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  • Python list as *args?

    - by Cap
    I have two Python functions, both of which take variable arguments in their function definitions. To give a simple example: def func1(*args): for arg in args: print arg def func2(*args): return [2 * arg for arg in args] I'd like to compose them -- as in func1(func2(3, 4, 5)) -- but I don't want args in func1 to be ([6, 7, 8],), I want it to be (6, 7, 8), as if it was called as func1(6, 7, 8) rather than func1([6, 7, 8]). Normally, I would just use func1(*func2(3, 4, 5)) or have func1 check to see if args[0] was a list. Unfortunately, I can't use the first solution in this particular instance and to apply the second would require doing such a check in many places (there are a lot of functions in the role of func1). Does anybody have an idea how to do this? I imagine some sort of introspection could be used, but I could be wrong.

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  • Rails - eager load the number of associated records, but not the record themselves.

    - by Max Williams
    I have a page that's taking ages to render out. Half of the time (3 seconds) is spent on a .find call which has a bunch of eager-loaded associations. All i actually need is the number of associated records in each case, to display in a table: i don't need the actual records themselves. Is there a way to just eager load the count? Here's a simplified example: @subjects = Subject.find(:all, :include => [:questions]) In my table, for each row (ie each subject) i just show the values of the subject fields and the number of associated questions for each subject. Can i optimise the above find call to suit these requirements? I thought about using a group field but my full call has a few different associations included, with some second-order associations, so i don't think group by will work. @subjects = Subject.find(:all, :include => [{:questions => :tags}, {:quizzes => :tags}], :order => "subjects.name") :tags in this case is a second-order association, via taggings. Here's my associations in case it's not clear what's going on. Subject has_many :questions has_many :quizzes Question belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Quiz belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Grateful for any advice - max

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  • Need some help understanding this problem

    - by Legend
    I was wondering if someone could help me understand this problem. I prepared a small diagram because it is much easier to explain it visually. Problem I am trying to solve: 1. Constructing the dependency graph Given the connectivity of the graph and a metric that determines how well a node depends on the other, order the dependencies. For instance, I could put in a few rules saying that node 3 depends on node 4 node 2 depends on node 3 node 3 depends on node 5 But because the final rule is not "valuable" (again based on the same metric), I will not add the rule to my system. 2. Execute the request order Once I built a dependency graph, execute the list in an order that maximizes the final connectivity. First and foremost, I am wondering if I constructed the problem correctly and if I should be aware of any corner cases. Secondly, is there a closely related algorithm that I can look at? Currently, I am thinking of something like Feedback Arc Set or the Secretary Problem but I am a little confused at the moment. Any suggestions? PS: I am a little confused about the problem myself so please don't flame on me for that. If any clarifications are needed, I will try to update the question.

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  • ArrayList.Sort should be a stable sort with an IComparer but is not?

    - by Kaleb Pederson
    A stable sort is a sort that maintains the relative ordering of elements with the same value. The docs on ArrayList.Sort say that when an IComparer is provided the sort is stable: If comparer is set to null, this method performs a comparison sort (also called an unstable sort); that is, if two elements are equal, their order might not be preserved. In contrast, a stable sort preserves the order of elements that are equal. To perform a stable sort, you must implement a custom IComparer interface. Unless I'm missing something, the following testcase shows that ArrayList.Sort is not using a stable sort: internal class DisplayOrdered { public int ID { get; set; } public int DisplayOrder { get; set; } public override string ToString() { return string.Format("ID: {0}, DisplayOrder: {1}", ID, DisplayOrder); } } internal class DisplayOrderedComparer : IComparer { public int Compare(object x, object y) { return ((DisplayOrdered)x).DisplayOrder - ((DisplayOrdered)y).DisplayOrder; } } [TestFixture] public class ArrayListStableSortTest { [Test] public void TestWeblinkCallArrayListIsSortedUsingStableSort() { var call1 = new DisplayOrdered {ID = 1, DisplayOrder = 0}; var call2 = new DisplayOrdered {ID = 2, DisplayOrder = 0}; var call3 = new DisplayOrdered {ID = 3, DisplayOrder = 2}; var list = new ArrayList {call1, call2, call3}; list.Sort(new DisplayOrderedComparer()); // expected order (by ID): 1, 2, 3 (because the DisplayOrder // is equal for ID's 1 and 2, their ordering should be // maintained for a stable sort.) Assert.AreEqual(call1, list[0]); // Actual: ID=2 ** FAILS Assert.AreEqual(call2, list[1]); // Actual: ID=1 Assert.AreEqual(call3, list[2]); // Actual: ID=3 } } Am I missing something? If not, would this be a documentation bug or a library bug? Apparently using an OrderBy in Linq gives a stable sort.

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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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  • 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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  • 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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  • DIMMs: Single vs. Double vs. Quad Rank

    - by MikeyB
    What difference does the 'Rank' of DIMMs make to server memory? For example, when looking at server configurations I see the following being offered for the same server: 2GB (1x2GB) Single Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM 2GB (1x2GB) Dual Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM Given the option of Single Rank vs. Dual Rank or Dual Rank vs. Quad Rank is one always: Faster? Cheaper? Higher Bandwidth?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Can you create ACLs with open vSwitch on XenServer 5.6FP1 without using the DVS appliance?

    - by bwizzy
    I have a pool of XenServer hosts running the Free version of XenServer 5.6 FP1. I was wondering if I change the network backend to use Open vSwitch if I can specify ACLs on individual network VIFs without needing to use the DVS appliance (distributed virtual switch) which requires an Advanced License or higher. Basically I'm looking for a way to isolate VMs on my network so that if a user had root access on the command line they couldn't access other servers they should not be able to (without using a VLAN).

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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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  • Diagnostic high load sys cpu - low io

    - by incous
    A Linux server running Ubuntu 12.04 LTS with LAMP has a strange behaviour since last week: - cpu %sys higher than before, nearly equal %usr (before that, %sys just little compare with %usr) - IO reduce by half or 1/3 compare with the week before I try to diagnostic the process/cpu by some command (top/vmstat/mpstat/sar), and see that maybe it's a bit high on interrupt timer/resched. I don't know what that means, now open to any suggestion.

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  • Is there a compression method for compressing a group of very similar files, without archiving them?

    - by awiebe
    I want to compress a large nuber of files that have near identical headers, and also some data, however I do not wish to archive them, nor do I wish to zip them individually(because the copression ratio would be much higher if substitutions of similar blocks could be done using a single table). Does a compression method exist to do this already, or should I implement it myself. Note: Don't say "Disk space is cheap", because I may want to use this on an embedded system.

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  • LINQ to Entities question about orderby and null collections.

    - by Chevex
    I am currently developing a forum. I am new to LINQ and EF. In my forum I have a display that shows a list of topics with the most recent topics first. The problem is that "most recent" is relative to the topic's replies. So I don't want to order the list by the topic's posted date, rather I want to order the list by the topic's last reply's posted date. So that topics with newer replies pop back to the top of the list. This is rather simple if I knew that every topic had at least one reply; I would just do this: var topicsQuery = from x in board.Topics orderby x.Replies.Last().PostedDate descending select x; However, in many cases the topic has no replies. In which case I would like to use the topic's posted date instead. Is there a way within my linq query to order by x.PostedDate in the event that the topic has no replies? I'm getting confused by this and any help would be appreciated. With the above query, it breaks on topics with no replies because of the x.Replies.Last() which assumes there are replies. LastOrDefault() doesn't work because I need to access the PostedDate property which also assumes a reply exists. Thanks in advance for any insight.

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  • What is the best way to identify which form has been submitted?

    - by Rupert
    Currently, when I design my forms, I like to keep the name of the submit button equal to the id of the form. Then, in my php, I just do if(isset($_POST['submitName'])) in order to check if a form has been submitted and which form has been submitted. Firstly, are there any security problems or design flaws with this method? One problem I have encountered is when I wish to overlay my forms with javascript in order to provide faster validation to the user. For example, whilst I obviously need to retain server side validation, it is more convenient for the user if an error message is displayed inline, upon blurring an input. Additionally, it would be good to provide entire form validation, upon clicking the submit button. Therefore, when the user clicks on the form's submit button, I am stopping the default action, doing my validation, and then attempting to renable the traditional submit functionality, if the validation passes. In order to do this, I am using the form.submit() method but, unfortunately, this doesn't send the submit button variable (as it should be as form.submit() can be called without any button being clicked). This means my PHP script fails to detect that the form has been submitted. What is the correct way to work around this? It seems like the standard solution is to add a hidden field into the form, upon passing validation, which has the name of form's id. Then when form.submit() is called, this is passed along in place of the submit button. However, this solution seems very ungraceful to me and so I am wondering whether I should: a) Use an alternative method to detect which form has been submitted which doesn't rely rely on passing the submit button. If so what alternative is there? Obviously, just having an extra hidden field from the start isn't any better. b) Use an alternative Javascript solution which allows me to retain my non-Javascript design. For example, is there an alternative to form.submit() which allows me to pass in extra data? c) Suck it up and just insert a hidden field using Javascript.

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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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  • What advantage does a 2400x600 dpi printer have over a 1200x1200 dpi printer?

    - by Cygon
    I've seen laser printers with a resolutions of 1200x1200 dpi and, strangely, 2400x600 dpi. As the measure is dots per inch, not Kdots on a page or something (where a higher vertical resolution might make sense because paper is rectangular, not square), I'm wondering what the uneven resolution is good for. Why print one square inch with 2400 dots vertically but only 600 horizontally? Does this look more detailed than 1200 by 1200 dots? Or is it better for textile printing or some other special case?

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