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  • What is the best signature for overloaded arithmetic operators in C++?

    - by JohnMcG
    I had assumed that the canonical form for operator+, assuming the existence of an overloaded operator+= member function, was like this: const T operator+(const T& lhs, const T& rhs) { return T(lhs) +=rhs; } But it was pointed out to me that this would also work: const T operator+ (T lhs, const T& rhs) { return lhs+=rhs; } In essence, this form transfers creation of the temporary from the body of the implementation to the function call. It seems a little awkward to have different types for the two parameters, but is there anything wrong with the second form? Is there a reason to prefer one over the other?

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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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  • 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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  • referencing struct fields in c with square brackets and an index instead of . and ->?

    - by lsiebert
    Assuming I have a structure such as: typedef struct { char * string1; char * string2; } TWO_WORDS; such that all the fields are of the same type, and my main has TWO_WORDS tw; can I reference string1 with tw[0] and string2 with two[1]? If so: is this part of the c standard? do i have to cast the struct to an array first? what about fields which are different sizes in memory what about fields which are different types but the same size? can you do pointer arithmetic within a structure? -

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  • Is using a DataSet's column Expression works in background same as manual calculation?

    - by Harikrishna
    I have one datatable which is not bindided and records are coming from the file by parsing it in the datatable dynamically every time. Now there is three columns in the datatable Marks1,Marks2 and FinalMarks. And their types is decimal. Now for making addition of columns Marks1 and Marks2 's records and store it into FinalMarks column,For that what I do is : datatableResult.Columns["FinalMarks"].Expression="Marks1+Marks2"; It's works properly. It can be done in other way also is foreach (DataRow r in datatableResult.Rows) { r["FinalMarks"]=Convert.ToDecimal(r["Marks1"])+Convert.ToDecimal(r["Marks2"]); } Is first approach same as second approach in background means is both approach same or what? EDIT: I want to know that first approach works in background as second approach.

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  • How do I print the method body reflectively?

    - by kunjaan
    Right now I have private static void getMethods(Class<? extends Object> clazz) { Method[] declaredMethods = clazz.getDeclaredMethods(); for (Method aMethod : declaredMethods) { aMethod.setAccessible(true); // Print the declaration System.out.print(Modifier.toString(aMethod.getModifiers()) + " " + aMethod.getReturnType().getSimpleName() + " " + aMethod.getName()); // Get Parameter Types getParameters(aMethod); //Empty Body System.out.println("{}\n"); } } Which prints most information reflectively but creates an empty body. How do I add to the reflective nature of Java to print the method body?

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  • regex no character

    - by iamnotmad
    In this text: warning here there are several types of warnings in this string warning.gif at the end warning end of line warning I want to match every warning except warning.gif. I cannot seem to get it to include the last one that has no character (control or otherwise) after it. using warnings?[^\.] gets what I want except for the last warning (on the last line). I think because there is no character at all after. How can I get it to include that one?

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  • Assigning a pointer variable to a const int in C++?

    - by John
    I'm wondering if anyone can explain the following to me: If I write int i = 0; float* pf = i; I get a compile error (gcc 4.2.1): error: invalid conversion from ‘int’ to ‘float*’ Makes sense - they are obviously two completely different types. But if instead I write const int i = 0; float* pf = i; It compiles without error. Why should the 'const' make a difference on the right hand side of the assignment? Isn't part of the idea of the 'const' keyword to be able to enforce type constraints for constant values? Any explanation I have been able to come up with feels kind of bogus. And none of my explanations also explain the fact that const int i = 1; float* pf = i; fails to compile. Can anyone offer an explanation?

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  • How do I get a Type[] with arguments from a MethodCallExpression?

    - by Tomas Lycken
    I'm reflecting over a class (in a unit test of said class) to make sure its members have all the required attributes. To do so, I've constructed a couple of helpers, that take an Expression as an argument. I do some checks for it, and take slightly different actions depending on what type of Expression it is, but it's basically the same. Now, my problem is that I have several methods with the same name (but different signatures), and the following code throws an AmbiguousMatchException: // TOnType is a type argument for the type where the method is declared // mce is the MethodCallExpression var m = typeof(TOnType).GetMethod(mce.Method.Name); Now, if I could add an array of Type[] with the types of the arguments to this method as a second parameter to .GetMethod(), the problem would be solved. But how do I find this Type[] array that I need? I have cast the Expression<Func<...>> to an Expression, and then to a MethodCallExpression, and in this method the contents of <...> is not known.

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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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  • Core Data: Detecting the type and casting it

    - by Tim Sullivan
    I have set up a Core Data model that includes an entity, Item with a 1-M relationship with the abstract entity Place, so that an item has many places. There are several entities with the parent set to Place. I want to set up several UI elements depending on the descendent place types. I have a loop that looks something like this: for (Place *place in item.places) { } ... but I'm not sure how to detect what type the place is, and how to cast it to the proper type so that I can access its properties. Thanks for any help!

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  • Creating Slugs from Titles?

    - by James Jeffery
    I have everything in place to create slugs from titles, but there is one issue. My RegEx replaces spaces with hyphens. But when a user types "Hi     there" (multiple spaces) the slug ends up as "Hi-----there". When really it should be "Hi-there". Should I create the regular expression so that it only replaces a space when there is a character either side? Or is there an easier way to do this?

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  • Any way to not break on certain errors in Visual Studio 2010?

    - by Vulgrin
    I'm working on a VS2010 project where I'm using DataAnnotations on my objects to handle validation. However, this is sort of a pain in the butt while trying to do interactive debugging because it keeps pausing VS.Net on validation errors. Obviously, I want to break on some errors, but not these particular types. Am I out of luck and I just need to turn on and off my Break on All Errors setting? Or is there some way to tell VS to just ignore these when they happen? (these are errors generated via Validator.ValidateProperty calls.) Thanks

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  • Drupal: tag multiselection.. but not anymore possible adding new tags

    - by Patrick
    hi, I've installed Taxonomy SuperSelect module in my Drupal. Now my customer can not only type the tag for some content types pages but also select multiple tags using checkboxes. I've also ordered the chekboxes alphabetically. However few days ago, I noticed that he can't anymore manually type the tags.. see picture: http://dl.dropbox.com/u/72686/multiSelect.png Can you help me how to solve this issue ? What's the php template to edit this pages ? Unluckily I don't remember if I edited some code, since I found out after a while this bug. thanks

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  • Can a method return an NSRange?

    - by Dan Donaldson
    I have a method that returns an NSRange. When I call this method from outside the class I get a compile error. NSRange tmpRange; tmpRange = [phrase rangeInString:searchString forString:theLetter goingForward:YES]; return tmpRange.location == -1; in the .h file: #import <Foundation/Foundation.h> @interface Phrase : NSObject { } - (NSRange) rangeInString:(NSString *) tgt forString:(NSString *) find goingForward:(BOOL) fwd; @end This method is called within the Phrase object by other methods without problems. The compiler says 'incompatible types in assignment'. Can anyone explain this to me? I assume it has to do with returning an NSRange/struct type value generated outside the object, but I don't know why it works in one place and not the other.

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  • How to coerce type of ActiveRecord attribute returned by :select phrase on joined table?

    - by tribalvibes
    Having trouble with AR 2.3.5, e.g.: users = User.all( :select => "u.id, c.user_id", :from => "users u, connections c", :conditions => ... ) Returns, e.g.: => [#<User id: 1000>] >> users.first.attributes => {"id"=>1000, "user_id"=>"1000"} Note that AR returns the id of the model searched as numeric but the selected user_id of the joined model as a String, although both are int(11) in the database schema. How could I better form this type of query to select columns of tables backing multiple models and retrieving their natural type rather than String ? Seems like AR is punting on this somewhere. How could I coerce the returned types at AR load time and not have to tack .to_i (etc.) onto every post-hoc access?

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  • Calling inheriting class methods via interface.

    - by Stacey
    Given the scenario... interface IBase{ void Process(int value); } abstract class Base : IBase { public virtual void Process(int value){ throw new NotImplementedException(); } } class Implemented: Base, IBase { public void Process(int value) { // .. some code here.. } } I'm trying to write a loop similar to the following. foreach( Base b in CollectionOfImplemented ) { b.Process( // something will go here // ); } Trying this, it keeps calling Base.Process, instead of Implemented.Process; but the type in the collection is Implemented, not Base. Boxing it seems to work, but I was hoping to see if I could find a more intelligent approach to it, since the Collection will contain other types of objects that also inherit from Base.

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  • Optimal way to initialize varying objects

    - by John Smith
    I have to initialize a lot of different types of objects based on an integer parameter. They all have the same overall initialization methods. At the moment I have the following code #def APPLE 1 #def PEAR 2 switch (t) { case APPLE: newobj = [[FApple alloc] init]; break; case PEAR: newobj = [[FPear] alloc] init]; break; default: retobj = nil; } I believe there must be a better way to do this. When I add FOrange I have to go and add another line here. What would be a better way?

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  • Best way to save info in hash

    - by qwertymk
    I have a webpage that the user inputs data into a textarea and then process and display it with some javascript. For example if the user types: _Hello_ *World* it would do something like: <underline>Hello</underline> <b>World</b> Or something like that, the details aren't important. Now the user can "save" the page to make it something like site.com/page#_Hello_%20*World* and share that link with others. My question is: Is this the best way to do this? Is there a limit on a url that I should be worried about? Should I do something like what jsfiddle does? I would prefer not to as the site would work offline if the full text would be in the hash, and as the nature of the site is to be used offline, the user would have to first cache the jsfiddle-like hash before they could use it. What's the best way to do this?

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  • Where is the 'indeterminate type'?

    - by Daniel
    I'm defining the following type extension: type System.Reflection.MemberInfo with member x.GetAttribute<'T when 'T :> Attribute>(required, inherit') = match required, Attribute.GetCustomAttribute(x, typeof<'T>, inherit') with | true, null -> invalidOp (sprintf "Missing required attribute: %s" typeof<'T>.FullName) | _, attr -> attr :> 'T The last match expression (attr :> 'T) gives the error: The static coercion from Attribute to 'T involves an indeterminate type based on information prior to this program point. Static coercions are not allowed on some types. Further type annotations are needed. I've tried annotating the function return type, but got the same result. I would hate to change this to a dynamic cast. Is there a way to make the static cast work?

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  • Searching Arrays, array_search() issue

    - by Mikey1980
    Is there any way I can search an array for a value and return it's key, I tried array_search() with no success... below is an example of my array [0] = Array ( [value] = [text] = All Call Types ) [1] => Array ( [value] => enquiry [text] => Renovation Enquiry ) [2] => Array ( [value] => msg [text] => Message to Pass on ) ... My ultimate goal is to convert value to text. Here's what I tried: $key = array_search($row['call_type'], $type_list); $call_type_name = $type_list[$key]['text']; Thanks!

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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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  • Switch Case on type of object (C#)

    - by Sem Dendoncker
    If you want to switch a type of object, what is the best way to do this? ex: private int GetNodeType(NodeDTO node) { switch (node.GetType()) { case typeof(CasusNodeDTO): return 1; case typeof(BucketNodeDTO): return 3; case typeof(BranchNodeDTO): return 0; case typeof(LeafNodeDTO): return 2; default: return -1; } } I know this doesn't work that way, but I was wondering how you could solve this. Is an if then else else else statement appropriate in this case? Or do you use this switch and add .ToString() to the types? Kind regards, Sem

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  • Case Sensitivity of Action Names in Struts 2

    - by IK
    Is there an easy way to make Struts 2 action names case insensitive? Currently I have the following action defined: <action name="printTest" class="MyClass" > <result name="error">/WEB-INF/jsp/error.jsp</result> <result name="input">/WEB-INF/jsp/test.jsp</result> <result name="success">/WEB-INF/jsp/test.jsp</result> </action> If the user types URL "/app/printtest.do" instead of "/app/printtest.do" this action is not executed. Other then mod_rewrite on the httpd level or something like that, the only option that I know about right now is simply adding the same exact action and changing the name to "printtest". Ideally it would be a simple config change to struts.xml

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  • Putting logic in ViewModel get'ers

    - by Yngvebn
    What do you think about putting Get-logic in the getters of a ViewModel? Something like: public class DummyViewModel { public int Id { get; set; } private DummyObject myObject; public DummyObject MyObject { get { if (MyObject == null) { DummyRepository repo = new DummyRepository(); myObject = repo.Get(Id); } return myObject; } } } Is this bad practice, or totally fine? I find my controllers getting really bloated by doing all the get-logic there, but I'm really torn as to where I should put it... My reason for doing it this way, is that I can pass the ViewModel to different types of view, and only the neccessary DB-lookup will be performed based on what property is requested.

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