index < input.Length) { if (index + length < input.Length) yield return input.Substring(index, length); else yield return input.Substring(index); index += length; } } This takes a string, and it chops it up into a collection of strings that do not exceed the given length. This works well - however I'd like to go further. It chops words in half. I don't need it to understand anything complicated, I just want it to be able to chop a string off 'early' if cutting it at the length would be cutting in the middle of text (basically anything that isn't whitespace). However I suck at LINQ, so I was wondering if anyone had an idea on how to go about this. I know what I am trying to do, but I'm not sure how to approach it. So let's say I have the following text. This is a sample block of text that I would pass through the string splitter. I call this method SplitOnLength(6) I would get the following. This i s a sa mple b lock o f text that I would pass t hrough the s tring splitt er. I would rather it be smart enough to stop and look more like .. This is a sample // bad example, since the single word exceeds maximum length, but the length would be larger numbers in real scenarios, closer to 200. Can anyone help me?

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• What do you call a generalized (non-GUI-related) "Model-View-Controller" architecture?

  - by dcuccia

  I am currently refactoring code that coordinates multiple hardware components for data acquisition, and feeling a bit like I'm recreating the wheel. In particular, an MVC-like pattern seems to be emerging. Except, this has nothing to do with a GUI and I'm worried that I'm forcing this particular pattern where another might be more appropriate. Here's my scenario: Individual hardware "component" classes obey interface contracts for each hardware type. Previously, component instances were orchestrated by a single monolithic InstrumentController class, which relied heavily on configuration + branching logic for executing a specific acquisition sequence. After an iteration, I have a separate controller for each component, with these controllers all managed by a small InstrumentControllerBase (or its derivatives). The composite system will receive "input" either programmatically or via inter-hardware component triggering - in either case these interactions are routed to, and handled by, the appropriate controller. So, I have something that feels MVC-esque, but I don't know if that's because I'm forcing the point. With little direct MVC experience in application development, it's hard to know if I'm just trying to make my scenario fit MVC, where another pattern might be a good alternative or complimentary. My problem is, search results and wiki documentation of these family of patterns seems to immediately drop me into GUI-specific discussions. I understand "M means Model data and the V means View" - but do you call the superset pattern? Component-Commander-Controller? Whence can I exhume examples exemplary?

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