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• How to parse a string (by a "new" markup) with R ?

  - by Tal Galili

  Hi all, I want to use R to do string parsing that (I think) is like a simplistic HTML parsing. For example, let's say we have the following two variables: Seq <- "GCCTCGATAGCTCAGTTGGGAGAGCGTACGACTGAAGATCGTAAGGtCACCAGTTCGATCCTGGTTCGGGGCA" Str <- ">>>>>>>..>>>>........<<<<.>>>>>.......<<<<<.....>>>>>.......<<<<<<<<<<<<." Say that I want to parse "Seq" According to "Str", by using the legend here Seq: GCCTCGATAGCTCAGTTGGGAGAGCGTACGACTGAAGATCGTAAGGtCACCAGTTCGATCCTGGTTCGGGGCA Str: >>>>>>>..>>>>........<<<<.>>>>>.......<<<<<.....>>>>>.......<<<<<<<<<<<<. | | | | | | | || | +-----+ +--------------+ +---------------+ +---------------++-----+ | Stem 1 Stem 2 Stem 3 | | | +----------------------------------------------------------------+ Stem 0 Assume that we always have 4 stems (0 to 3), but that the length of letters before and after each of them can very. The output should be something like the following list structure: list( "Stem 0 opening" = "GCCTCGA", "before Stem 1" = "TA", "Stem 1" = list(opening = "GCTC", inside = "AGTTGGGA", closing = "GAGC" ), "between Stem 1 and 2" = "G", "Stem 2" = list(opening = "TACGA", inside = "CTGAAGA", closing = "TCGTA" ), "between Stem 2 and 3" = "AGGtC", "Stem 3" = list(opening = "ACCAG", inside = "TTCGATC", closing = "CTGGT" ), "After Stem 3" = "", "Stem 0 closing" = "TCGGGGC" ) I don't have any experience with programming a parser, and would like advices as to what strategy to use when programming something like this (and any recommended R commands to use). What I was thinking of is to first get rid of the "Stem 0", then go through the inner string with a recursive function (let's call it "seperate.stem") that each time will split the string into: 1. before stem 2. opening stem 3. inside stem 4. closing stem 5. after stem Where the "after stem" will then be recursively entered into the same function ("seperate.stem") The thing is that I am not sure how to try and do this coding without using a loop. Any advices will be most welcomed.

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• ASP.NET: how can I compile in DEBUG mode?

  - by Budda

  AFAIK, usual ASP.NET web site/web application switched on into DEBUG mode when web/app-config setting "compilation" has debug="false". But I don't clearly understand how it works. Let's consider example: I have <compilation debug="true" />. I've added the following line into "Page_Load" method: System.Diagnostics.Debug.WriteLine("Page_Load"); When I launched web-site in 'debug' mode (using F5 button) It put me 'Page_Load' into output window. Everything is ok so far. When I change application compilation mode into non-debug: Will it recompile everything for 'non-debug' mode? Is this enough to go into "production" environment with this change only? I guess, it should be enough for web-site that doesn't use other project. Otherwise, I would better switch whole configuration into "Release" mode. In this case EACH project will be recompiled in "Release" mode. Am I right? Could you please point me if something is wrong here? Thanks a lot!

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• CakePHP - recursive on specific fields in model?

  - by Paul

  Hi, I'm pretty new to CakePHP but I think I'm starting to get the hang of it. I'm trying to pull related table information recursively, but I want to specify which related models to recurse on. Let me give you an example to demonstrate my goal: I have a model "Customer", which has info like Company name, website, etc. "Customer" hasMany "Addresses", which contain info for individual contacts like Contact Name, Street, City, State, Country, etc. "Customer" also belongsTo "CustomerType", which is just has descriptive category info - a name and description, like "Distributor" or "Manufacturer". When I do a find on "Customer" I want to get associated "CustomerType" and "Address" info as sub-arrays, and this works fine just by setting up the hasMany and belongsTo associations properly. But now, here's my issue: I want to get associated State/Country info. So, instead of each "Address" array row just having "state_id", I want it to have "state" = array("id" = 20, "name" = "New York",...) etc. If I set $recursive to a higher value (e.g., 2) in the Partner model, I get what I want for the State/Country info in each "Address". BUT it also recurses on "CustomerType", and that results in the "CustomerType" field of my "Partner" object having a huge array of all Customer objects that match that type, which could be thousands long. So the point is, I DON'T want to recurse on "CustomerType", only on "Address". Is there a way I can set this up? Sorry for the long-winded question, and thanks in advance!

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• static member specialization of templated child class and templated base class

  - by b3nj1

  I'm trying to have a templated class (here C) that inherits from another templated class (here A) and perform static member specialization (of int var here), but I cant get the right syntax to do so (if it's possible #include <iostream> template<typename derived> class A { public: static int var; }; //This one works fine class B :public A<B> { public: B() { std::cout << var << std::endl; } }; template<> int A<B>::var = 9; //This one doesn't works template<typename type> class C :public A<C<type> > { public: C() { std::cout << var << std::endl; } }; //template<> template<typename type> int A<C<type> >::a = 10; int main() { B b; C<int> c; return 0; } I put an example that works with a non templated class (here B) and i can get the static member specialization of var, but for C that just doesn't work. Here is what gcc tells me : test.cpp: In constructor ‘C<type>::C()’: test.cpp:29:26: error: ‘var’ was not declared in this scope test.cpp: At global scope: test.cpp:34:18: error: template definition of non-template ‘int A<C<type> >::a’ I'm using gcc version 4.6.3, thanks for any help

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• Insertion sort invariant assertion fails

  - by user1661211

  In the following code at the end of the for loop I use the assert function in order to test that a[i+1] is greater than or equal to a[i] but I get the following error (after the code below). Also in c++ the assert with the following seems to work just fine but in python (the following code) it does not seem to work...anyone know why? import random class Sorting: #Precondition: An array a with values. #Postcondition: Array a[1...n] is sorted. def insertion_sort(self,a): #First loop invariant: Array a[1...i] is sorted. for j in range(1,len(a)): key = a[j] i = j-1 #Second loop invariant: a[i] is the greatest value from a[i...j-1] while i >= 0 and a[i] > key: a[i+1] = a[i] i = i-1 a[i+1] = key assert a[i+1] >= a[i] return a def random_array(self,size): b = [] for i in range(0,size): b.append(random.randint(0,1000)) return b sort = Sorting() print sort.insertion_sort(sort.random_array(10)) The Error: Traceback (most recent call last): File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 27, in <module> print sort.insertion_sort(sort.random_array(10)) File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 16, in insertion_sort assert a[i+1] >= a[i] AssertionError

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• Recursion - Ship Battle

  - by rgorrosini

  I'm trying to write a little ship battle game in java. It is 100% academic, I made it to practice recursion, so... I want to use it instead of iteration, even if it's simpler and more efficient in most some cases. Let's get down to business. These are the rules: Ships are 1, 2 or 3 cells wide and are placed horizontally only. Water is represented with 0, non-hit ship cells are 1, hit ship cells are 2 and sunken ships have all it's cells in 3. With those rules set, I'm using the following array for testing: int[][] board = new int[][] { {0, 1, 2, 0, 1, 0}, {0, 0, 1, 1, 1, 0}, {0, 3, 0, 0, 0, 0}, {0, 0, 2, 1, 2, 0}, {0, 0, 0, 1, 1, 1}, }; It works pretty good so far, and to make it more user-friendly I would like to add a couple of reports. these are the methods I need for them: Given the matrix, return the amount of ships in it. Same as a), but separating them by state (amount of non-hit ships, hit and sunken ones). I will need a hand with those reports, and I would like to get some ideas. Remember it must be done using recursion, I want to understand this, and the only way to go is practice! Thanks a lot for your time and patience :).

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• is there a Java GUI for dummies ?

  - by MHero

  Hello, first I want to apologize about my english, it may be not clear enough. Well, I'm new to Java programming, and I search over this web about use of Swing, AWT, 2D, etc. but I didn't get the answer I was looking for. I want to know about a book or method to learn Java GUI programming (not even sure this is a propper term). Previous answers guide me to Filthy Rich Clients by Romain Guy and also to The Swing Tutorial in Sun Web Page. and No offense, but...the first one seems too complex and the second one a bit disorganize. so I ask about a more "for dummies" method. Thanks EDIT: Thanks everyboy, you're very kind and serious. I want to clear some things that I didn't state for being my first question. I dont' want to use autogenerated code(Don't want to say why only focus on my question for consistency) Also I've read Deitel & Deitel and it's a good beginners book but it seems to me that doesn't cover layout(and other details) Finally, I tried to read netbeans generated code but it's a mess find method by method and function by function the way that the IDE does it I hope this edition helps to solve my question

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• Use of Java [Interfaces / Abstract classes]

  - by Samuel

  Hello, Lately i decided to take a look at Java so i am still pretty new to it and also to the approach of OO programming, so i wanted to get some things straight before learning more, (i guess it's never to soon to start with good practices). I am programming a little 2D game for now but i think my question applies to any non trivial project. For the simplicity i'll provide examples from my game. I have different kinds of zombies, but they all have the same attributes (x, y, health, attack etc) so i wrote an interface Zombie which i implement by WalkingZombie, RunningZombie TeleportingZombie etc. Is this the best thing to do? Am i better of with an abstract class? Or with a super class? (I am not planning to partially implement functions - therefor my choice for an interface instead of an abstract class) I have one class describing the main character (Survivor) and since it is pretty big i wanted to write an interface with the different functions, so that i can easily see and share the structure of it. Is it good practice? Or is it simply a waste of space and time? I hope this question will not be rated as subjective because i thought that experienced programmers won't disagree about this kind of topic since the use of interfaces / super classes / abstract classes follows logical rules and is thereby not simply a personal choice. Thank you for your time -Samuel

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• Querying using table-valued parameter

  - by antmx

  I need help please with writing a sproc, it takes a table-valued parameter @Locations, whose Type is defined as follows: CREATE TYPE [dbo].[tvpLocation] AS TABLE( [CountryId] [int] NULL, [ResortName] [nvarchar](100) NULL, [Ordinal] [int] NOT NULL, PRIMARY KEY CLUSTERED ( [Ordinal] ASC )WITH (IGNORE_DUP_KEY = OFF) ) @Locations will contain at least 1 row. Each row WILL have a non-null CountryId, and MAY have a non-null ResortName. Each row will have a unique Ordinal, the first being 0. The combinations of CountryId and ResortName in @Locations will be unique. The sproc needs to search against the following table structure. The image can be seen better by right-clicking it and View Image, or similar depending on your browser. Now this is where I'm stuck, the sproc should be able to find Tours where: The Tour's 1st TourHotel (Ordinal 0) has the same CountryId (and ResortName if specified) of the 1st row of @Locations (Ordinal 0). And also if @Locations has 1 row, the Tour must have additional TourHotels, ALL of which must be in the remaining CountryIds (and ResortNames if specified) of these remaining @Locations rows. Edit This is the code I finally used, based on Anthony Faull's suggestion. Thank you so much Anthony: select distinct T.Id from tblTour T join tblTourHotel TH on TH.TourId = T.Id join tblHotel H ON H.Id = TH.HotelId JOIN @Locations L ON ( ( L.Ordinal = 0 AND TH.Ordinal = 0 ) OR ( L.Ordinal > 0 AND TH.Ordinal > 0 ) ) AND L.CountryId = H.CountryId AND ( L.ResortName = H.ResortName OR L.ResortName IS NULL ) cross apply( select COUNT(TH2.Id) AS [Count] FROM tblTourHotel TH2 where TH2.TourId = TH.TourId ) TourHotelCount where TourHotelCount.[Count] = @LocationCount group by T.Id, T.TourRef, T.Description, T.DepartureDate, T.NumNights, T.DepartureAirportId, T.DestinationAirportId, T.AirlineId, T.FEPrice having COUNT(distinct TH.Id) = @LocationCount

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• Coding the R-ight way - avoiding the for loop

  - by mropa

  I am going through one of my .R files and by cleaning it up a little bit I am trying to get more familiar with writing the code the r-ight way. As a beginner, one of my favorite starting points is to get rid of the for() loops and try to transform the expression into a functional programming form. So here is the scenario: I am assembling a bunch of data.frames into a list for later usage. dataList <- list (dataA, dataB, dataC, dataD, dataE ) Now I like to take a look at each data.frame's column names and substitute certain character strings. Eg I like to substitute each "foo" and "bar" with "baz". At the moment I am getting the job done with a for() loop which looks a bit awkward. colnames(dataList[[1]]) [1] "foo" "code" "lp15" "bar" "lh15" colnames(dataList[[2]]) [1] "a" "code" "lp50" "ls50" "foo" matchVec <- c("foo", "bar") for (i in seq(dataList)) { for (j in seq(matchVec)) { colnames (dataList[[i]])[grep(pattern=matchVec[j], x=colnames (dataList[[i]]))] <- c("baz") } } Since I am working here with a list I thought about the lapply function. My attempts handling the job with the lapply function all seem to look alright but only at first sight. If I write f <- function(i, xList) { gsub(pattern=c("foo"), replacement=c("baz"), x=colnames(xList[[i]])) } lapply(seq(dataList), f, xList=dataList) the last line prints out almost what I am looking for. However, if i take another look at the actual names of the data.frames in dataList: lapply (dataList, colnames) I see that no changes have been made to the initial character strings. So how can I rewrite the for() loop and transform it into a functional programming form? And how do I substitute both strings, "foo" and "bar", in an efficient way? Since the gsub() function takes as its pattern argument only a character vector of length one.

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• Which CSS identifier is used for the selected tab in tabbed tables in browsers other than IE?

  - by David Navarre

  When you have a table on a form in Notes, you can choose to display only one row at a time (via the Special Table Row Display parameter on the Table Rows tab of the Table properties). In a Notes document displayed using Internet Explorer that contains such a table, a row is displayed with a cell for each "tab". The TD that serves as the tab for the selected "Notes table row" is assigned <td class="dominoSelTopTab">, while the other tabs get <td class="dominoTopTab">. However, when using other browsers, it's not nearly as simple. In Firefox, each "tab" ends up as a single-celled-single-row-table within the table with very little to identify it. <td><table border="1" cellpadding="2"> <tr><td><div align="center"><b>Tab 2</b></div></td></tr> </table></td> A non-selected tab would show as follows: <td><table border="1" cellpadding="2"> <tr><td><div align="center"><a name="1." href="/Projects/MyCSS.nsf/0c3b9489476440c085257a62006d97d6/d482a1767a4af77f85257a62006db064?OpenDocument&amp;TableRow=1.0#1." target="_self">Tab 1</a></div></td></tr> </table></td> So, the question is, how do I identify the selected tabs and the non-selected tabs when not using IE? Note: For those who are not Notes developers, the HTML is auto-generated from the visual design as laid out in the Notes designer client. I would replace it all with manual HTML, except there is so much of it that doing so would consume far too much time.

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• C++ IDE for Linux?

  - by Sven

  I want to expand my programming horizons to Linux. A good, dependable basic toolset is important, and what is more basic than an IDE? I could find these SO topics: Lightweight IDE for linux and What tools do you use to develop C++ applications on Linux? I'm not looking for a lightweight IDE. If an IDE is worth the money, then I will pay for it, so it need not be free. My question, then: What good, C++ programming IDE is available for Linux? The minimums are fairly standard: syntax highlighting, code completion (like intellisense or its Eclipse counterpart) and integrated debugging (e.g., basic breakpoints). I have searched for it myself, but there are so many that it is almost impossible to separate the good from the bads by hand, especially for someone like me who has little C++ coding experience in Linux. I know that Eclipse supports C++, and I really like that IDE for Java, but is it any good for C++ and is there something better? The second post actually has some good suggestions, but what I am missing is what exactly makes the sugested IDE so good for the user, what are its (dis)advantages? Maybe my question should therefore be: What IDE do you propose (given your experiences), and why?

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• Why can’t I create a database in an empty ASP MVC 2 project using Project->Add->New Item->SQL Server

  - by Dr Dork

  I'm diving head first into ASP MVC and am playing around with creating and manipulating a database. I did a search and found this tutorial for creating a database, however when I follow it, I get this error right at the start when trying to add a new database to my fresh, empty ASP MVC 2 project... A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) The only requirement the tutorial mentioned was SQL Server Express, but when I went to download it, it said it was already installed. I'm assuming it was part of the VS 2010 RC I installed and am running. So I don't know what else I need if I am missing something. This is all new to me, so I'm sure I'm missing something obvious here and after I'm done posting this question, I plan to do some more research into the topic of databases and how they work with ASP MVC. In the meantime, I was you could help me answer a couple high level questions... What am I missing/forgetting to do that is causing this error? Any suggestions for good resources/tutorials that focus on using databases with ASP MVC? I've done a lot of database programming in the past, so I'm familiar with the concepts of relational databases and the SQL language. I wish I could find a good resource for learning how to work with them in an ASP dev environment, as well as a good breakdown of all the related technologies used for working with them (i.e. LINQ to SQL). Thanks so much in advance for all your help! I'm going to start researching these questions right now.

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• Problem with Java FX Look and Feel

  - by drachenfels

  Hi, I was looking at some of the examples from the Deitel and Deitel's book for Programming in Java, and one of the first examples is a very simple Swing display. Hence this snippet of code : import javax.swing.*; public class cdea { public static void main(String args[]){ JOptionPane.showMessageDialog(null,"\"Welcome to Java Programming!\""); System.exit(0); //end method main } } I read some stuff regarding how one can get native UI look and feel by using UIManager.setLookAndFeel( UIManager.getSystemLookAndFeelClassName()); to the program. However, when I just add this to my main method, it gives me a host of errors. Specifically : Multiple markers at this line - Unhandled exception type IllegalAccessException - Unhandled exception type InstantiationException - Unhandled exception type ClassNotFoundException - Unhandled exception type UnsupportedLookAndFeelException However when I use it as part of a try/catch exception loop (is that what it is called?) as detailed on http://stackoverflow.com/questions/1590863/getting-java-applications-to-look-native-on-windows-how , I get the program running properly. Could anyone tell me in simple language why this is so? As in, why can't I directly get the System look and feel; why do I have to use it with exception handling? I'm new to Java, and OOP in general, so I'm sorry if I'm being too simplistic.

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• xpath php attributes not working?

  - by Jared

  Getting this error Call to a member function attributes() on a non-object I have found multiple answers to this on SO, but none of them seem to solve my problem? Here is the XML: <Routes> <Route type="source" name="incoming"> </Route> <Routes> Here is the PHP: $doc = new SimpleXMLElement('routingConfig.xml', null, true); class traverseXML { function getData() { global $doc; $routeCount = count($doc -> xpath("Route")); //this value returns correctly $routeArr = array(); for ($i = 1; $i <= $routeCount; $i++) { $name = $doc -> Route[$i] -> attributes() -> name; array_push($routeArr, $name); } return $routeArr; } } $traverseXML = new traverseXML; var_dump($traverseXML -> getData()); I understand what the error means, but how is it a non-object? How do I return the name attribute of Routes/Route[1] ?

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• What happens when you create an instance of an object containing no state in C#?

  - by liquorice

  I am I think ok at algorithmic programming, if that is the right term? I used to play with turbo pascal and 8086 assembly language back in the 1980s as a hobby. But only very small projects and I haven't really done any programming in the 20ish years since then. So I am struggling for understanding like a drowning swimmer. So maybe this is a very niave question or I'm just making no sense at all, but say I have an object kind of like this: class Something : IDoer { void Do(ISomethingElse x) { x.DoWhatEverYouWant(42); } } And then I do var Thing1 = new Something(); var Thing2 = new Something(); Thing1.Do(blah); Thing2.Do(blah); does Thing1 = Thing2? does "new Something()" create anything? Or is it not much different different from having a static class, except I can pass it around and swap it out etc. Is the "Do" procedure in the same location in memory for both the Thing1(blah) and Thing2(blah) objects? I mean when executing it, does it mean there are two Something.Do procedures or just one?

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• UTF-8 support in java application

  - by jacekn

  I'm having trouble with UTF-8. common.jsp <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> typical.jsp <%@ include file="common.jsp" %> Page Head <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> Form <form id="screenObject" accept-charset="UTF-8" action="/SiteAdmin/articleHeaderEdit?articleId=15" method="post"> I enter non latin1 characters into a text field and click Save. Validator complains about another field and stops the submission. This never gets to the database, so database ability to handle UTF-8 is not in this picture. The page redisplays with appropriate error but the text that had been entered is all messed up. All non latin1 characters are converted to some gibberish. I'm using Spring 3 MVC, in case that matters... Attempts Adding this to my view resolver didn't help: <property name="contentType" value="text/html;charset=UTF-8" />

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• Using the JPA Criteria API, can you do a fetch join that results in only one join?

  - by Shaun

  Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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• is there a simple timed lock algorithm avoiding deadlock on multiple mutexes?

  - by Vicente Botet Escriba

  C++0x thread library or Boost.thread define a non-member variadic template function that locks all mutex at once that helps to avoid deadlock. template <class L1, class L2, class... L3> void lock(L1&, L2&, L3&...); The same can be applied to a non-member variadic template function try_lock_until, which locks all the mutex until a given time is reached that helps to avoid deadlock like lock(...). template <class Clock, class Duration, class L1, class L2, class... L3> void try_lock_until( const chrono::time_point<Clock,Duration>& abs_time, L1&, L2&, L3&...); I have an implementation that follows the same design as the Boost function boost::lock(...). But this is quite complex. As I can be missing something evident I wanted to know if: is there a simple timed lock algorithm avoiding deadlock on multiple mutexes? If no simple implementation exists, can this justify a proposal to Boost? P.S. Please avoid posting complex solutions.

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• Strange compilation error on reference passing argument to function

  - by Grewdrewgoo Goobergabbsoen

  Here's the code: #include <iostream> using namespace std; void mysize(int &size, int size2); int main() { int *p; int val; p = &val; cout << p; mysize(&val, 20); // Error is pointed here! } void mysize(int &size, int size2) { cout << sizeof(size); size2 = size2 + 6000; cout << size2; } Here's the error output from GCC: In function 'int main()': Line 10: error: invalid initialization of non-const reference of type 'int&' from a temporary of type 'int*' compilation terminated due to -Wfatal-errors. What does that imply? I do not understand the error message ... invalid initialization of a non-constant? I declared the prototype function above with two parameters to take, one a reference of an integer and one just an integer value itself. I passed the reference of the int (see line 10), yet this error keeps being thrown at me. What is the issue?

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• MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

  - by user568249

  I'm currently working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to either be real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 0 and SD 1. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do this. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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• Practice of checking 'trueness' or 'equality' of conditional statements - does it really make sense?

  - by senthilkumar1033

  I remember many years back, when I was in school, one of my computer science teachers taught us that it was better to check for 'trueness' or 'equality' of a condition and not the negative stuff like 'inequality'. Let me elaborate - If a piece of conditional code can be written by checking whether an expression is true or false, we should check the 'trueness'. Example: Finding out whether a number is odd - it can be done in two ways: if ( num % 2 != 0 ) { // Number is odd } or if ( num % 2 == 1 ) { // Number is odd } When I was beginning to code, I knew that num % 2 == 0 implies the number is even, so I just put a ! there to check if it is odd. But he was like 'Don't check NOT conditions. Have the practice of checking the 'trueness' or 'equality' of conditions whenever possible.' And he recommended that I use the second piece of code. I am not for or against either but I just wanted to know - what difference does it make? Please don't reply 'Technically the output will be the same' - we ALL know that. Is it a general programming practice or is it his own programming practice that he is preaching to others?

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• Help - use PHP-broswer, or proxy or get_page_contents or include page, or something else ??

  - by userlite

  Hi, I am trying to develop a web application for which I need to capture a specific user-driven event (such as mouse dblclick) occurring on a different-website page loaded through my website. What I want to do is : User visits my website - hosted by me. There, user types in any website URL (e.g.: http://www.example.com) That URL page gets loaded as is. When user double-clicks mouse over any link or image from that page, a popup/side-panel is displayed with content related to that particular image or link. I can do this with a combination of PHP get_page_contents or include-page, and javascript dblclick. However, when user clicks on any link or submits a form, the control goes to that other website, where I cannot show the side-panel. I might be able to handle the links by proxifying them when user clicks on any of them. How do I handle forms submission and other stuff ? I can use a full-featured proxy, but that will be too heavy just for the purpose of capturing the event. My question is that is there a way to write some kind of light PHP script that sits on my website - that loads other websites contents as is, but lets me capture the mouse-dblclick event to show related-content in the side panel . I have already searched the internet, but could not find anything. Any help is really appreciated. Thanks.

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• Binding Javascript Event Handlers to a an Ajax HTML Response?

  - by John

  Let's say I have the following HTML code <div id="outer"> <div id="inner">Hello World</div> </div> At the end of my HTML page, I use javascript to attach event handlers like so, document.getElementById('inner').onclick = function() {alert(this.innerHTML);} document.getElementById('outer').onclick = function() { /* An Ajax Call where the response, which will be a string of HTML content, then goes into document.getElementById('outer').innerHTML */ document.getElementById('inner').onclick = function() {alert(this.innerHTML);} } In the above code, I am expecting <div id="inner">Hello World 2</div> to come back which requires me to re-attach the onclick event handler. This makes sense because the new response coming back is just a string, and I have to tell the browser that after converting to DOM, i also need some event handlers So my question is, is there a better way to manage event handlers on AJAX response that contains HTML content? I could use inline javascript within the html response, but then it prevents me from achieving non-intrusive javascript. So is there a way to achieve non-intrusive javascript and an efficient way to "maintain" event handlers of ajax html responses?

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