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  • Class template specializations with shared functionality

    - by Thomas
    I'm writing a simple maths library with a template vector type: template<typename T, size_t N> class Vector { public: Vector<T, N> &operator+=(Vector<T, N> const &other); // ... more operators, functions ... }; Now I want some additional functionality specifically for some of these. Let's say I want functions x() and y() on Vector<T, 2> to access particular coordinates. I could create a partial specialization for this: template<typename T> class Vector<T, 3> { public: Vector<T, 3> &operator+=(Vector<T, 3> const &other); // ... and again all the operators and functions ... T x() const; T y() const; }; But now I'm repeating everything that already existed in the generic template. I could also use inheritance. Renaming the generic template to VectorBase, I could do this: template<typename T, size_t N> class Vector : public VectorBase<T, N> { }; template<typename T> class Vector<T, 3> : public VectorBase<T, 3> { public: T x() const; T y() const; }; However, now the problem is that all operators are defined on VectorBase, so they return VectorBase instances. These cannot be assigned to Vector variables: Vector<float, 3> v; Vector<float, 3> w; w = 5 * v; // error: no conversion from VectorBase<float, 3> to Vector<float, 3> I could give Vector an implicit conversion constructor to make this possible: template<typename T, size_t N> class Vector : public VectorBase<T, N> { public: Vector(VectorBase<T, N> const &other); }; However, now I'm converting from Vector to VectorBase and back again. Even though the types are the same in memory, and the compiler might optimize all this away, it feels clunky and I don't really like to have potential run-time overhead for what is essentially a compile-time problem. Is there any other way to solve this?

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  • Web App fails when moved to production environment. Which server permissions do I need?

    - by Ashley Ward
    I have developed a small web app. This app allows users to upload images. It also produces text files with the names of those images (the names are stored and retrieved to/from an MySQL Database.) I have developed this app using MAMP. To create the uploaded image files I use the PHP function imagejpeg('my/path/name.jpg') and to delete the files I use the PHP function unlink('folder1/folder2/name.jpg') to write to the text document I am using the function fopen('folder1/folder2/name.txt', 'w') all three of these functions produce errors related to permissions - now the site has been moved to a live hosting environment. Why is this? and what permissions do I need to set the folder's folder1 and folder2 to? I know that permission 777 is generally bad because it opens up your server to the public. However what I have found is that the functions fail to work unless I use 777 on the folders. Can anyone shed any light on my dilemma?

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  • Why doesn't MySQL support millisecond precision?

    - by Byron Whitlock
    So I just found the most frustrating bug ever in MySQL. Apparently the TIMESTAMP field, and supporting functions do not support any greater precision than seconds!? So I am using PHP and Doctrine, and I really need those microseconds (I am using the actAs: [Timestampable] property). I found a that I can use a BIGINT field to store the values. But will doctrine add the milliseconds? I think it just assigns NOW() to the field. I am also worried the date manipulation functions (in SQL) sprinkled through the code will break. I also saw something about compiling a UDF extension. This is not an acceptable workaround because I or a future maintainer will upgrade and poof, change gone. Has anyone found a suitable workaround?

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  • BDD / TDD with JSpec - Removing code duplication

    - by Chetan
    How do I refactor to remove the code duplication in this spec: describe 'TestPlugins' describe '.MovieScanner(document)' before_each MoviePage_loggedIn = fixture("movie_logged_in.html") // Get logged-in movie page MoviePage_notloggedIn = fixture("movie_not_logged_in.html") // Get non logged-in movie page scanner = new MovieScanner() // Get movie scanner end it 'should scan logged-in movie page for movie data' doc = MoviePage_loggedIn // Get document to scan // Unit Tests // ------------------------------------------------------------ // Test movie scanner's functions scanner.getMovieTitle(doc).should.eql "The Jacket" scanner.getMovieYear(doc).should.eql "2005" // Test movie scanner's main scan function scannedData = scanner.scan(doc) scannedData.title.should.eql "The Jacket" scannedData.year.should.eql "2005" end it 'should scan non logged-in movie page for movie data' doc = MoviePage_notloggedIn // Get document to scan // Unit Tests // ------------------------------------------------------------ // Test movie scanner's functions scanner.getMovieTitle(doc).should.eql "The Jacket" scanner.getMovieYear(doc).should.eql "2005" // Test movie scanner's main scan function scannedData = scanner.scan(doc) scannedData.title.should.eql "The Jacket" scannedData.year.should.eql "2005" end end end

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  • A smoother alternative to jQuery show() and hide()

    - by David B
    I have a page setup with a hidden column using the jQuery show() and hide() functions to slide the column in and out. However it's kind of "clunky" and does not look very smooth when showing/hiding; in contrast I also have a section of the page using jquery UI accordion. When switching between these sections the transition looks very nice and smooth... Is there a better function than show()/hide() which looks as nice as the accordion does? (maybe the "easing" parameter can be used in the show/hide functions, but i'm not sure how to use this properly?)

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  • Is there any valid reason radians are used as the inputs to trig function in many modern languages?

    - by johnmortal
    Is there any pressing reason trig functions should use radian inputs in modern programming languages? As far as I know radians are typically ugly to deal with except in three cases: (1) You want to compute an arc length and you know the angle of the arc and (2) You need to do symbolic calculus with trig functions (3) certain infinite series expansion look prettier if the input is in radians. None of these scenarios seem like a worthy justification for every programming language I am familiar with using radian inputs for Sin, Cos, Tangent, etc... The third one sounds good because it might mean one gets faster computations using radians (very slightly faster- the cost of one additional floating point multiplication ) , but I am dubious even of that because most commonly the developer had to take an extra step to put the angle in radians in the first place. The other two are ridiculous justifications for all the added obscurity.

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  • Comparison between pointer and integer (cocoa)

    - by Cal S
    Hi, I'm just learning cocoa (coming from C#) but I'm getting a strange error for something that seems really simple... (charsSinceLastUpdate=36) #import "CSMainController.h" @implementation CSMainController //global vars int *charsSinceLastUpdate = 0; NSString *myString = @"Hello world"; // - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { ... } //other functions - (void)textDidChange:(NSNotification *)aNotification { NSLog(@"charsSinceLastUpdate=%i",charsSinceLastUpdate); if (charsSinceLastUpdate>=36) { // <- THIS line returns the error: Comparison between pointer and integer charsSinceLastUpdate=0; [statusText setStringValue:@"Will save now!"]; } else { charsSinceLastUpdate++; [statusText setStringValue:@"Not saving"]; } } //my functions - (void)showNetworkErrorAlert:(BOOL)showContinueWithoutSavingOption { ... } // @end Any help would be appreciated, thanks!

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  • Compare values in each column of two Oracle Types

    - by colinjameswebb
    I've been playing around with the pluto-test-framework today, and I'd like to get some existing functions into a test harness with it. I have lots of functions with this type of specification. FUNCTION DO_SOME_STUFF (pOldSchedule IN SCHEDULE_OBJ, pNewSchedule OUT SCHEDULE_OBJ, pLoggerContext IN OUT LOGGER_CONTEXT_OBJ) RETURN NUMBER; It takes pOldSchedule, does some stuff to it, and then returns pNewSchedule. The logger_context just does logging. As part of a test, I'd like to be able to compare the values in each of the columns of the type, without having to write individual IF statements. It'll need to return boolean to signify whether or not pOldSchedule and pNewSchedule match. Any ideas?

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  • The most elegant way to encapsulate WinAPI callbacks inside a class

    - by FractalizeR
    Hello. I am thinking about elegant way to encapsulate WinAPI callbacks inside a class. Suppose I am making a class handling asynchronous I/O. All Windows callbacks should be stdcall functions, not class methods (I need to pass their addresses to ReadFileEx WinAPI function for example). So, I cannot just pass method addresses as a callback routines to WinAPI functions. What is the most elegant way to encapsulate functionality of this type inside a class so that the class have events OnReadCompleted and OnWriteCompleted (I am using Delphi as a primary language, but I guess the situation must be the same in C++ because class methods are different from simple methods by the fact, that the first hidden parameter of them is this link. Of course this class is not a singleton and there can be many of them created by app at the same time. What do you think would be the good way to implement this?

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  • Trying to understand the usage of class_eval

    - by eMxyzptlk
    Hello everyone, I'm using the rails-settings gem, and I'm trying to understand how you add functions to ActiveRecord classes (I'm building my own library for card games), and I noticed that this gem uses one of the Meta-programming techniques to add the function to the ActiveRecord::Base class (I'm far from Meta-programming master in ruby, but I'm trying to learn it) module RailsSettings class Railtie < Rails::Railtie initializer 'rails_settings.initialize', :after => :after_initialize do Railtie.extend_active_record end end class Railtie def self.extend_active_record ActiveRecord::Base.class_eval do def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end end end What I don't understand is why he uses class_eval on ActiveRecord::Base, wasn't it easier if he just open the ActiveRecord::Base class and define the functions? Specially that there's nothing dynamic in the block (What I mean by dynamic is when you do class_eval or instance_eval on a string containing variables) something like this: module ActiveRecord class Base def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end I understand the second class_eval (before the def settings) is to define functions on the fly on every class that 'has_settings' right ? Same question here, I think he could use "def self.settings" instead of "class_eval.... def settings", no ?

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  • Trying to get simple jquery animations on a site I created in Dreamweaver

    - by JoeOzz
    Hey guys, another question. I'm trying to do some basic jQuery stuff for my final project. I'll be using it to modify my already existing site created in Dreamweaver a few months ago. However, no matter how I source the framework, it just won't take regardless of whether I host my own copy or link to someone else's like Google's. I'm including my jQuery function calls within my already existing .js file that includes some auto generated functions. I also tried creating a new .js specifically for my jQuery functions and still nothing. I realize this is vague, but any tips? Do I need another framework for jQuery to work off of to make animations like .fadeIn() or .slideDown()? Thanks guys and gals!

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  • How to override event on a UserControl

    - by Vadim
    Hello! I have a WinForms application (OwnerForm) with some UserControl. When textbox of UserControl is changed, I want to filter content of a OwnerForm. But how can I make it? I don't want to specify OwnerForm inside the user control. I know a solution to add manually handlers for MyUserControl.tb.TextChanged to some functions on a owner form, but I think it's bad way. I'll prefer to have overridable functions, but I can't imagine how to do it. Any suggestions? Thanks in advance,

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  • Hashing a python method to regenerate output when method is modified

    - by Seth Johnson
    I have a python method that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_method(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_method from time to time, but I would like to avoid having it run again while it's unchanged. [Time_consuming_method only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or a ridiculous idea? If this isn't a terrible idea, is the best implementation to write f = """ def ridiculous_method(): a = # # lots_of_computing_time return a """ , use the hashlib module to compute a hash for f, and use compile or eval to run it as code?

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  • Handling missing/incomplete data in R

    - by doug
    As you would expect from a DSL aimed at data analysts, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs, but if you want to deal with this before the function call, then: to replace each 'NA' w/ 0: ifelse(is.na(vx), 0, vx) to remove each 'NA': vx = vx[!is.na(a)] to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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  • The ultimate .NET file and directory utility library?

    - by Serge van den Oever
    I find myself writing file and directory utility functions all the time, and I was wondering if there is good file and directory library that already implements a more extensive set than available by default in System.IO. The kind of functions I'm looking for is things like: public static void GetTemporaryDirectory() { string tempDirectory = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName()); Directory.CreateDirectory(tempDirectory); return tempDirectory; } public static void CreateEmptyFile(string filename) { File.Create(filename).Dispose(); } public static void CreateEmptyFile(string path, string filename) { File.Create(Path.Combine(path, filename)).Dispose(); } public static void CreateDirectory(string path) { Directory.CreateDirectory(path); } public static void CreateDirectory(string path, string childpath) { Directory.CreateDirectory(Path.Combine(path, childpath)); }

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  • Learning to think in the Object Oriented Way

    - by SpikETidE
    Hi Everyone.... I am a programmer trying to learn to code in the object oriented paradigm... I mainly work with PHP and i thought of learning the zend framework... So, felt I need to learn to code in OO PHP.... The problem is, having done code using functions for quite a long time, i just can't get my head to think in the OO way.... Also felt that probably I am not the only one facing this problem since the beginning of time... So, how did you people learn object oriented programming... especially how did you succeed in "unlearning" to code using functions... and learn to see you code as objects...? Is there any good resource books or sites where one could find help...?? Thanks for sharing your knowledge and experiences...

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  • How to reference an anonymous JavaScript function?

    - by ProfK
    I'm trying to call a Page Method using a jQuery 'attached' event function, in which I like to use the closure to keep the event target local, as below, but page method calls declare several 'error' functions, and I would like to use one function for all of them. If, in the below code, I was handling an error and not success, how could I use my single, anonymous handler for all 3 error functions? $(":button").click(function () { var button = this; PageMethods.DoIt( function (a, b, c) { alert(button); }); }); This example passes an anonymous function for the success callback. There is only one of these. If I was passing an error callback, how could I use 'function (e, c, t)' for all 3 error callbacks?

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  • Converting C source to C++

    - by Barry Kelly
    How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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  • (Pathinfo vs fnmatch part 2) Speed benchmark reversed on Windows and Mac

    - by zaf
    On a previous question the pathinfo and fnmatch functions were benchmarked and the answers all came out opposite to my benchmark results. You can read the different results with the benchmark code here: http://stackoverflow.com/questions/2693428/pathinfo-vs-fnmatch I couldn't work it out until I ran the same code on a machine running vista. The results then matched the other users. My main machine is a mac. So, my questions are: Why do we get these two different results? Could this apply to other functions?

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  • Function Composition in C++

    - by Channel72
    There are a lot of impressive Boost libraries such as Boost.Lambda or Boost.Phoenix which go a long way towards making C++ into a truly functional language. But is there a straightforward way to create a composite function from any 2 or more arbitrary functions or functors? If I have: int f(int x) and int g(int x), I want to do something like f . g which would statically generate a new function object equivalent to f(g(x)). This seems to be possible through various techniques, such as those discussed here. Certainly, you can chain calls to boost::lambda::bind to create a composite functor. But is there anything in Boost which easily allows you to take any 2 or more functions or function objects and combine them to create a single composite functor, similar to how you would do it in a language like Haskell?

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  • SQL CLR and nullable datetime parameter

    - by toluca70
    I'm trying to write a SQLCLR function that takes a DateTime2 as input and returns another DateTime2. Based on this post I altered the parameter to be the C# type DateTime giving me the level of precision I require. However because the input can be null I would like it to be DateTime?; the return type as well. using System; using Microsoft.SqlServer.Server; namespace SqlServer.Functions { public class UserDefinedFunctions { [SqlFunction(DataAccess = DataAccessKind.None)] public static DateTime? GetLocalTimeFromGMT(DateTime? dateTime) { if (dateTime.HasValue) return DateTime.SpecifyKind(dateTime.Value, DateTimeKind.Utc).ToLocalTime(); else return (DateTime?)null; } } } The problem is I get the following error when I try to deploy: Error 1 Cannot find the type 'Nullable`1', because it does not exist or you do not have permission. SqlServer.Functions I'm using Sql Server 2008 and Visual Studio 2008.

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  • Calling a function that has 'Activity' as an argument.

    - by Andrew
    I have stripped down my functions for simplicity: public static int countLines(String fileName, Activity activity) throws IOException { BufferedReader in = new BufferedReader(new InputStreamReader(activity.getAssets().open(fileName))); return 3; } I am calling it from here: private CharSequence RandomRead() throws IOException { int numberLines = countLines("data.txt", ??????); return "Success" } In the call to countLines("data.txt", ??????), what do I put as the argument for the Activity? I've Googled all night and I can find no examples of an actual call to a function where Activity is an argument. (Lots of examples actually using 'activity', but no calls to the example functions). Thanks!

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  • Making a jQuery plugin work on all objects

    - by Jon Winstanley
    I am using the jQuery physics plugin for a pet project I am working on. The plugin enables the moving of DOM objects in realistic ways using velocity, gravity, wind etc. However I want to use the plugin to calculate where objects are to be placed inside a canvas element, not DOM objects. How do I change the plugin script functions to work on any object with 'top' and 'left' properties rather than only working with DOM objects: Currently the script functions look like this: jQuery.fn.funname = function() { return this; };

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