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• How to know if a MySQL UPDATE query fails because information being supplied matches data already in

  - by Mike

  I have a query where the user types a block of text in a textarea field. They are able to save this information in a database. The problem is that if they have not changed the information or if the information matches the data already in the database, I recieve a '0' for affected rows. Usually I display an error that says the query failed when there are no affected rows. How would I 'know' that the 0 affected rows is because the data already exists, so that I can display a more specific error?

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• Haskell Weird Kinds

  - by SHiNKiROU

  When I was experimenting with Haskell kinds, and trying to get the kind of ->, and this showed up: $ ghci ... Prelude> :k (->) (->) :: ?? -> ? -> * Prelude> Instead of the expected * -> * -> *. What are the ?? and ? things? Do they mean concrete types or "kind variables"? Or something else?

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• Accessing object's method within string

  - by Wild One

  Recently I was reading php documentation and found interesting note in string section: Functions, method calls, static class variables, and class constants inside {$} work since PHP 5. However, the value accessed will be interpreted as the name of a variable in the scope in which the string is defined. Using single curly braces ({}) will not work for accessing the return values of functions or methods or the values of class constants or static class variables. See www.php.net/manual/en/language.types.string.php It says, that I can't use curly syntax to get value returned by object's method call. Is it a mistake in manual or I misunderstood it, because I tried the following code and it works just fine: <?php class HelloWorld { public static function hello() { echo 'hello'; } } $a = new HelloWorld(); echo "{$a->hello()} world";

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• In a C++ template, is it allowed to return an object with specific type parameters?

  - by nieldw

  When I've got a template with certain type parameters, is it allowed for a function to return an object of this same template, but with different types? In other words, is the following allowed? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { /* Construct new Graph with apropriate decorators */ Graph<edgeDecor,int,dir> span = new Graph<edgeDecor,int,dir>(); /* ... */ return span; }; If this is not allowed, how can I accomplish the same kind of thing?

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• Changing a Widget's name based on a string read in from an XML form in Qt.

  - by Nick

  I'm writing a code for a voting machine that will allow user to read in custom XML ballots and then vote on them, however in the current build I have in QtCreator, I don't see an easy way to edit buttons in my GUI directly. In the code snippet below, I assign an element to pull out the names and type of ballot being read in, but I need to append a label on the GUI as well as change buttons to the names of candidates read in. Any ideas on how to do this? while(!n.isNull()){ QDomNode x = n.firstChildElement(); QDomElement e = n.toElement(); QMessageBox::information(0, tr( "Loading Element" ), tr( "Our element is %1" ).arg(e.tagName()) ); QDomElement p = x.firstChildElement();//p finds Races QMessageBox::information(0,tr("Foo"),tr("p = %1").arg(p.text()));//finds Race and Ballot types n = n.nextSibling(); } }

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• NSString inheritance

  - by Stef

  Hi, I'm doing an useless thing for my first step in Obj-C @interface String : NSString { int m_isnull; } - (id) init; - (int) isNull; @end @implementation String - (id) init { self = [super init]; m_isnull=1; return self; } - (int) isNull { return m_isnull; } @end test : String *a; a=@"ok"; Works fine, but just 2 little questions 1) When I'm compiling I have this warning warning: incompatible Objective-C types assigning 'struct NSString *', expected 'struct String *' I don't know how to avoid it !? 2) a=@"ok" is a fastest way to initialize a string, but when I'm debugging, I don't stop by at my init constructor why ?

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• extending Bash tab completion: how to handle paths / partial commands?

  - by Rawing

  I've added tab completion for my program to bash. It works quite well, but I don't know how to handle partial completion of words. Example: the user types ./program /home/user/De and presses TAB. This is then completed to ./program /home/user/Desktop/ , but there's now a trailing whitespace after 'Desktop/', which is not what I want. Basically, I need a way of preventing bash from adding whitespace after the completed word. I don't want to use bash's completion for paths.

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• Permutations with extra restrictions

  - by Full Decent

  I have a set of items, for example: {1,1,1,2,2,3,3,3}, and a restricting set of sets, for example {{3},{1,2},{1,2,3},{1,2,3},{1,2,3},{1,2,3},{2,3},{2,3}. I am looking for permutations of items, but the first element must be 3, and the second must be 1 or 2, etc. One such permutation that fits is: {3,1,1,1,2,2,3} Is there an algorithm to count all permutations for this problem in general? Is there a name for this type of problem? For illustration, I know how to solve this problem for certain types of "restricting sets". Set of items: {1,1,2,2,3}, Restrictions {{1,2},{1,2,3},{1,2,3},{1,2},{1,2}}. This is equal to 2!/(2-1)!/1! * 4!/2!/2!. Effectively permuting the 3 first, since it is the most restrictive and then permuting the remaining items where there is room.

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• Any tools can randomly generate the source code according to a language grammar?

  - by wbsun

  A C program source code can be parsed according to the C grammar(described in CFG) and eventually turned into many ASTs. I am considering if such tool exists: it can do the reverse thing by firstly randomly generating many ASTs, which include tokens that don't have the concrete string values, just the types of the tokens, according to the CFG, then generating the concrete tokens according to the tokens' definitions in the regular expression. I can imagine the first step looks like an iterative non-terminals replacement, which is randomly and can be limited by certain number of iteration times. The second step is just generating randomly strings according to regular expressions. Is there any tool that can do this?

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• Lucene boost: I need to make it work better

  - by zvikico

  I'm using Lucene to index components with names and types. Some components are more important, thus, get a bigger boost. However, I cannot get my boost to work properly. I sill get some components appear later (get worse score), even though they have a higher boost. Note that the indexing is done on one field only and I've set the boost to that field alone. I'm using Lucene in Java. I don't think it has anything to do with the field length. I've seen components with the same name (but different type) get the wrong score.

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• Qt almost same main menu entries

  - by user1671710

  I'm using c++ Qt library and I want to do something which would do : connect(actionB11, SIGNAL(triggered()), this, SLOT(SetSomething(1, 1))); connect(actionB12, SIGNAL(triggered()), this, SLOT(SetSomething(1, 2))); connect(actionB21, SIGNAL(triggered()), this, SLOT(SetSomething(2, 1))); connect(actionB22, SIGNAL(triggered()), this, SLOT(SetSomething(2, 2))); The code above doesnt work because SIGNAL function has to have same number and argument types as SLOT function. Does exist a way how to do it? I dont want to have about 20 function as SetSomething11, SetSomething12 calling SetSomething(1, 1) etc.

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• Criteria: search for two different entity classes...

  - by RoCMe

  Hi! I have a "super entity" SuperEntity and three entities ChildEntity1, ..., ChildEntity3 which extends the super class. It's easy to search for all entities in the database, i.e. we could use session.createCriteria(SuperEntity.class); It's no problem to search for one specific entity type, too, just replace the SuperEntity with any of the children to look for entities of that type. But I have a problem when allowing 'multiple choice' for the types. I.e., it could be neccessary to search all entities of type 1 and 2, but not of type 3. A first idea was to create two independent queries and join the results in a final list - but that would destroy the paging which uses offset and limit functionality of the database... Is there a possibility in Criteria to join two different queries in one single result list? Kind regards, RoCMe

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• Do c++ templates make programs slow ?

  - by user293398

  Hi, I have heard from many people that usage of templates make the code slow. Is it really true. I'm currently building a library. There are places where if templates are not created, it would result in code management problem. As of now I can think two solutions to this problem: o use #defines o Use templates and define all possible types in the header file/library itself but do not allow end user to make template instances. e.g. typedef Graph GraphI32; etc. Is there anyway, to restrict user from creating various template instances on their own. Help on above queries would be highly regarded.

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• ExpressJS: What is the difference between app.local and res.local?

  - by aeyang

  I'm trying to learn Express and in my app I have middleware that passes the session object from the Request object to my Response object so that I can access it in my views: app.use((req, res, next) -> res.locals.session = req.session next() ) But app.locals is available to the view as well right? So is it the same if I do app.locals.session = req.session? Is there a convention for the types of things app.locals and res.locals are used for? I was also confused on what the difference is between res.render() and res.redirect()? When should each be used? Thanks for reading. Any help related to Express is appreciated!

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• HandsOnTable - using date functions with methods

  - by briansol

  I have a function used on the datepicker to limit dates selected to the first of the month... I invoke it by setting a class and listener, such as: $( ".datepickfom" ).datepicker( { beforeShowDay: fom, showOn: "both", buttonImage: "/images/calendar.png", buttonImageOnly: true, changeMonth: true, changeYear: true, dateFormat: "m/d/yy", yearRange: "-25:+100", constrainInput: true } ); the fom call: function fom(date){ if (date.getDate() != 1) { return [false, "", "Specify 1st of Month"]; } return [true, ""]; } This works great for regular forms. I'm looking to extend this functionality to the HandsOnTable 'date' cell data types. var $container_1 = $("#datatable_1"); var handsontable_1 = $container_1.data('handsontable'); $("#datatable_1").handsontable( { columns: [ {}, {}, { type: 'date', dateFormat: 'm/d/yy' }, {}, { type: 'dropdown', source: ["","Y","N"] }, {}, {} ] }); This also works as it should, but the date lets me pick other dates besides the first. Is there a way to attach the beforeShowDay option to the HOT cell call as well?

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• C++: String and unions

  - by sub

  I'm having a (design) problem: I'm building an interpreter and I need some storage for variables. There are basically two types of content a variable here can have: string or int. I'm using a simple class for the variables, all variables are then stored in a vector. However, as a variable can hold a number or a string, I don't want C++ to allocate both and consume memory for no reason. That's why I wanted to use unions: union { string StringValue; int IntValue; } However, strings don't work with unions. Is there any workaround so no memory gets eaten for no reason?

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• Users and roles in context

  - by Eric W.

  I'm trying to get a sense of how to implement the user/role relationships for an application I'm writing. The persistence layer is Google App Engine's datastore, which places some interesting (but generally beneficial) constraints on what can be done. Any thoughts are appreciated. It might be helpful to keep things very concrete. I would like there to be organizations, users, test content and test administrations (records of tests that have been taken). A user can have the role of participant (test-taker), contributor of test material or both. A user can also be a member of zero or more organizations. In the role of participant, the user can see the previous administrations of tests he or she has taken. The user can also see a test administration of another participant if that participant has given the user authorization. The user can see test material that has been made public, and he or she can see restricted content as a participant during a specific administration of a test for which that user has been authorized by an organization. As a member of an organization, the user can see restricted content in the role of contributor, and he or she might or might not also be able to edit the content. Each organization should have one or more administrators that can determine whether a member can see and edit content and determine who has admin privileges. There should also be one or more application-wide superusers that can troubleshoot and solve problems. Members of organizations can see the administrations of tests that the participants concerned have authorized them to see, and they can see anonymous data if no authorization has been given. A user cannot see the test results of another user in any other circumstances. Since there are no joins in the App Engine datastore, it might be necessary to have things less normalized than usual for the typical SQL database in order to ensure that queries that check permissions are fast (e.g., ones that determine whether a link is to be displayed). My questions are: How do I move forward on this? Should I spend a lot of time up front in order to get the model right, or can I iterate several times and gradually roll in additional complexity? Does anyone have some general ideas about how to break things up in this instance? Are there any GAE libraries that handle roles in a way that is compatible with this arrangement?

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• Stringly typed values table in sql, is there a better way to do this? (we're using MSSQL)

  - by Jason Hernandez

  We have have a table layout with property names in one table, and values in a second table, and items in a third. (Yes, we're re-implementing tables in SQL.) We join all three to get a value of a property for a specific item. Unfortunately the values can have multiple data types double, varchar, bit, etc. Currently the consensus is to stringly type all the values and store the type name in the column next to the value. tblValues DataTypeName nvarchar Is there a better, cleaner way to do this?

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• Parameter pack aware std::is_base_of()

  - by T. Carter

  Is there a possibility to have a static assertion whether a type provided as template argument implements all of the types listed in the parameter pack ie. a parameter pack aware std::is_base_of()? template <typename Type, typename... Requirements> class CommonBase { static_assert(is_base_of<Requirements..., Type>::value, "Invalid."); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ parameter pack aware version of std::is_base_of() public: template <typename T> T* as() { static_assert(std::is_base_of<Requirements..., T>::value, "Invalid."); return reinterpret_cast<T*>(this); } };

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• can constructors actually return Strings?

  - by elwynn

  Hi all, I have a class called ArionFileExtractor in a .java file of the same name. public class ArionFileExtractor { public String ArionFileExtractor (String fName, String startText, String endText) { String afExtract = ""; // Extract string from fName into afExtract in code I won't show here return afExtract; } However, when I try to invoke ArionFileExtractor in another .java file, as follows: String afe = ArionFileExtractor("gibberish.txt", "foo", "/foo"); NetBeans informs me that there are incompatible types and that java.lang.String is required. But I coded ArionFileExtractor to return the standard string type, which is java.lang.string. I am wondering, can my ArionFileExtractor constructor legally return a String? I very much appreciate any tips or pointers on what I'm doing wrong here.

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• How to play an mp3 using fancybox

  - by user2980783

  I am adding fancybox to my page and to display different types of formats. I was able to implement video, text, and images seamlessly but when it doesn't load the audio. Once I click on the audio file on the gallery it opens on a blank page. I am trying to play the track as iframe if possible. Can anyone help with this. Thank you. <a class="hover-wrap" data-fancybox-type="iframe" data-fancybox-group="music" title="Breathin'" href="_include/download/Breathin'.mp3"> <span class="overlay-img"></span> <span class="overlay-img-thumb font-icon-plus"></span> <p class="description"> <span class="title">Song</span> </p> </a>

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• RESTful enums. string or Id?

  - by GazTheDestroyer

  I have a RESTful service that exposes enums. Should I expose them as localised strings, or plain integers? My leaning is toward integers for easy conversion at the service end, but in that case the client needs to grab a list of localised strings from somewhere in order to know what the enums mean. Am I just creating extra steps for nothing? There seems to be little information I can find about which is commonly done in RESTful APIs. EDIT: OK. Let's say I'm writing a website that stores information about people's pets. I could have an AnimalType enum 0 Dog 1 Cat 2 Rabbit etc. When people grab a particular pet resource, say /pets/1, I can either provide a meaningful localised string for the animal type, or just provide the ID and force them to do another look up via a /pets/types resource. Or should I provide both?

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• Java application return codes

  - by doele

  I have a Java program that processes one file at a time. This Java program is called from a wrapper script which logs the return code from the Java program. There are 2 types of errors. Expected errors and unexpected errors. In both cases I just need to log them. My wrapper knows about 3 different states. 0-OK, 1-PROCESSING_FAILED, 2- ERROR. Is this a valid approach? Here is my approach: enum ReturnCodes {OK,PROCESSING_FAILED,ERROR}; public static void main(String[] args) { ... proc.processMyFile(); ... System.exit(ReturnCodes.OK.ordinal()); } catch (Throwable t) { ... System.exit(ReturnCodes.ERROR.ordinal()); } private void processMyFile() { try { ... }catch( ExpectedException e) { ... System.exit(ReturnCodes.PROCESSING_FAILED.ordinal()); } }

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• Function Composition in Haskell

  - by Watts

  I have a function that takes 3 functions and switches the types and combine to make a new function. For example a test case call would be : (chain init tail reverse ) "Haskell!" the output should be lleksa I've tried to do this problem a few different ways including using the map function but I kept getting association problems. so i did chain :: Ord a => [a] -> a chain f g h x = f.g.h$x my error is Couldn't match expected type[t0->t1->t2->a0] When I type the problem directly into prelude like replacing f, g, h, x with the values it comes out right Is there even a way to do three functions, I've only seen two in examples

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• Converting byte[] of binary fixed point to floating point value?

  - by Sean Donohue

  I'm reading some data over a socket. The integral data types are no trouble, the System.BitConverter methods are correctly handling the conversion. (So there are no Endian issues to worry about, I think?) However, BitConverter.ToDouble isn't working for the floating point parts of the data...the source specification is a bit low level for me, but talks about a binary fixed point representation with a positive byte offset in the more significant direction and negative byte offset in the less significant direction. Most of the research I've done has been aimed at C++ or a full fixed-point library handling sines and cosines, which sounds like overkill for this problem. Could someone please help me with a C# function to produce a float from 8 bytes of a byte array with, say, a -3 byte offset?

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