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• java: libraries for immutable functional-style data structures

  - by Jason S

  This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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• Extremely CPU Intensive Alarm Clock

  - by SoulBeaver

  For some reason my program, a console alarm clock I made for laughs and practice, is extremely CPU intensive. It consumes about 2mB RAM, which is already quite a bit for such a small program, but it devastates my CPU with over 50% resources at times. Most of the time my program is doing nothing except counting down the seconds, so I guess this part of my program is the one that's causing so much strain on my CPU, though I don't know why. If it is so, could you please recommend a way of making it less, or perhaps a library to use instead if the problem can't be easily solved? /* The wait function waits exactly one second before returning to the * * called function. */ void wait( const int &seconds ) { clock_t endwait; // Type needed to compare with clock() endwait = clock() + ( seconds * CLOCKS_PER_SEC ); while( clock() < endwait ) {} // Nothing need be done here. } In case anybody browses CPlusPlus.com, this is a genuine copy/paste of the clock() function they have written as an example for clock(). Much why the comment //Nothing need be done here is so lackluster. I'm not entirely sure what exactly clock() does yet. The rest of the program calls two other functions that only activate every sixty seconds, otherwise returning to the caller and counting down another second, so I don't think that's too CPU intensive- though I wouldn't know, this is my first attempt at optimizing code. The first function is a console clear using system("cls") which, I know, is really, really slow and not a good idea. I will be changing that post-haste, but, since it only activates every 60 seconds and there is a noticeable lag-spike, I know this isn't the problem most of the time. The second function re-writes the content of the screen with the updated remaining time also only every sixty seconds. I will edit in the function that calls wait, clearScreen and display if it's clear that this function is not the problem. I already tried to reference most variables so they are not copied, as well as avoid endl as I heard that it's a little slow compared to \n.

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• How To Update EF 4 Entity In ASP.NET MVC 3?

  - by Jason Evans

  Hi there. I have 2 projects - a class library containing an EDM Entity Framework model and a seperate ASP.NET MVC project. I'm having problems with how your suppose to edit and save changes to an entity using MVC. In my controller I have: public class UserController : Controller { public ActionResult Edit(int id) { var rep = new UserRepository(); var user = rep.GetById(id); return View(user); } [HttpPost] public ActionResult Edit(User user) { var rep = new UserRepository(); rep.Update(user); return View(user); } } My UserRepository has an Update method like this: public void Update(User user) { using (var context = new PDS_FMPEntities()) { context.Users.Attach(testUser); context.ObjectStateManager.ChangeObjectState(testUser, EntityState.Modified); context.SaveChanges(); } } Now, when I click 'Save' on the edit user page, the parameter user only contains two values populated: Id, and FirstName. I take it that is due to the fact that I'm only displaying those two properties in the view. My question is this, if I'm updating the user's firstname, and then want to save it, what am I suppose to do about the other User properties which were not shown on the view, since they now contain 0 or NULL values in the user object? I've been reading a lot about using stub entities, but I'm getting nowhere fast, in that none of the examples I've seen actually work. i.e. I keep getting EntityKey related exceptions. Can someone point me to a good tutorial/example of how to update EF 4 entities using a repository class, called by an MVC front-end? Cheers. Jas.

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• Retrieve the Value of An Integer Variable

  - by Abluescarab

  This is probably easily figured out (I feel very stupid right now), but I can't find a solution anywhere, for some reason. Perhaps I'm not searching for the right thing. And maybe it's in some beginner tutorial I haven't watched. Anyway, I was wondering how to retrieve the value of an integer variable in C++? I know you can use cin.getline() for string variables, but I received an error message when I attempted that with an integer variable (and rightfully so, I know it was wrong, but I was looking for a solution). My project is a Win32 console application. What I'm trying to do is ask a user to input a number, stored in the variable n. Then I take the value of n and perform various math functions with it. In my header file, I have string, windows, iostream, stdio, math, and fstream. Do I need to add another library? There's not much more to tell. I can post my code if I must. EDIT: cout << "TEST SINE"; cout << "\nPlease enter a number.\n\n"; cin >> n; break; Here's the code I'm trying to use. Is this all I need to do? If so, how do I incorporate the variable so I can test it using sin, cos, and tan? Yet again, thanks ahead of time.

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• Rewriting jQuery to plain old javascript - are the performance gains worth it?

  - by Swader

  Since jQuery is an incredibly easy and banal library, I've developed a rather complex project fairly quickly with it. The entire interface is jQuery based, and memory is cleaned regularly to maintain optimum performance. Everything works very well in Firefox, and exceptionally so in Chrome (other browsers are of no concern for me as this is not a commercial or publicly available product). What I'm wondering now is - since pure plain old javascript is really not a complicated language to master, would it be performance enhancing to rewrite the whole thing in plain old JS, and if so, how much of a boost would you expect to get from it? If the answers prove positive enough, I'll go ahead and do it, run a benchmark and report back with the precise findings. Cheers Edit: Thanks guys, valuable insight. The purpose was not to "re-invent the wheel" - it was just for experience and personal improvement. Just because something exists, doesn't mean you shouldn't explore it into greater detail, know how it works or try to recreate it. This is the same reason I seldom use frameworks, I would much rather use my own code and iron it out and gain massive experience doing it, than start off by using someone else's code, regardless of how ironed out it is. Anyway, won't be doing it, thanks for saving me the effort :)

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• libcurl (c api) READFUNCTION for http PUT blocking forever

  - by Duane

  I am using libcurl for a RESTful library. I am having two problems with a PUT message, I am just trying to send a small content like "hello" via put. My READFUNCTION for PUT's blocks for a very large amount of time (minutes) when I follow the manual at curl.haxx.se and return a 0 indicating I have finished the content. (on os X) When I return something 0 this succeeds much faster (< 1 sec) When I run this on my linux machine (ubuntu 10.4) this blocking event appears to NEVER return when I return 0, if I change the behavior to return the size written libcurl appends all the data in the http body sending way more data and it fails with a "too much data" message from the server. my readfunction is below, any help would be greatly appreciated. I am using libcurl 7.20.1 typedef struct{ void *data; int body_size; int bytes_remaining; int bytes_written; } postdata; size_t readfunc(void *ptr, size_t size, size_t nmemb, void *stream) { if(stream) { postdata ud = (postdata)stream; if(ud->bytes_remaining) { if(ud->body_size > size*nmemb) { memcpy(ptr, ud->data+ud->bytes_written, size*nmemb); ud->bytes_written+=size+nmemb; ud->bytes_remaining = ud->body_size-size*nmemb; return size*nmemb; } else { memcpy(ptr, ud->data+ud->bytes_written, ud->bytes_remaining); ud->bytes_remaining=0; return 0; } }

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• Efficient way to maintain a sorted list of access counts in Python

  - by David

  Let's say I have a list of objects. (All together now: "I have a list of objects.") In the web application I'm writing, each time a request comes in, I pick out up to one of these objects according to unspecified criteria and use it to handle the request. Basically like this: def handle_request(req): for h in handlers: if h.handles(req): return h return None Assuming the order of the objects in the list is unimportant, I can cut down on unnecessary iterations by keeping the list sorted such that the most frequently used (or perhaps most recently used) objects are at the front. I know this isn't something to be concerned about - it'll make only a miniscule, undetectable difference in the app's execution time - but debugging the rest of the code is driving me crazy and I need a distraction :) so I'm asking out of curiosity: what is the most efficient way to maintain the list in sorted order, descending, by the number of times each handler is chosen? The obvious solution is to make handlers a list of (count, handler) pairs, and each time a handler is chosen, increment the count and resort the list. def handle_request(req): for h in handlers[:]: if h[1].handles(req): h[0] += 1 handlers.sort(reverse=True) return h[1] return None But since there's only ever going to be at most one element out of order, and I know which one it is, it seems like some sort of optimization should be possible. Is there something in the standard library, perhaps, that is especially well-suited to this task? Or some other data structure? (Even if it's not implemented in Python) Or should/could I be doing something completely different?

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• Which compiler option I should choose?

  - by Surjya Narayana Padhi

  Hi Geeks, I have to use the third party static library for my qt application to run on windows. The third party provides me a .lib and .h file for use. These libraries are compiled with MSVC compiler. My qt Creator is using MinGW compiler to compile my application. I copied the .h and .lib file to my qt project directory and then added those in .pro file as follows QT += core gui TARGET = MyTest TEMPLATE = app LIBS += C:\Qt\2010.05\qt\MyTest\newApi.lib SOURCES += main.cpp\ mainwindow.cpp HEADERS += mainwindow.h \ newApi.h FORMS += mainwindow.ui Now I am getting some runtime error like this - Starting C:\Qt\2010.05\qt\MyTest-build-desktop\debug\MyTest.exe... C:\Qt\2010.05\qt\MyTest-build-desktop\debug\MyTest.exe exited with code -1073741515 Can any body suggest is this runtime error is due to mismatch of compiler? (because of my .lib file I added is comipled in MSVC compiler and my qt app is compiled using MinGW compiler) If not what may be the reason? Am I missing anything in adding the .h and .lib file to my qt project? If my MinGW compiler will not support the .lib file generated in MSVC compiler what may be the work-arround? Can I create the .lib files in MinGW compiler? or this format is supported only by MSVC compiler only? Please suggest...

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• reading newlines with FORMAT statement

  - by peter.murray.rust

  I'm writing a preprocessor and postprocessor for Fortran input and output using FORMAT-like statements (there are reasons not to use a FORTRAN library). I want to treat the new line ("/") character correctly. I don't have a Fortran compiler immediately to hand. Is there a simple algorithm for working out how many newlines are written or consumed (This post just gives reading examples) [Please assume a FORTRAN77-like mentality in the FORTRAN code and correct any FORTRAN syntax on my part] UPDATE: no comments yet so I am reduced to finding a compiler and running it myself. I'll post the answers if I'm not beaten to it. No-one commented I had the format syntax wrong. I've changed it but there may still be errors Assume datafile 1 a b c d etc... (a) does the READ command always consume a newline? does READ(1, '(A)') A READ(1, '(A)') B give A='a' and B='b' (b) what does READ(1,'(A,/)') A READ(1,'(A)') B give for B? (I would assume 'c') (c) what does READ(1, '(/)') READ(1, '(A)') A give for A (is it 'b' or 'c') (d) what does READ(1,'(A,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'b' and 'c') (e) what does READ(1,'(A,/,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'c' and 'd')? Are there any cases in which the '/' is redundant?

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• Why does PEAR get installed to my user directory?

  - by webworm

  I am new to Linux and I am attempting to install the PHP PEAR library on a virtual server which is running Ubuntu. I am following a tutorial that covers installing PEAR but have run up against an area where I am confused. When running the PEAR installation program I am prompted as to what I want the INSTALL_PREFIX to be. Evidently the INSTALL_PREFIX, among other things, determines where PEAR will be installed. The tutorial suggest the value of INSTALL_PREFIX be the following path ... "/home/MY_USER_NAME/pear" where MY_USER_NAME = my user account Having come from a Windows world, applications are installed on the system where everyone can use them. If I install PEAR underneath my user directory will other developers on the system be able to make use of PEAR in their PHP scripts? I want to make PEAR available to all users and not just myself. Could someone explain to me the difference between installing for all users and installing just for myself? Does the install location matter? Should I be installing PEAR in a different location? Thanks for any suggestions. P.S. The tutorial I am following is located at the following URL ... http://articles.sitepoint.com/article/getting-started-with-pear/2

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• How does one gets started with Winforms style applications on Win32?

  - by Billy ONeal

  EDIT: I'm extremely tired and frustrated at the moment -- please ignore that bit in this question -- I'll edit it in the morning to be better. Okay -- a bit of background: I'm a C++ programmer mostly, but the only GUI stuff I've ever done was on top of .NET's WinForms platform. I'm completely new to Windows GUI programming, and despite Petzold's excellent book, I'm extremely confused. Namely, it seems that most every reference on getting started with Win32 is all about drawing lines and curves and things -- a topic about which (at least at present time) I couldn't care less. I need a checked list box, a splitter, and a textbox -- something that would take less than 10 minutes to do in Winforms land. It has been recommended to me to use the WTL library, which provides an implementation of all three of these controls -- but I keep getting hung up on simple things, such as getting the damn controls to use the right font, and getting High DPI working correctly. I've spent two freaking days on this, and I can't help but think there has to be a better reference for these kinds of things than I've been able to find. Petzold's book is good, but it hasn't been updated since Windows 95 days, and there's been a LOT changed w.r.t. how applications should be correctly developed since it was published. I guess what I'm looking for is a modern Petzold book. Where can I find such a resource, if any?

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• problem in handling menu - submenu based on spring security

  - by Nirmal

  Hi All... I have configured spring security core plugin using requestmap table inside the database.. Now inside requestmap table I have all the possible urls and it's equivalent roles who can access that url... Now I want to generate menus and submenus based on the urls stored in requestmap table... So my requirement is to check the urls of menu & submenus against the logged in users privileges... And if logged in user has any one privilege then I need to display that main menu and the available submenus.... For e.g. I have a menu in my project called user which has a following submenus : **Users (main menu)** Manage Users (sub menu) Import Users (sub menu) Now inside my header.gsp I have successfully achieved the above requirement using if else condition, like : if ( privs.contains("/users/manageUsers") || privs.contains("/users/importUsers")) here privs are the list of urls from requestmap table for logged in user. But I want to achieve these using spring security tag lib, so for comparing urls I have find following tag from spring security core documentation : <sec:access url="/users/manageUsers"> But i am bit confuse that how I can replace or condition using tag library.. Is there any tag available which checks from multiple urls and evaluate it to true or false ? Of course I can do using sec:access tag with some flag logic, but is there any tags available which can fulfill my requirement directly ? Thanks in advance...

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• Glassfish 3: How do I get and use a developers build so I can navigate a stack trace including Glas

  - by Thorbjørn Ravn Andersen

  I am migrating a JSF 1.1 application to JEE 6 Web profile, and doing it in steps. I am in the process of moving from JSP with JSF 1.1 to Facelets under JSF 1.2 using the jsf-facelets.jar for JSF 1.2, and received an "interesting" stack trace when trying to lookup a key in a Map using a "{Bean.foo.map.key}" where the stacktrace complained about "key" not being a valid integer. (After code introspection I am workarounding it using a number as the key). That bug is not what this question is about. In such a situation it is essential to be able to navigate the source of every line in the stack trace. In Eclipse I normally attach a source jar to every jar on the build path, but in this particular case the Glassfish server adapter creates a library automatically containing the jars. Also there is to my knowledge no debug build of Glassfish where sources are included in the bundle. Glassfish is a non-trivial Maven project, and a bit picky too. I am not very familiar with maven, but have managed to checkout the code from Subversion and build it for the 3.0 tag according to http://wiki.glassfish.java.net/Wiki.jsp?page=V3FullBuildInstructions#section-V3FullBuildInstructions-CheckoutTheWorkspace - it appears to be the code corresponding to the official released 3.0 version. After finishing the "mvn -U install" part, I have then tried to create Eclipse projects by first using "mvn -DdownloadSources=true eclipse:eclipse" and then import them in Eclipse JEE 3.5.2 and specifying the M2_REPO variable but many of the projects still have compilation errors, and I cannot locate any instructions from Oracle about how to do this. I'd appreciate some help in just getting a functional IDE workspace reflecting the 3.0 version of Glassfish. I have Eclipse 3.5.2, Netbeans 6.8 and 6.9 beta, and IntelliJ IDEA 9, and Linux/Windows/OS X do do it on.

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• I don't like Python functions that take two or more iterables. Is it a good idea?

  - by Xavier Ho

  This question came from looking at this question on Stackoverflow. def fringe8((px, py), (x1, y1, x2, y2)): Personally, it's been one of my pet peeves to see a function that takes two arguments with fixed-number iterables (like a tuple) or two or more dictionaries (Like in the Shotgun API). It's just hard to use, because of all the verbosity and double-bracketed enclosures. Wouldn't this be better: >>> class Point(object): ... def __init__(self, x, y): ... self.x = x ... self.y = y ... >>> class Rect(object): ... def __init__(self, x1, y1, x2, y2): ... self.x1 = x1 ... self.y1 = y1 ... self.x2 = x2 ... self.y2 = y2 ... >>> def fringe8(point, rect): ... # ... ... >>> >>> point = Point(2, 2) >>> rect = Rect(1, 1, 3, 3) >>> >>> fringe8(point, rect) Is there a situation where taking two or more iterable arguments is justified? Obviously the standard itertools Python library needs that, but I can't see it being pretty in maintainable, flexible code design.

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• PDFParsing & extracting the images only in iPhone application.

  - by sagar

  Hello - Every one. ** : My Query : ** I want to extract only images from entire pdf document. ( Using Objective C - for iPhone Application ) : My Efforts : I have gone through this link which has details regarding different operators of PDF Document. ( http://mail-archives.apache.org/mod_mbox/pdfbox-commits/200912.mbox/%[email protected]%3E ) I also studied this document - ( http://developer.apple.com/mac/library/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_pdf_scan/dq_pdf_scan.html#//apple_ref/doc/uid/TP30001066-CH220-TPXREF101 ) I also have gone through entire document of PDFReference.pdf ( From original Adobe Site ) PDFReference.pdf (Adobe Document - says that - for image there are following operators ) q Q BI EI I have placed following table get the image myTable = CGPDFOperatorTableCreate(); CGPDFOperatorTableSetCallback(myTable, "q", arrayCallback2); CGPDFOperatorTableSetCallback(myTable, "TJ", arrayCallback); CGPDFOperatorTableSetCallback(myTable, "Tj", stringCallback); I have following arrayCallback2 method for getting image void arrayCallback2(CGPDFScannerRef inScanner, void *userInfo) { // how to extract image from this code // means I have tried too many different ways. following is incorrect way & not giving image // CGPDFStreamRef stream; // represents a sequence of bytes // if (CGPDFDictionaryGetStream (d, "BI", &stream)){ // CGPDFDataFormat t=CGPDFDataFormatJPEG2000; // CFDataRef data = CGPDFStreamCopyData (stream, &t); // } } above arrayCallback2 method is called for operator "q", But I don't know How to extract the image from it. In short. What should be the solution for extracting the images from the pdf documents? Thanks in advance for your kind help. Sagar kothari.

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• Is it possible in Perl to require a subroutine call is made?

  - by MitchelWB

  I don't know enough about Perl to even know what I'm asking for exactly, but I'm writing a series of subroutines to be available for many individual scripts that all process different incoming flat files. The process is far from perfect, but it's what I've got to deal with and I'm trying to build myself a small library of subs that make it easier for me to manage it all. Each script handles a different incoming flat file with it's own formatting, sorting, grouping and outputting requirements. One common aspect is that we have small text files that house counters that are used to name the output files so that we have no duplicate file names. Because the processing of the data is different for each file, I need to open the file to get my counter value, because this is a common operation, I'd like to put it in a sub to retrieve the counter. But then need to write specific code to process the data. And would like a second sub that allows me to update the counter with the counter once I've processed the data. Is there a way to make the second sub call a requirement if the first one is called? Ideally if it could even be an error that would prevent the script from running at all much like a syntax error. EDIT: Here is a little [ugly and simplified] psuedo-code to give a better feel for what the current process is: require "importLibrary.plx"; #open data source file open DataIn, $filename; #call getCounterInfo from importLibrary.plx to get the counter value from counter file $counter = &getCounterInfo($counterFileName); while (<DataIn>) { #Process data based on unique formatting and requirements #output to task files based on requirements and name files using the $counter #increment $counter } #update counter file with new value of $counter &updateCounterInfo($counter);

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• Android - Where to store generated bitmaps?

  - by Josh

  I've got an app which dynamically generates anywhere from 6 to 100 small bitmaps for the user to move around the screen in a given session. I currently generate them in onCreate and store them to the sd card, so that after an orientation change I can grab them out of external storage and display them again. However, this takes time (the loading) and I'd like to keep the bitmap references around between lifecyle changes for quicker access. My question is, is there a better place to store my generated bitmaps? I was thinking about creating a static storage library in my base activity, something that would only need to be reloaded when the app is completely removed from memory (shutdown, other apps need resources, 30 minute restart, etc). Ideally, I'd like the user to be able to back out to the title screen, click a "Resume" button, and in onCreate I just have access to those resident bitmap references instead of having to load them from storage again. For this reason I don't think Activity.onRetainNonConfigurationInstance is what I need. Alternatively, is there a better way to handle multiple generated bitmaps than what I'm doing or the plan I described?

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• Call .NET Webservice with Android

  - by Lasse P

  Hi, I know this question has been asked here before, but I don't think those answers were adequate for my needs. We have a SOAP webservice that is used for an iPhone application, but it is possible that we need an Android specific version or a proxy of the service, so we have the option to go with either SOAP or JSON. I have a few concerns about both methods: SOAP solution: Is it possible to generate java source code from a WSDL file, if so, will it include some kind of proxy class to invoke the webservice and will it work in the Android environment at all? Google has not provided any SOAP library in Android, so i need to use 3rd party, any suggestion? What about the performance/overhead with parsing and transmitting SOAP xml over the wire versus the JSON solution? JSON solution: There is a few classes in the Android sdk that will let me parse JSON, but does it support generic parsing, like if I want the result to be parsed as a complex type? Or would I need to implement that myself? I have read about 2 libraries before here on Stackoverflow, GSON an Jackson. What is the difference performance and usability (from a developers perspective) wise? Do you guys have any experince with either of those libraries? So i guess the big question is, what method to go with? I hope you can help me out. Thanks in advance :-)

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• form:select items problem in spring mvc portlet

  - by dhaval

  I have a set of drop-down control which I want to render with my custom tag library. The following is the code of the tag lib: <spring:bind path="${path}"> <c:choose> <c:when test="${readOnly}"> <span class="readOnly">${status.value}</span> </c:when> <c:otherwise> <form:select path="${path }" itemLabel="${label }" itemValue="${value }" items="${itemList}"> </form:select> </c:otherwise> </c:choose> And this is the code I have written in the JSP file: <tag:conditionalListControl path="model.selectedCountry" readOnly="false" label="name" value="id" listItems="model.countryList" className="simple" /> Upon execution the paring returns the following error: [jsp:165] javax.servlet.jsp.JspException: Type [java.lang.String] is not valid for option items But if i change the items="${itemList}" to items="${model.countryList}" which is the list I want to display, it works fine without any problem and also bind to required variables on form submit. But i don't want to hard code any variables in the tag lib. Any suggestions???

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• Howto use predicates in LINQ to Entities for Entity Framework objects

  - by user274947

  I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic on in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities."} Solution in that question suggests to use AsExpandable() method from LINQKit library. But again, using public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.AsExpandable().Where(x => isMatched(x)); } I'm getting the exception Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression' Is there way to use predicate in LINQ to Entities query for Entity Framework objects, so that it is correctly transformed it into a SQL statement. Thank you.

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• Java-Hibernate: How can I translate these tables to hibernate annotations?

  - by penas

  I need to create a simple application using these tables: http://stackoverflow.com/questions/2612848/are-these-tables-respect-the-3nf-database-normalization I have created the application using simple old JDBC, but I would like to see how the application would look like using Hibernate, but I don't know how to put the sql code in java. I have found LOTS of examples, but I'm pretty much confused about using Hibernate and I don't know If I made such a good joob. For example, for the first three tables: AUTHOR table * Author_ID, PK * First_Name * Last_Name TITLES table * TITLE_ID, PK * NAME * Author_ID, FK DOMAIN table * DOMAIN_ID, PK * NAME * TITLE_ID, FK The code in java: Table 1 @Entity @Table(name = "AUTHORS", schema = "LIBRARY") public class Author{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "Author_ID") private int authorId; @Column(name = "First_Name", nullable = false, length = 50) private String firstName; @Column(name = "Last_Name", nullable = false, length = 40) private String lastName; @OneToMany @JoinColumn(name = "Title_ID") private List<Title> titles; Table 2 @Entity @Table(name = "TITLES") public class Title{ @Id @Column(name = "Title_ID") private int titleID; @Column(name = "Name", nullable = false, length = 50) private String name; @ManyToOne @JoinColumn(name = "Domain_ID") private Domain domains; Table 3 @Entity @Table(name = "DOMAINS") public class Domain{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "Domain_ID") private int Domain_ID; @Column(name = "Name", nullable = false, length = 50) private String name; @OneToOne(mappedBy = "domains") private Title title; } Any good? :)

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• How can I get a iterable resultset from the database using pdo, instead of a large array?

  - by Tchalvak

  I'm using PDO inside a database abstraction library function query. I'm using fetchAll(), which if you have a lot of results, can get memory intensive, so I want to provide an argument to toggle between a fetchAll associative array and a pdo result set that can be iterated over with foreach and requires less memory (somehow). I remember hearing about this, and I searched the PDO docs, but I couldn't find any useful way to do that. Does anyone know how to get an iterable resultset back from PDO instead of just a flat array? And am I right that using an iterable resultset will be easier on memory? I'm using Postgresql, if it matters in this case. . . . The current query function is as follows, just for clarity. /** * Running bound queries on the database. * * Use: query('select all from players limit :count', array('count'=>10)); * Or: query('select all from players limit :count', array('count'=>array(10, PDO::PARAM_INT))); **/ function query($sql_query, $bindings=array()){ DatabaseConnection::getInstance(); $statement = DatabaseConnection::$pdo->prepare($sql_query); foreach($bindings as $binding => $value){ if(is_array($value)){ $statement->bindParam($binding, $value[0], $value[1]); } else { $statement->bindValue($binding, $value); } } $statement->execute(); // TODO: Return an iterable resultset here, and allow switching between array and iterable resultset. return $statement->fetchAll(PDO::FETCH_ASSOC); }

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• App is fast on 3GS but slow on 3G

  - by Anthony Chan

  Hi all, I'm new to computer coding and have just finished coding an app and tested it on both 3G and 3GS. On 3GS, it worked as normal as on the simulator. However, when I tried to run it on 3G, the app becomes extremely slow. I'm not sure what's the reason and I hope someone could shed some light on me. Generally, my app has a couple of view controller classes, with one of them being the title page, one being the main page, one is setting, etc. I used a dissolve to transition from the title page to the main page. But even this simple transition shows un-smooth performance on a 3G! My other part of the app involves zooming in to some images by scaling up the images, switching images by push or dissolve upon receiving touch events, saving photos into photo library and storing and retrieving some photos in a folder and some data in a SQlite database, each showing un-smooth actions. Compared with some heavy graphic or heavy maths app, I think mine is pretty simple. I totally have no clue why the app would behave so slow and un-smooth that it is barely useful on a 3G. Any help/ direction would be much appreciated. Thanks for helping out.

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• jQuery Manual Resizable DIV

  - by JC

  Hi, I'm trying to create a resizable div without using jQuery's interface library. var myY = 0; var mouseDown = false; var originalHeight = 0; function resize(e){ if(mouseDown == true){ $("#cooldiv").height(originalHeight+e.pageY-myY); } } $(document).ready(function(){ $().mouseup(function(e){ myY = 0; mouseDown = false; originalHeight = 0; $().unbind("mousemove", resize); }); $("#resizeBar").mousedown(function(e){ myY = e.pageY; originalHeight = $("#cooldiv").height(); mouseDown = true; $().bind("mousemove", resize); }); }); ... <div id="cooldiv" style="width: 500px; height: 300px; background-color: #cccccc; position: relative;"> <div id="resizeBar" style="height: 10px; width: 500px; background-color: #aaaaaa; position: absolute; bottom: 0;"></div> </div> The first resize works fine(i.e. mousedown, mousemove then mouseup), but on subsequent (mousedown+mousemove)s, the browser attempts to drag the whole resizeBar div instead of properly resizing its parent container. On mouseup, the div then starts resizing "cooldiv" on mousemove without any mousedown required, until a further click of the mouse. These problems don't show up in Internet Explorer.

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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