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• Fast comparison of char arrays?

  - by StackedCrooked

  I'm currently working in a codebase where IPv4 addresses are represented as pointers to u_int8. The equality operator is implemented like this: bool Ipv4Address::operator==(const u_int8 * inAddress) const { return (*(u_int32*) this->myBytes == *(u_int32*) inAddress); } This is probably the fasted solution, but it causes the GCC compiler warning: ipv4address.cpp:65: warning: dereferencing type-punned pointer will break strict-aliasing rules How can I rewrite the comparison correctly without breaking strict-aliasing rules and without losing performance points? I have considered using either memcmp or this macro: #define IS_EQUAL(a, b) \ (a[0] == b[0] && a[1] == b[1] && a[2] == b[2] && a[3] == b[3]) I'm thinking that the macro is the fastest solution. What do you recommend?

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• How to save an order (permutation) in an sql db

  - by Bendlas

  I have a tree structure in an sql table like so: CREATE TABLE containers ( container_id serial NOT NULL PRIMARY KEY, parent integer REFERENCES containers (container_id)) Now i want to define an ordering between nodes with the same parent. I Have thought of adding a node_index column, to ORDER BY, but that seem suboptimal, since that involves modifying the index of a lot of nodes when modifying the stucture. That could include adding, removing, reordering or moving nodes from some subtree to another. Is there a sql datatype for an ordered sequence, or an efficient way to emulate one? Doesn't need to be fully standard sql, I just need a solution for mssql and hopefully postgresql EDIT To make it clear, the ordering is arbitrary. Actually, the user will be able to drag'n'drop tree nodes in the GUI

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• Are C++ Templates just Macros in disguise?

  - by Roddy

  I've been programming in C++ for a few years, and I've used STL quite a bit and have created my own template classes a few times to see how it's done. Now I'm trying to integrate templates deeper into my OO design, and a nagging thought keeps coming back to me: They're just a macros, really... You could implement (rather UGLY) auto_ptrs using #defines, if you really wanted to. This way of thinking about templates helps me understand how my code will actually work, but I feel that I must be missing the point somehow. Macros are meant evil incarnate, yet "template metaprogramming" is all the rage. So, what ARE the real distinctions? and how can templates avoid the dangers that #define leads you into, like Inscrutable compiler errors in places where you don't expect them? Code bloat? Difficulty in tracing code? Setting Debugger Breakpoints?

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• g++ no matching function call error

  - by gufftan

  I've got a compiler error but I can't figure out why. the .hpp: #ifndef _CGERADE_HPP #define _CGERADE_HPP #include "CVektor.hpp" #include <string> class CGerade { protected: CVektor o, rv; public: CGerade(CVektor n_o, CVektor n_rv); CVektor getPoint(float t); string toString(); }; the .cpp: #include "CGerade.hpp" CGerade::CGerade(CVektor n_o, CVektor n_rv) { o = n_o; rv = n_rv.getUnitVector(); } the error message: CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&) CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&)

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• Objective C - Custom Getter with inheritance

  - by anhdat

  Recently I have worked with Core Data. When I want to set a default value for some fields, I came up with this problem: So I made a simple represent: We have 2 class Parent and Child, in which Child inherit from Parent. // Parent.h @interface Parent : NSObject @property (strong, nonatomic) NSString *lastName; // Child.h @interface Child : Parent In Parent class, I made a custom getter to set a default value when nothing is set: // Parent.h - (NSString *)lastName { if (_lastName) { return _lastName; } else { return @"Parent Default Name"; } } But I cannot make a custom default value for the field "name" which Child inherits from its Parent. // Child.h @implementation Child - (NSString *)lastname { if (super.lastName) { return super.lastName; } else { return @"Child Default Name"; } } Apparently, this method is never called. So my question here is: How can I set a custom getter for the field the Child class inherits from Parent without define an overriding property?

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• Cartesian Plane

  - by NuNu

  I'm trying to define a function in Haskell that takes an integer argument c and returns the list of all points on the cartesian plane of the form (x/c,y/c) where x and y are integers. x/c is between -2 and 1 and y/r is between -1 and 1 This is what I've gotten so far which I'm almost sure is right but I'm getting a parse error on input = when I run it particularly at this line: cart xs ys c = [(y/c,x/c) | x <- xs, y <- ys] plane :: Int -> [a] plane c = cart [-1*c .. 1*c] [-2*c .. 1*c] c cart xs ys c = [(y/c,x/c) | x <- xs, y <- ys] A sample output would be: plane 1 would generate: [(-2.0, -1.0), (-1.0, -1.0), ( 0.0, -1.0), ( 1.0, -1.0), (-2.0, 0.0), (-1.0, 0.0), ( 0.0, 0.0), ( 1.0, 0.0), (-2.0, 1.0), (-1.0, 1.0), ( 0.0, 1.0), ( 1.0, 1.0)] Anyone have any idea how I can fix this! Thanks

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• Doubt about a particular pattern of Javascript class definition

  - by fenderplayer

  Recently i saw the following code that creates a class in javascript: var Model.Foo = function(){ // private stuff var a, b; // public properties this.attr1 = ''; this.attr2 = ''; if(Model.Foo._init === 'undefined'){ Model.Foo.prototype = { func1 : function(){ //...}, func2 : function(){ //... }, //other prototype functions } } Model.Foo._init = true; } // Instantiate and use the class as follows: var foo = new Model.Foo(); foo.func1(); I guess the _init variable is used to make sure we don't define the prototypes again. Also, i feel the code is more readable since i am placing everything in a function block (so in oop-speak, all attributes and methods are in one place). Do you see any issues with the code above? Any pitfalls of using this pattern if i need to create lots of classes in a big project?

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• How do I return the indices of a multidimensional array element in C?

  - by Eddy

  Say I have a 2D array of random boolean ones and zeroes called 'lattice', and I have a 1D array called 'list' which lists the addresses of all the zeroes in the 2D array. This is how the arrays are defined: define n 100 bool lattice[n][n]; bool *list[n*n]; After filling the lattice with ones and zeroes, I store the addresses of the zeroes in list: for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { if(!lattice[i][j]) // if element = 0 { list[site_num] = &lattice[i][j]; // store address of zero site_num++; } } } How do I extract the x,y coordinates of each zero in the array? In other words, is there a way to return the indices of an array element through referring to its address?

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• Does XSD allow simpleContent and complexContent at the same time?

  - by Willi Schönborn

  I want to write an xsd for the xmlrpc spec (and generate java classes out of it using jaxb). The xmlrpc spec allows values like: <value><int>123</int></value> <value><boolean>1</boolean></value> But at the same time it requires: If no type is indicated, the type is string. Which means i could receive something like this: <value>test123</value> which is equivalent to <value><string>test123</string></value> Is there a way to define this in an xsd.

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• Does Visual Studio 2010 support something like Eclipse's "Generate delegate methods"?

  - by devoured elysium

  Eclipse allows us to define a class as: interface MyInterface { void methodA(); int methodB(); } class A : MyInterface { MyInterface myInterface; } and then with this "Generate delegate methods", it will implement all needed methods for the interface, redirecting their logic to myInterface's methods: class A : MyInterface { MyInterface myInterface; public void methodA() { myInterface.methodA(); } public int methodB() { return myInterface.methodB(); } } Is it possible to accomplish the same with VS2010? And with R#? Thanks

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• Tools for understanding large codebase

  - by 0tar0gz

  Hi! My whole life I have been programming in simple plain text editor. Lately, I was contemplating about joining an open source project which is fairly large and written in C. I downloaded the sources, started to look around, read this, forget that... Then I thought to myself: this can't be true. This is 21st century there must be some tool which would help me to understand the code, perhaps some kind of IDE or "code navigator". What flows from here to where, this typedef struct is just interface to that private type, this function is just #define from above, function called in this file is defined in that file, ... you get the idea. Dear Stack Overflow, is this 21st century? Is there something like this?

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• Ruby on Rails: Modules vs. Classes

  - by Jack

  I'm trying to add a function that will be accessible throughout all parts of my program. I want something like: def GlobalFunctions.my_function(x,y) puts x + y end to be accessible for all models. Specifically I am trying to use a function like this in my seeds.rb file but I am most likely going to be reusing the code and don't want any redundancy. Now I know I can make a simple class, but I could also make a module. What are some reasons to go in either direction? And once I've decided on which type to use, how do I make it accessible throughout the whole program? I have tried a module, but I keep getting " Expected app/[module file] to define [ModuleName]"

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• [Perl] Use a Module / Object which is defined in the same file

  - by Robert S. Barnes

  I need to define some modules and use them all in the same file. No, I can't change the requirement. I would like to do something like the following: { package FooObj; sub new { ... } sub add_data { ... } } { package BarObj; use FooObj; sub new { ... # BarObj "has a" FooObj my $self = ( myFoo => FooObj->new() ); ... } sub some_method { ... } } my $bar = BarObj->new(); However, this results in the message: Can't locate FooObj.pm in @INC ... BEGIN failed... How do I get this to work?

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• Which HRESULT literal constant will fail the SUCCEEDED() macro?

  - by Hamish Grubijan

  Definition of SUCCEEDED(): #define SUCCEEDED(hr) (((HRESULT)(hr)) >= 0) Background: When an Ok button is clicked on a dialog, I need to return an HRESULT value hr such that SUCCEEDED(hr) is true. If Cancel button is clicked, I need to return a negative value. I could have used bools, but that would break the existing pattern (usually the hr values come from depths of system dlls). So, I know I can return S_OK on Ok, but what do I return on Cancel? I could just return (HRESULT)-1;, but there must be a better way - some HRESULT literal constant which has negative value and represents a generic failure. S_FALSE is not it, for it's value is defined as 1L. Please help me find the right constant.

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• Mapping LINQ to SQL table to another very similar table without iterating through every one

  - by Daniel Coffman

  Apologies for the vague question. Here it is: I have a table object created by LINQ to SQL. I am copying entries from one table to an "archive" table that has all the columns of the original, plus a couple extra ones. It feels sloppy to iterate through every object and manually define the mapping like: foreach (oldTable in dbContextOldTables) { var newTable = new NewTable(); newTable.TableID = oldTable.ID; newTable.Title = oldTable.Title; ... (repeat for twenty columns) newTable.ColumnThatIsntInOldTable = "Data that will be the same for every row"; dbContext.NewTables.InsertOnSubmit(newTable); } dbContext.SubmitChanges(); Is there a clever way to do this?

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• Where should I set the DataContext - code behind or xaml?

  - by dovholuk

  (honestly I searched and read all the 'related questions' that seemed relevant - i do hope i didn't "miss" this question from elsewhere but here goes...) There are two different ways (at least) to set the DataContext. One can use XAML or one can use the code behind. What is the 'best practice' and why? I tend to favor setting it in XAML because it allows a designer to define collections on their own but I need 'ammunition' on why it's a best practice or why I'm crazy and the code behind is the bomb...

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• Rails 2.3.5: How does one access code inside of lib/directory/file.rb?

  - by randombits

  I created a file so I can share a method amongst many models in lib/foo/bar_woo.rb. Inside of bar_woo.rb I defined the following: module BarWoo def hello puts "hello" end end Then in my model I'm doing something like: def MyModel < ActiveRecord::Base include Foo::BarWoo def some_method Foo::BarWoo.hello end end The interpreter is complaining that it expected bar_woo.rb to define Foo::BarWoo. The Agile Web Development with Rails book states that if files contain classes or modules and the files are named using the lowercase form of the class or module name, then Rails will load the file automatically. I didn't require it because of this.

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• Beginner's Question about accessing mysql using OOP

  - by user345690

  I am reading the PHP and mySQL web development book and so far been doing all the PHP and mysql using procedural. But then it talks about accessing mysql with objects. This works for me: //I define $db so can connect $query="select * FROM testing"; $result=mysqli_query($db,$query); while($row=mysqli_fetch_array($result)){ //echo the data } But when I try to do it with classes, it doesn't $query="select * FROM testing"; $result=$db->query($query); $row=$result->fetch_assoc(); Do I have to write my own class so it defines what query and fetch_assoc does? Or what?

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• problem with exporting a customized form from dll

  - by mavric

  I'm working on an application so i have write an dll which contain a form with some additional work and methods. so in the beginning of my program the thread launch this form (from my dll) to get some informations and then hide it and initialize some components and the application form and then show it. when the thread come the line where it define new instance of the exported form "MyForm inputform = new MyForm();" it throw an Exception called "Top-level control cannot be added to a control." so i don't know what to do ?!!. i tried to take the code of the form from the dll source code and put it in the main program and it works.... .but still i want to know what happen and what impede my application from run that form from my dll. thanks.

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• Re-use aliased field in SQL SELECT STATEMENT

  - by Bad Display Name

  Hi, the question is hard to define without giving an example, e.g. I'd like to achieve something like this : SELECT (CASE WHEN ...) AS FieldA, 20 + FieldA AS FieldB FROM Tbl Assuming that by "..." I've replaced a long and complex CASE statement, hence I don't want to repeat it when selecting FieldB and use the aliased FieldA instead. IS THIS EVEN POSSIBLE? What could be a workaround? Note, that this will return multiple rows , hence the DECLARE/SET outside the SELECT statement is no good in my case. PLEASE HELP. P.S. I am using SQL 2008

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• Using iPhone Core Data to many Relationship

  - by BLeB

  When I define a to many relationship between entities in Xcode and then generate the data class from the entity I get a header with the following methods defined: @interface PriceList (CoreDataGeneratedAccessors) - (void)addItemsObject:(PriceListItem *)value; - (void)removeItemsObject:(PriceListItem *)value; - (void)addItems:(NSSet *)value; - (void)removeItems:(NSSet *)value; @end When I attempt to call addItemsObject with the following code a doesNotRecognizeSelector exception is thrown. PriceListItem *item = [NSEntityDescription insertNewObjectForEntityForName:@"PriceListItem" inManagedObjectContext:managedObjectContext]; item.cat = [attributeDict valueForKey:@"c"]; item.sel = [attributeDict valueForKey:@"s"]; [self addItemsObject:item]; From what I have read I do not have to implement these methods and that they are generated at runtime. Any ideas?

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• Gaining Reference to the Dialog from Dialog content

  - by coffeeaddict

  Here's my scenario: I've got a div on Page A. When an event happens (whatever I define, a click, whatever), I do a div.Dialog, set its properties and open it The data inside is returned from an async .ajax call that grabs the data from a url and appends it to the div by calling div.html(data) inside the .ajax callback, so it's essentially loading a PageB by getting the data (content) and appending it to the div that's calling the dialog("open")...nothing special here I don't think. My question: In Page B, how do I reference the dialog so I can do some things to it? For instance in Page B's content that I received back from that .ajax call and added to the div via .html(data), there is a button and when clicked I need to close the dialog. Right now my buttons are not working because one of them closes out the dialog and the other should redirect to a new page but both do not work now because I have no reference to the dialog that it's in to manipulate it.

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• Why is my upload-of-a-file code putting 2 sets of files into my directory? (PHP)

  - by ggfan

  When I upload a file using this code, it puts a copy of the file in the "uploads" folder(which is what I want) but it also puts a copy in my root. I only want the files going to the uploads folder. define ('GW_UPLOADPATH', 'uploads/'); $upfile= GW_UPLOADPATH . $_FILES['userfile']['name']; if(is_uploaded_file($_FILES['userfile']['tmp_name'])) { if(!move_uploaded_file($_FILES['userfile']['tmp_name'], $upfile)) //this is saying if the file isn't moved to $upfile. { echo 'Problem: could not move file to destination directory'; exit; } } else { echo 'Problem: Possible file upload attack. Filename: '; //this could be an attack b/c it might be from localhost. echo $_FILES['userfile']['name']; exit; } echo 'File uploaded successfully<br><br>';

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• Offsite data storage for simple app, or a similar supported persistence mechanism?

  - by jdk

  Question Is there a usable facebook entry point to the Data Storage API that facebook lists on their app admin page for developers, or should I consider an alternate mechanism? What alternative mechanisms exist to simply persist my information offsite (away from my server app) without stuffing it into a cookie that's prone to expire? ... Background The facebook Data Store Admin tool is made available in a facebook App's Settings as seen here: (continue reading below) However when I visit the DataStoreAdmin link nothing works (i.e. clicking the buttons to define the data store types and objects does nothing - I have tried different browsers). The Wiki page for Data Store API hasn't been updated recently and the second last update says the beta Data Store was taken offline. It seems odd the link would be readily available and highly visible at the top of the App configuration area if indeed it's defunct. I was hoping some kind of key/value pair solution to remove the data calls from my own server.

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• What is CSS? what should be the shortest and appropriate answer of this question? [closed]

  - by metal-gear-solid

  What is CSS? what should be the shortest and appropriate answer of this question? How simple we can explain , What is CSS ,just in words? mine answer is this Stands for "Cascading Style Sheet." Cascading style sheets are used to format the layout of Web pages. They can be used to define text styles, table sizes, and other aspects of Web pages that previously could only be defined in a page's HTML. Is it ok or it can be more perfect or shorten?

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