Search Results

Search found 4503 results on 181 pages for 'logical operator'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 34/181 | < Previous Page | 30 31 32 33 34 35 36 37 38 39 40 41  | Next Page >

  • Logical volume that spans raid1 sets: what happens if a RAID fails?

    - by Jeff Shattock
    Consider the following scenario: /dev/md0 - 10GB RAID 1 volume built from /dev/sda and /dev/sdb /dev/md1 - 10GB RAID 1 volume built from /dev/sdc and /dev/sdd /dev/vg0 - volume group containing md0 and md1 /dev/vg0/lv0 - 15GB logical volume The raid devices are created with mdadm; the logical volumes by LVM. What happens to lv0 if md0 fails entirely? That is, if both sda and sdb disintegrate so that the md0 device can not start. Is the portion of the data that resided on md1 still accessible, or is the entire LV gone? Would the answer change if lv0 were created as a striped volume vs non-striped?

    Read the article

  • Does /boot safe on top of a lvm LV (logical volume)?

    - by fantoman
    Title already asked the question. More specifically, I read in some documents that logical volumes are nice in general but not for /boot in a linux system. They say that bootloaders don't understand LVM volumes, so create a separate partition for /boot out of lvm. I recently installed Ubuntu server (9.10) for my home server, but by default /boot is created in the LVM. Everything is fine now, but I am not sure it is safe to use /boot in LVM. Second question is do I really need a physical partition (volume)(pv) for /boot or is it equally fine if I put it into a logical volume (lv) on top of a single shared volume group. Thanks in advance.

    Read the article

  • LINQ .Cast() extension method fails but (type)object works.

    - by Ben Robinson
    To convert between some LINQ to SQL objects and DTOs we have created explicit cast operators on the DTOs. That way we can do the following: DTOType MyDTO = (LinqToSQLType)MyLinq2SQLObj; This works well. However when you try to cast using the LINQ .Cast() extension method it trows an invalid cast exception saying cannot cast type Linq2SQLType to type DTOType. i.e. the below does not work List<DTO.Name> Names = dbContact.tNames.Cast<DTO.Name>() .ToList(); But the below works fine: DAL.tName MyDalName = new DAL.tName(); DTO.Name MyDTOName = (DTO.Name)MyDalName; and the below also works fine List<DTO.Name> Names = dbContact.tNames.Select(name => (DTO.Name)name) .ToList(); Why does the .Cast() extension method throw an invalid cast exception? I have used the .Cast() extension method in this way many times in the past and when you are casting something like a base type to a derived type it works fine, but falls over when the object has an explicit cast operator.

    Read the article

  • overloading "<<" with a struct (no class) cout style

    - by monkeyking
    I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

    Read the article

  • Why is T() = T() allowed?

    - by Rimo
    I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

    Read the article

  • Comparing objects and inheritance

    - by ereOn
    Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

    Read the article

  • Correct way to initialize dynamic Array in C++

    - by mef
    Hey guys, I'm currently working on a C++ project, where dynamic arrays often appear. I was wondering, what could be the correct way to initialize a dynamic array using the new-operator? A colleague of mine told me that it's a no-no to use new within the constructor, since a constructor is a construct that shouldn't be prone to errors or shouldn't fail at all, respectively. Now let's consider the following example: We have two classes, a more or less complex class State and a class StateContainer, which should be self-explained. class State { private: unsigned smth; public: State(); State( unsigned s ); }; class StateContainer { private: unsigned long nStates; State *states; public: StateContainer(); StateContainer( unsigned long n ); virtual ~StateContainer(); }; StateContainer::StateContainer() { nStates = SOME_DEFINE_N_STATES; states = new State[nStates]; if ( !states ) { // Error handling } } StateContainer::StateContainer( unsigned long n ) { nStates = n; try { states = new State[nStates] } catch ( std::bad_alloc &e ) { // Error handling } } StateContainer::~StateContainer() { if ( states ) { delete[] states; states = 0; } } Now actually, I have two questions: 1.) Is it ok, to call new within a constructor, or is it better to create an extra init()-Method for the State-Array and why? 2.) Whats the best way to check if new succeeded: if (!ptr) std::cerr << "new failed." or try { /*new*/ } catch (std::bad_alloc) { /*handling*/ } 3.) Ok its three questions ;o) Under the hood, new does some sort of ptr = (Struct *)malloc(N*sizeof(Struct)); And then call the constructor, right?

    Read the article

  • [javascript] Can I overload an object with a function?

    - by user257493
    Lets say I have an object of functions/values. I'm interested in overloading based on calling behavior. For example, this block of code below demonstrates what I wish to do. var main_thing = { initalized: false, something: "Hallo, welt!", something_else: [123,456,789], load: { sub1 : function() { //Some stuff }, sub2 : function() { //Some stuff }, all : function() { this.load.sub1(); this.load.sub2(); } } init: function () { this.initalized=true; this.something="Hello, world!"; this.something_else = [0,0,0]; this.load(); //I want this to call this.load.all() instead. } } The issue to me is that main_thing.load is assigned to an object, and to call main_thing.load.all() would call the function inside of the object (the () operator). What can I do to set up my code so I could use main_thing.load as an access the object, and main_thing.load() to execute some code? Or at least, similar behavior. Basically, this would be similar to a default constructor in other languages where you don't need to call main_thing.constructor(). If this isn't possible, please explain with a bit of detail.

    Read the article

  • Access to Perl's empty angle "<>" operator from an actual filehandle?

    - by Ryan Thompson
    I like to use the nifty perl feature where reading from the empty angle operator <> magically gives your program UNIX filter semantics, but I'd like to be able to access this feature through an actual filehandle (or IO::Handle object, or similar), so that I can do things like pass it into subroutines and such. Is there any way to do this? This question is particularly hard to google, because searching for "angle operator" and "filehandle" just tells me how to read from filehandles using the angle operator.

    Read the article

  • What do you call the << operator in Ruby when it's used for appending stuff?

    - by more or less
    In other contexts I know this << is called the bitshift operator. Is there a name for it when it's just used for append operations like you would do in an array or string (not sure what else you can append with it)? I'd like to be able to use an English word to refer to it instead of saying "you know, the operator with the two left arrows that's not really the left bitshift operator".

    Read the article

  • Who calls the Destructor of the class when operator delete is used in multiple inheritance.

    - by dicaprio-leonard
    This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

    Read the article

  • What version of mongodb was full $text query operator introduced?

    - by Marc Maxson
    Stupid question, right? But the official docs for 'text index' say: http://docs.mongodb.org/manual/core/index-text/ Text Indexes New in version 2.4. To perform queries that access the text index, use the $text query operator. Whereas if you click on the help for searching the index you created with the $text operator, it reads: http://docs.mongodb.org/manual/reference/operator/query/text/#op._S_text $text New in version 2.6. Seems to be 2.4 but still having problems wiht it.

    Read the article

  • How to write a cctor and op= for a factory class with ptr to abstract member field?

    - by Kache4
    I'm extracting files from zip and rar archives into raw buffers. I created the following to wrap minizip and unrarlib: Archive.hpp #include "ArchiveBase.hpp" #include "ArchiveDerived.hpp" class Archive { public: Archive(string path) { /* logic here to determine type */ switch(type) { case RAR: archive_ = new ArchiveRar(path); break; case ZIP: archive_ = new ArchiveZip(path); break; case UNKNOWN_ARCHIVE: throw; break; } } Archive(Archive& other) { archive_ = // how do I copy an abstract class? } ~Archive() { delete archive_; } void passThrough(ArchiveBase::Data& data) { archive_->passThrough(data); } Archive& operator = (Archive& other) { if (this == &other) return *this; ArchiveBase* newArchive = // can't instantiate.... delete archive_; archive_ = newArchive; return *this; } private: ArchiveBase* archive_; } ArchiveBase.hpp class ArchiveBase { public: // Is there any way to put this struct in Archive instead, // so that outside classes instantiating one could use // Archive::Data instead of ArchiveBase::Data? struct Data { int field; }; virtual void passThrough(Data& data) = 0; /* more methods */ } ArchiveDerived.hpp "Derived" being "Zip" or "Rar" #include "ArchiveBase.hpp" class ArchiveDerived : public ArchiveBase { public: ArchiveDerived(string path); void passThrough(ArchiveBase::Data& data); private: /* fields needed by minizip/unrarlib */ // example zip: unzFile zipFile_; // example rar: RARHANDLE rarFile_; } ArchiveDerived.cpp #include "ArchiveDerived.hpp" ArchiveDerived::ArchiveDerived(string path) { //implement } ArchiveDerived::passThrough(ArchiveBase::Data& data) { //implement } Somebody had suggested I use this design so that I could do: Archive archiveFile(pathToZipOrRar); archiveFile.passThrough(extractParams); // yay polymorphism! How do I write a cctor for Archive? What about op= for Archive? What can I do about "renaming" ArchiveBase::Data to Archive::Data? (Both minizip and unrarlib use such structs for input and output. Data is generic for Zip & Rar and later is used to create the respective library's struct.)

    Read the article

  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

    Read the article

  • Constructor is being invoked twice

    - by Knowing me knowing you
    In code: LINT a = "12"; LINT b = 3; a = "3";//WHY THIS LINE INVOKES CTOR? std::string t = "1"; //LINT a = t;//Err NO SUITABLE CONV FROM STRING TO LINT. Shouldn't ctor do it? #pragma once #include "LINT_rep.h" class LINT { private: typedef LINT_rep value_type; const value_type* my_data_; template<class T> void init_(const T&); public: LINT(const char* = 0); LINT(const std::string&); LINT(const LINT&); LINT(const long_long&); LINT& operator=(const LINT&); virtual ~LINT(void); LINT operator+()const; //DONE LINT operator+(const LINT&)const;//DONE LINT operator-()const; //DONE LINT operator-(const LINT&)const;//DONE LINT operator*(const LINT&)const;//DONE LINT operator/(const LINT&)const;///WAITS FOR APPROVAL LINT& operator+=(const LINT&);//DONE LINT& operator-=(const LINT&);//DONE LINT& operator*=(const LINT&);//DONE LINT operator/=(const LINT&);///WAITS FOR APPROVAL }; in line number 3 instead of assignment optor ctor is invoked. Why? I'm willing to uppload entire solution on some server otherwise it's hard to put everything in here. I can also upload video file. Another thing is that when I implement this assignment optor I'm getting an error that this optor is already in obj file? What's going on?

    Read the article

  • Adding a new operator symbol to a custom language in Notepad++?

    - by Wolfpack'08
    I'd like to create a custom operator for a custom language I'm highlighting in Notepad++. Has anyone done this in the past? A special character that often comes up in my language is the yen symbol (?), and I would like to highlight the phrases immediately following and immediately preceding that symbol; unfortunately, I cannot figure a way to add a custom operator, of it is even possible. Also, if anyone has any additional tag recommendations, please edit.

    Read the article

  • SQL SERVER – Puzzle Involving NULL – Resolve – Error – Operand data type void type is invalid for sum operator

    - by pinaldave
    Today is Monday let us start this week with interesting puzzle. Yesterday I had also posted quick question here: SQL SERVER – T-SQL Scripts to Find Maximum between Two Numbers Run following code: SELECT SUM(data) FROM (SELECT NULL AS DATA) t It will throw following error. Msg 8117, Level 16, State 1, Line 1 Operand data type void type is invalid for sum operator. I can easily fix if I use ISNULL Function as displayed following. SELECT SUM(data) FROM (SELECT ISNULL(NULL,0) AS DATA) t Above script will not throw an error. However, there is one more method how this can be fixed. Can you come up with another method which will not generate error? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

    Read the article

  • Is there a pattern or logical structure I can follow for Event Log Numbers?

    - by makerofthings7
    What are some ideas or structure I can use when assigning EventID to events that will be saved to the Event Log? Some options I've considered Sequential (0... int.Max) Multiple of 10, where the "0" is replaced with how noisy the debugLevel is set. xxx0 may represent exceptions, critical information, start, stop etc. ...? What numbering approach gives you the most insight when a user describes the event in an email or phone? What is the most useful to support staff?

    Read the article

  • Is there any logical relation between different types of UML diagrams?

    - by user363295
    I'm trying to find out ,that is there any relation between different types of UML diagrams, for example, once you developed a use case, should it be an event for each of them in a sequence diagram, or is there any exact relation between the use case and class diagrams. By the way my main focus is on the below diagrams: Use case class diagram activity sequence event if you think I need any extra diagram to be included so it can be used to connecting the above diagrams to each other, please mention it too. Thanks In Advance

    Read the article

  • Should interface only be used for behavior and not to show logical data grouped together?

    - by jags
    Should an interface only be used to specify certain behavior? Would it be wrong to use interface to group logically related data? To me it looks like we should not use interface to group logically related data as structure seems a better fit. A class may be used but class name should indicate something like DTO so that user gets the impression that class does not have any behavior. Please let me know if my assumption is correct. Also, are there any exceptions where interface can be used to group logically related data?

    Read the article

  • Does GetSystemInfo (on Windows) always return the number of logical processors?

    - by mhughes
    Reading up on this, and specifically reading the Microsoft docs, it looks like it should be returning the number of PHYSICAL processors, and that you should use GetLogicalProcessorInformation to figure out how many LOGICAL processors you have. Here's the doc I found on the SYSTEM_INFO structure: http://msdn.microsoft.com/en-us/library/ms724958(v=VS.85).aspx And here's the doc on GetLogicalProcessorInformation: (spaces added to get through spam filter) http:// msdn.microsoft.com/ en-us/ library/ ms683194.aspx Reading up on it further though, in most of the discussions I've found on this topic, developers say to that GetSystemInfo (and the SYSTEM_INFO structure) report the number of LOGICAL processors. When I search again, I find that MS did release some info on this (and a hot fix), here (spaces added to get through spam filter): http:// support. microsoft.com/ kb/936235 Reading that, it sounds like on Xp, pre-service Pack 3, GetSystemInfo reports the number of LOGICAL processors in the SYSTEM_INFO structure. It also reads to me that on Windows Vista and Windows 7, GetSystemInfo should be reporting the number of PHYSICAL processors (different to Windows XP pre-service Pack 3). Does anyone know what it actually does? Does GetSystemInfo really report the number of physical processors (on the same computer) differently, depending on which OS it's running on?

    Read the article

  • How to remove trailing spaces from SQL Server logical filename?

    - by Luke Girvin
    I'm dealing with a server running SQL Server 2000 SP1, and the logical filenames for one of the databases appear to contain trailing spaces. That is, this query: select replace(name, ' ', 'X') from sysfiles Returns the expected names plus a long string of Xs. How can I deal with this? I've tried running ALTER DATABASE... MODIFY FILE using the name (with and without spaces) and get an error message telling me the file does not exist.

    Read the article

  • How to list column headers of a SQL Server table using sp_help perhaps?

    - by Hamish Grubijan
    Hi, I have a few tables with 70-80 columns in them. I would like to populate them with somewhat random data, unless I will not be able to do so due to key violation, etc. The first step would be simply to get the list of all headers. There seem to be two ways: A) Run select * from table_of_interest; in MSFT SQL Server Management Studio 2008. Now, right-click the result and click "Copy With headers". However, I get zero rows back, and when I try to copy nothing + headers, I get: TITLE: Microsoft SQL Server Management Studio ------------------------------ Value cannot be null. Parameter name: data (System.Windows.Forms) ------------------------------ BUTTONS: OK ------------------------------ This looks like a bug ... anyhow ... there is another way. B) I can run sp_help table_of_interest;. However, I end up getting too much back. I get 7 different tables back but I am only interested in the second one. The columns of the second table are: Column_name | Type | Computed | Length | Prec | Scale | Nullable | TrimTrailingBlanks | FixedLenNullInSource | Collation I might be interested in just a Column_name and Type, but maybe other columns. So ... since sp_help probably runs a bunch of queries ... how do I get under the hood? How can I run the second query AND filter down the number of columns that I am interested in? Many Thanks!

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 30 31 32 33 34 35 36 37 38 39 40 41  | Next Page >