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• How can you transform a set of numbers into mostly whole ones?

  - by Alice

  Small amount of background: I am working on a converter that bridges between a map maker (Tiled) that outputs in XML, and an engine (Angel2D) that inputs lua tables. Most of this is straight forward However, Tiled outputs in pixel offsets (integers of absolute values), while Angel2D inputs OpenGL units (floats of relative values); a conversion factor between these two is needed (for example, 32px = 1gu). Since OpenGL units are abstract, and the camera can zoom in or out if the objects are too small or big, the actual conversion factor isn't important; I could use a random number, and the user would merely have to zoom in or out. But it would be best if the conversion factor was selected such that most numbers outputted were small and whole (or fractions of small whole numbers), because that makes it easier to work with (and the whole point of the OpenGL units is that they are easy to work with). How would I find such a conversion factor reliably? My first attempt was to use the smallest number given; this resulted in no fractions below 1, but often lead to lots of decimal places where the factors didn't line up. Then I tried the mode of the sequence, which lead to the largest number of 1's possible, but often lead to very long floats for background images. My current approach gets the GCD of the whole sequence, which, when it works, works great, but can easily be thrown off course by a single bad apple. Note that while I could easily just pass the numbers I am given along, or pick some fixed factor, or use one of the conversions I specified above, I am looking for a method to reliably scale this list of integers to small, whole numbers or simple fractions, because this would most likely be unsurprising to the end user; this is not a one off conversion. The end users tend to use 1.0 as their "base" for manipulations (because it's simple and obvious), so it would make more sense for the sizes of entities to cluster around this.

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• ObjectDisposedException when .Show()'ing a form that shouldn't be disposed.

  - by user320781

  ive checked out some of the other questions and obviously the best solution is to prevent the behavior that causes this issue in the first place, but the problem is very intermittent, and very un-reproduceable. I basically have a main form, with sub forms. The sub forms are shown from menus and/or buttons from the main form like so: private void myToolStripMenuItem_Click(object sender, EventArgs e) { try { xDataForm.Show(); xDataForm.Activate(); } catch (ObjectDisposedException) { MessageBox.Show("ERROR 10103"); ErrorLogging newLogger = new ErrorLogging("10103"); Thread errorThread = new Thread(ErrorLogging.writeErrorToLog); errorThread.Start(); } } and the sub forms are actually in the main form(for better or worse. i would actually like to change this but would be a considerable amount of time to do so): public partial class FormMainScreen : Form { Form xDataForm = new xData(); ...(lots more here) public FormMainScreen(int pCount, string pName) { InitializeComponent(); ... } ... } The Dispose function for the sub form is modified so that, the 'close' and 'X' buttons actually hide the form so we dont have to re-create it every time. When the main screen closes, it sets a "flag" to 2, so the other forms know that it is actually ok to close; protected override void Dispose(bool disposing) { if (FormMainScreen.isExiting == 2) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } else { if (xData.ActiveForm != null) { xData.ActiveForm.Hide(); } } } So, the question is, why would this work over and over and over again flawlessly, but, literally, about every 1/1000 of the time, cause an exception, or rather, why is my form being disposed? I had a suspicion that the garbage collector was getting confused, because it occurs slightly more frequently after it has been running for many hours.

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• Constructor and Destructors in C++ [Not a question] [closed]

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Need help with a SQL CTE Query

  - by Chuck

  I have a table that I need to get some specific data from for a view. Here's the base table structure with some sample data: | UserID | ReportsToUserID | Org ID | ------------------------------------- | 1 | NULL | 1 | ------------------------------------- | 2 | 1 | 1 | ------------------------------------- | 3 | 2 | 1 | ------------------------------------- | 4 | 3 | 1 | ------------------------------------- The users will be entering reports and users can see the reports of users who report to them and any users who report to those users. Users who report to no one can see everything in their organization Given my sample data above, user 1 can see the reports of 2, 3, & 4; user 2 can see the reports of 3 & 4; and user 3 can see the reports of 4. For the view, I'd like to have the data returned as follows: | UserID | CanSeeUserID | OrgID | -------------------------------------------- | 1 | 2 | 1 | -------------------------------------------- | 1 | 3 | 1 | -------------------------------------------- | 1 | 4 | 1 | -------------------------------------------- | 2 | 3 | 1 | -------------------------------------------- etc... Below is my current code, any help is greatly appreciated. WITH CTEUsers (UserID, CanSeeUserID, OrgID) AS ( SELECT e.ID, e.ReportsToUserID, e.OrgID FROM Users e WITH(NOLOCK) WHERE COALESCE(ReportsToUserID,0) = 0 --ReportsToUserID can be NULL or 0 UNION ALL SELECT e.ReportsToUserID, e.ID,e.OrgID FROM Users e WITH(NOLOCK) JOIN CTEUsers c ON e.ID = c.UserID ) SELECT * FROM CTEUsers

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• jQuery $.getJSON - How do I parse a flickr.photos.search REST API call?

  - by Chad

  Trying to adapt the $.getJSON Flickr example: $.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?tags=cat&tagmode=any&format=json&jsoncallback=?", function(data){ $.each(data.items, function(i,item){ $("<img/>").attr("src", item.media.m).appendTo("#images"); if ( i == 3 ) return false; }); }); to read from the flickr.photos.search REST API method, but the JSON response is different for this call. Click here to see the JSON response. This is what I've done so far: var url = "http://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=9322c53dde3b36bda33f79c16bb99104&tags=yokota+air+base&safe_search=1&per_page=20"; var src; $.getJSON(url + "&format=json&jsoncallback=?", function(data){ $.each(data.photos, function(i,item){ src = "http://farm"+ item.photo.farm +".static.flickr.com/"+ item.photo.server +"/"+ item.photo.id +"_"+ item.photo.secret +"_m.jpg"; $("<img/>").attr("src", src).appendTo("#images"); if ( i == 3 ) return false; }); }); I guess I'm not building the image src correctly. Couldn't find any documentation on how to build the image src, based on what the JSON response is. How do you parse a flickr.photos.search REST API call?

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• How do you parse the XDG/gnome/kde menu/desktop item structure in c++??

  - by Joe Soul-bringer

  I would like to parse the menu structure for Gnome Panels (the standard Gnome Desktop application launcher) and it's KDE equivalent using c/c++ function calls. That is, I'd like a list of what the base menu categories and submenu are installed in a given machine. I would like to do with using fairly simple c/c++ function calls (with NO shelling out please). I understand that these menus are in the standard xdg format. I understand that this menu structure is stored in xml files such as: /home/user/.config/menus/applications.menu I've look here: http://www.freedesktop.org/wiki/Specifications/menu-spec?action=show&redirect=Standards%2Fmenu-spec but all they offer is the standard and some shell files to insert item entries (I don't want shell scripts, I don't want installation, I definitely don't want to create a c-library from the XDG specification. I want to find the existing menu structure). I've looked here: http://library.gnome.org/admin/system-admin-guide/stable/menustructure-13.html.en for more notes on these structures. None of this gives me a good idea of how determine the menu structures using a c/c++ program. The actual gnome menu structures seem to be a horrifically hairy things - they don't seem to show the menu structure but to give an XML-coded description of all the changes that the menus have gone through since installation. I assume gnome panels parses these file so there's a function buried somewhere to do this but I've yet to find where that function is after scanning library.gnome.org for a couple of days. I've scanned the Nautilus source code as well but Panels seem to exist elsewhere or are burried well. Thanks in advance

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• How to populate a listview in ASP.NET 3.5 through a dataset?

  - by EasyDot

  Is it possible to populate a listview with a dataset? I have a function that returns a dataset. Why im asking this is because my SQL is quite complicated and i can't convert it to a SQLDataSource... Public Function getMessages() As DataSet Dim dSet As DataSet = New DataSet Dim da As SqlDataAdapter Dim cmd As SqlCommand Dim SQL As StringBuilder Dim connStr As StringBuilder = New StringBuilder("") connStr.AppendFormat("server={0};", ConfigurationSettings.AppSettings("USERserver").ToString()) connStr.AppendFormat("database={0};", ConfigurationSettings.AppSettings("USERdb").ToString()) connStr.AppendFormat("uid={0};", ConfigurationSettings.AppSettings("USERuid").ToString()) connStr.AppendFormat("pwd={0};", ConfigurationSettings.AppSettings("USERpwd").ToString()) Dim conn As SqlConnection = New SqlConnection(connStr.ToString()) Try SQL = New StringBuilder cmd = New SqlCommand SQL.Append("SELECT m.MESSAGE_ID, m.SYSTEM_ID, m.DATE_CREATED, m.EXPIRE_DATE, ISNULL(s.SYSTEM_DESC,'ALL SYSTEMS') AS SYSTEM_DESC, m.MESSAGE ") SQL.Append("FROM MESSAGE m ") SQL.Append("LEFT OUTER JOIN [SYSTEM] s ") SQL.Append("ON m.SYSTEM_ID = s.SYSTEM_ID ") SQL.AppendFormat("WHERE m.SYSTEM_ID IN ({0}) ", sSystems) SQL.Append("OR m.SYSTEM_ID is NULL ") SQL.Append("ORDER BY m.DATE_CREATED DESC; ") SQL.Append("SELECT mm.MESSAGE_ID, mm.MODEL_ID, m.MODEL_DESC ") SQL.Append("FROM MESSAGE_MODEL mm ") SQL.Append("JOIN MODEL m ") SQL.Append(" ON m.MODEL_ID = mm.MODEL_ID ") cmd.CommandText = SQL.ToString cmd.Connection = conn da = New SqlDataAdapter(cmd) da.Fill(dSet) dSet.Tables(0).TableName = "BASE" dSet.Tables(1).TableName = "MODEL" Return dSet Catch ev As Exception cLog.EventLog.logError(ev, cmd) Finally 'conn.Close() End Try End Function

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• Modelling deterministic and nondeterministic data separately

  - by Superstringcheese

  I'm working with the Microsoft ADO.NET Entity Framework for a game project. Following the advice of other posters on SO, I'm considering modelling deterministic and nondeterministic data separately. The idea for this came from a discussion on multiplayer games, but it seemed to make sense in a single-player scenario as well. Deterministic (things that aren't going to change during gameplay) Attributes (Strength, Agility, etc.) and their descriptions Skills and their descriptions and requirements Races, Factions, Equipment, etc. Base Attribute/Skill/Equipment loadouts for monsters Nondeterministic (things that will change a lot during gameplay) Beings' current AttributeModifers (Potion of Might = +10 Strength), current health and mana, etc. Player inventory, cash, experience, level Player quests states Player FactionRelationships ...and so on. My deterministic model would serve as a set of constants. My nondeterministic model would provide my on-the-fly operable data and would be serialized to a savegame file to maintain game state between play sessions. The data store will be an embedded SQL Compact database. So I might want to create relations between my Attributes table (deterministic model) and my BeingAttributeModifiers table (nondeterministic model), but how do I set that up across models? Det model/db Nondet model/db ____________ ________________________ |Attributes | |PlayerAttributeModifiers| |------------| |------------------------| |Id | |Id | |Name | |AttributeId | |Description | |SourceId | ------------ |Value | ------------------------ Should I use two separate models (edmx) that transact with a single database containing both deterministic-type and nondeterministic-type tables? Or should/can I use two separate databases in one model? Or two models each with their own database? With distinct models/dbs it seems like this will get really complicated and I'll end up fighting EF a lot, rolling my own transaction code, and generally losing out on a lot of the advantages of the framework. I know these are vague questions, I'm just looking for a sanity check before I forge ahead any further.

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• Inereritance of clousure objects and overriding of methods

  - by bobikk

  I need to extend a class, which is encapsulated in a closure. This base class is following: var PageController = (function(){ // private static variable var _current_view; return function(request, new_view) { ... // priveleged public function, which has access to the _current_view this.execute = function() { alert("PageController::execute"); } } })();` Inheritance is realised using the following function: function extend(subClass, superClass){ var F = function(){ }; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; StartController.cache = ''; if (superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } I subclass the PageController: var StartController = function(request){ // calling the constructor of the super class StartController.superclass.constructor.call(this, request, 'start-view'); } // extending the objects extend(StartController, PageController); // overriding the PageController::execute StartController.prototype.execute = function() { alert('StartController::execute'); } Inheritance is working. I can call every PageController's method from StartController's instance. However, method overriding doesn't work: var startCont = new StartController(); startCont.execute(); alerts "PageController::execute". How should I override this method?

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• Using JAXB to customise the generation of java enums

  - by belltower

  I'm using an external bindings file when using jaxb against an XML schema. I'm mostly using the bindings file to map from the XML schema primitives to my own types. This is a snippet of the bindings file <jxb:bindings version="1.0" xmlns:jxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:ai="http://java.sun.com/xml/ns/jaxb/xjc" extensionBindingPrefixes="ai"> <jxb:bindings schemaLocation="xsdurl" node="xs:schema"> <jxb:globalBindings> <jxb:javaType name="com.companyname.StringType" xmlType="xs:string" parseMethod="parse" printMethod="print" hasNsContext="true"> </jxb:javaType> </jxb:globalBindings> </jxb:bindings> </jxb:bindings> So whenever a xs:string is encountered, the com.companyname.StringType the methods print / parse are called for marshalling/unmarshalling etc. Now if JAXB encounters an xs:enumeration it will generate a java enum. For example: <xs:simpleType name="Address"> <xs:restriction base="xs:string"> <xs:enumeration value="ADDR"/> <xs:enumeration value="PBOX"/> </xs:restriction> </xs:simpleType> public enum Address { ADDR, PBOX, public String value() { return name(); } public static Address fromValue(String v) { return valueOf(v); } } Does anyone know if it is possible to customise the creation of an enum like it is for a primitive? I would like to be able to: Add a standard member variable / other methods to every enum generated by jaxb. Specify the static method used to create the enum.

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• Why can't I run a Perl program from TextMate?

  - by JZ

  I'm following a bioinformatics text, and this represents one of my first Perl scripts. While in TextMate, this does not produce any result. Is it functioning? I added "hello world" at the bottom and I don't see that when I run the script in TextMate. What have I done wrong? #!/usr/local/bin/perl -w use lib "/Users/fogonthedowns/myperllib"; use LWP::Simple; use strict; #Set base URL for all eutils my $utils = "http://eutils.ncbi.nlm.nih.gov/entrez/eutils"; my $db = "Pubmed"; my $query ="Cancer+Prostate"; my $retmax = 10; my $esearch = "$utils/esearch.fcgi?" . "db=$db&retmax=$retmax&term="; my $esearch_result = get($esearch.$query); print "ESEARCH RESULT: $esearch_result\n"; print "Using Query: \n$esearch$query\n"; print "hello world\n";

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• Ruby -- looking for some sort of "Regexp unescape" method

  - by RubyNoobie

  I have a bunch of strings that appear to have been double-escaped -- eg, I have "\\014\"\\000\"\\016smoothing\"\\011mean\"\\022color\"\\011zero@\\016" but I want "\014"\000"\016smoothing"\011mean"\022color"\011zero@\016" Is there a method I can use to unescape them? I imagine that I could make a regex to remove 1 backslash from every consecutive n backslashes, but I don't have a lot of regex experience and it seems there ought to be a "more elegant" way to do it. For example, when I puts MyString it displays the output I'd like, but I don't know how I might capture that into a variable. Thanks! Edited to add context: I have this class that is being used to marshal / restore some stuff, but when I restore some old strings it spits out a type error which I've determined is because they weren't -- for some inexplicable reason -- stored as base64. They instead appear to be 'double-escaped', when I need them to be 'single-escaped' to get restored. require 'base64' class MarshaledStuff < ActiveRecord::Base validates_presence_of :marshaled_obj def contents obj = self.marshaled_obj return Marshal.restore(Base64.decode64(obj)) end def contents=(newcontents) self.marshaled_obj = Base64.encode64(Marshal.dump(newcontents)) end end

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• What's with bad function call in view generated via scaffold?

  - by meta

  I've scaffolded Things element: script/generate scaffold wip/thing name:string and got some invalid function call in views, like: <td><%= link_to 'Edit', edit_thing_path(thing) %></td> Which raise this error: ActionView::TemplateError (undefined method `edit_thing_path' for #<ActionView::Base:0xb5c00944>) on line #11 of app/views/wip/things/index.html.erb: 8: <tr> 9: <td><%=h thing.name %></td> 10: <td><%= link_to 'Show', thing %></td> 11: <td><%= link_to 'Edit', edit_thing_path(thing) %></td> 12: <td><%= link_to 'Destroy', thing, :confirm => 'Are you sure?', :method => :delete %></td> 13: </tr> 14: <% end %> What's with that function? Where is it? Is it some kind of automagic stuff or do I need to implement it (if so - where should it go?) I have resource defined in routes with namespace: map.namespace :wip do |wip| wip.resources :things end rake routes gives me this: wip_things GET /wip/things(.:format) {:action=>"index", :controller=>"wip/things"} POST /wip/things(.:format) {:action=>"create", :controller=>"wip/things"} new_wip_thing GET /wip/things/new(.:format) {:action=>"new", :controller=>"wip/things"} edit_wip_thing GET /wip/things/:id/edit(.:format) {:action=>"edit", :controller=>"wip/things"} wip_thing GET /wip/things/:id(.:format) I assumed that those names (wip_thing, new_wip_thing) are the correct names, but it's still gives me that error Thanks.

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• Django: DatabaseLockError exception with Djapian

  - by jul

  Hi, I've got the exception shown below when executing indexer.update(). I have no idea about what to do: it used to work and now index database seems "locked". Anybody can help? Thanks Environment: Request Method: POST Request URL: http://piem.org:8000/restaurant/add/ Django Version: 1.1.1 Python Version: 2.5.2 Installed Applications: ['django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.comments', 'django.contrib.sites', 'django.contrib.admin', 'registration', 'djapian', 'resto', 'multilingual'] Installed Middleware: ('django.middleware.common.CommonMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', 'django.middleware.locale.LocaleMiddleware', 'multilingual.middleware.DefaultLanguageMiddleware') Traceback: File "/var/lib/python-support/python2.5/django/core/handlers/base.py" in get_response 92. response = callback(request, *callback_args, **callback_kwargs) File "/home/jul/atable/../atable/resto/views.py" in addRestaurant 639. Restaurant.indexer.update() File "/home/jul/python-modules/Djapian-2.3.1-py2.5.egg/djapian/indexer.py" in update 181. database = self._db.open(write=True) File "/home/jul/python-modules/Djapian-2.3.1-py2.5.egg/djapian/database.py" in open 20. xapian.DB_CREATE_OR_OPEN, File "/usr/lib/python2.5/site-packages/xapian.py" in __init__ 2804. _xapian.WritableDatabase_swiginit(self,_xapian.new_WritableDatabase(*args)) Exception Type: DatabaseLockError at /restaurant/add/ Exception Value: Unable to acquire database write lock on /home/jul/atable /djapian_spaces/resto/restaurant/resto.index.restaurantindexer: already locked

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• 1. Get the Current Document Library 2. Create a Folder "MetaFolder" if it's not already present

  - by Rosh Malai

  All I want to do is to create a folder "MetaFolder" inside a document library. User can be on any document library and I would like to create this folder after item is added (so on itemAdded event handler). I do NOT want workflow so please dont suggest workflow. This code works but I have to hardcode the url but need to get url from current url. also need to verify the folder uHippo does not exists in the current doc library... Thanks public override void ItemAdded(SPItemEventProperties properties) { base.ItemAdded(properties); using (SPSite currentSite = new SPSite(properties.WebUrl)) using (SPWeb currentWeb = currentSite.OpenWeb()) { // This code works and creates Folder in the "My TEST Doc library" //SPList docLib = currentWeb.Lists["My TEST Doc Library"]; //SPListItem folder = docLib.Folders.Add(docLib.RootFolder.ServerRelativeUrl, SPFileSystemObjectType.Folder, "My folder"); //folder.Update(); string doclibname = "Not a doclib"; //SPList doclibList = currentWeb.GetList(HttpContext.Current.Request.RawUrl); // NOT WORKING. Tried properties.weburl SPList doclibList = currentWeb.GetListFromUrl("https://mycompanyportal/sites/testsitecol/testwebsite/My%20TEST%20Doc%20Library/Forms/AllItems.aspx"); if (null != doclibList) { doclibname = doclibList.Title; } // this section also not working. // getting Object reference not set to an instance of an object or something like that. //if (currentWeb.GetFolder("uHippo").Exists == false) //{ SPListItem folder = doclibList.Folders.Add(doclibList.RootFolder.ServerRelativeUrl, SPFileSystemObjectType.Folder, "uHippo"); folder.Update(); //} } }

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• Count the no of LI then add class to parent UL.

  - by Wazdesign

  <ul class="taglib-ratings thumbs"> <li id="qezr_yourRating"> <a href="javascript:;" class="rating rate-up "></a> </li> </ul> <ul class="taglib-ratings thumbs"> <li id="qezr_yourRating"> <a href="javascript:;" class="rating rate-up "></a> </li> <li id="qezr_yourRating"> <a href="javascript:;" class="rating rate-up "></a> </li> </ul> I want to apply the class to the UL on base of the Count of the Inner LIs. Like if it has two LI then the class should be like two-thumbs Like if it has one LI then the class should be like one-thumbs I am trying this JS but not working it returns 2 jQuery(document).ready(function(){ var countLi = $(".taglib-ratings > li").size(); alert(countLi); if(countLi == 2) { $(this).parent('.taglib-ratings').addClass('2-col'); alert ('this ul has 2 li'); } else if(countLi == 1) { $(this).parent('.taglib-ratings').addClass('2-col'); alert ('this ul has 1 li'); } else if(countLi > 2) { alert ('this ul has'+ countLi +' li'); } }); Here is the JSbin link to the same. http://jsbin.com/ofeda/edit

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• floating point equality in Python and in general

  - by eric.frederich

  I have a piece of code that behaves differently depending on whether I go through a dictionary to get conversion factors or whether I use them directly. The following piece of code will print 1.0 == 1.0 -> False But if you replace factors[units_from] with 10.0 and factors[units_to ] with 1.0 / 2.54 it will print 1.0 == 1.0 -> True #!/usr/bin/env python base = 'cm' factors = { 'cm' : 1.0, 'mm' : 10.0, 'm' : 0.01, 'km' : 1.0e-5, 'in' : 1.0 / 2.54, 'ft' : 1.0 / 2.54 / 12.0, 'yd' : 1.0 / 2.54 / 12.0 / 3.0, 'mile' : 1.0 / 2.54 / 12.0 / 5280, 'lightyear' : 1.0 / 2.54 / 12.0 / 5280 / 5.87849981e12, } # convert 25.4 mm to inches val = 25.4 units_from = 'mm' units_to = 'in' base_value = val / factors[units_from] ret = base_value * factors[units_to ] print ret, '==', 1.0, '->', ret == 1.0 Let me first say that I am pretty sure what is going on here. I have seen it before in C, just never in Python but since Python in implemented in C we're seeing it. I know that floating point numbers will change values going from a CPU register to cache and back. I know that comparing what should be two equal variables will return false if one of them was paged out while the other stayed resident in a register. Questions What is the best way to avoid problems like this?... In Python or in general. Am I doing something completely wrong? Side Note This is obviously part of a stripped down example but what I'm trying to do is come with with classes of length, volume, etc that can compare against other objects of the same class but with different units. Rhetorical Questions If this is a potentially dangerous problem since it makes programs behave in an undetermanistic matter, should compilers warn or error when they detect that you're checking equality of floats Should compilers support an option to replace all float equality checks with a 'close enough' function? Do compilers already do this and I just can't find the information.

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• How to use a class's type as the type argument for an inherited collection property in C#

  - by Edelweiss Peimann

  I am trying to create a representation of various types of card that inherit from a generic card class and which all contain references to their owning decks. I tried re-declaring them, as suggested here, but it still won't convert to the specific card type. The code I currently have is as such: public class Deck<T> : List<T> where T : Card { void Shuffle() { throw new NotImplementedException("Shuffle not yet implemented."); } } public class Card { public Deck<Card> OwningDeck { get; set; } } public class FooCard : Card { public Deck<FooCard> OwningDeck { get { return (Deck<FooCard>)base.OwningDeck; } set { OwningDeck = value; } } } The compile-time error I am getting: Error 2 Cannot convert type 'Game.Cards.Deck' to 'Game.Cards.Deck' And a warning suggesting I use a new operator to specify that the hiding is intentional. Would doing so be a violation of convention? Is there a better way? My question to stackoverflow is this: Can what I am trying to do be done elegantly in the .NET type system? If so, can some examples be provided?

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• Syncing magento database froms development to production

  - by ringerce

  I use git for version control. I have a development, staging and production environment. When I finish in development I push to staging for review by the client. When approved, I push changes from staging to production. That works fine as long as there is no database changes. What happens if I install modules via Magento connect on local development and it makes database modifications. How would I push those changes up to the production server since the production server is always changing? Edit: I wrote two shell scripts. One that pulls the production database down to my development server, replaces base url with develpment url and updates my development db accordingly. It also leaves the production sql dump behind to be added to my git repo. I'm not really sure if it's beneficial to keep the raw dumps in source control but I'm going to try it out. The second scripts moves the development database up to staging and essentially performs the same operations as the first. Now when it comes time to move to production I pull the updated production repo into the production server and allow magento to do it's thing. I also started using SQLYog recently and it has a database comparison wizard which will give me the differences in my development and production databases and allow me to merge the changes in selectively. It always creates a migration script that I added to source control as well. If anything goes wrong I can run the comparison to see if anything was missed. Does this sounds like a decent workflow to you guys?

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• Trigger ad-hoc activity within a workflow

  - by Chris Taylor

  I am looking to use WF 4 to replace an existing workflow solution we have. One feature that is currently used in the existing workflow engine is the ability to cancel a current activity and loopback to a FlowSwitch type activity. So given the following crude workflow where we start at 'O' and base in the input data the workflow follows the path to 'A2' which is currently blocking on s bookmark waiting for input. ---------A1--\ | \ /\ \ O------- ---->--(A2)-------| ^ \/ / | | | / | | ---------A3--/ | | | |----------------------| However in the meantime some out of band data comes in that means we should cancel 'A2' and return to the FlowSwitch to re-evaluate based on the new data. The question is what is the best way to handle the out of band data that arrived? My initial guess is to have a Parallel activity with one branch waiting for out of band data and the other branch containing the workflow sequence described above. If data came in on the brach waiting for the out of band data, how would I cancel the current activity in the workflow and force it to return to the FlowSwitch. Or of course is there a better way to handle this. I have not actually done any work with the WF4 stuff for WF3 for that matter so I might be missing something obvious here.

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• How to implement an interface class using the non-virtual interface idiom in C++?

  - by andreas buykx

  Hi all, In C++ an interface can be implemented by a class with all its methods pure virtual. Such a class could be part of a library to describe what methods an object should implement to be able to work with other classes in the library: class Lib::IFoo { public: virtual void method() = 0; }; : class Lib::Bar { public: void stuff( Lib::IFoo & ); }; Now I want to to use class Lib::Bar, so I have to implement the IFoo interface. For my purposes I need a whole of related classes so I would like to work with a base class that guarantees common behavior using the NVI idiom: class FooBase : public IFoo // implement interface IFoo { public: void method(); // calls methodImpl; private: virtual void methodImpl(); }; The non-virtual interface (NVI) idiom ought to deny derived classes the possibility of overriding the common behavior implemented in FooBase::method(), but since IFoo made it virtual it seems that all derived classes have the opportunity to override the FooBase::method(). If I want to use the NVI idiom, what are my options other than the pImpl idiom already suggested (thanks space-c0wb0y).

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• Security Exception when using Custom ASP.NET Healthmonitoring event in medium trust

  - by Elementenfresser

  Hi, I'm using custom healthmonitoring events in ASP.NET We recently moved to a new server with default High Trust Permissions. Literature says that healthmonitoring and custom events should work under Medium or higher trust (http://msdn.microsoft.com/en-us/library/bb398933.aspx). Problem is - it doesn't. In less than full trust I get a SecurityException saying The application attempted to perform an operation not allowed by the security policy It works in Full trust or when I remove the inheritance of System.Web.Management.WebErrorEvent. Any suggestions anyone? Here is the super simple code behind with a custom event defined: public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { try { CallCustomEvent(); } catch (Exception ex) { Response.Write(ex.Message); throw ex; } } /// <summary> /// this metho is never called due to lacking permissions... /// </summary> private void CallCustomEvent() { try { //do something useful here } catch (Exception) { //code to instantiate the forbidden inheritance... WebBaseEvent.Raise(new CustomEvent()); } } } /// <summary> /// custom error inheriting WebErrorEvent which is not allowed in high trust? can't believe that... /// </summary> public class CustomEvent : WebErrorEvent { public CustomEvent() : base("test", HttpContext.Current.Request, 100001, new ApplicationException("dummy")) { } } and the Web Config excerpt for high trust: <system.web> <trust level="High" originUrl="" />

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• Dynamic Method Creation

  - by TJMonk15

  So, I have been trying to research this all morning, and have had no luck. I am trying to find a way to dynamically create a method/delegate/lambda that returns a new instance of a certain class (not known until runtime) that inherits from a certain base class. I can guarantee the following about the unknown/dynamic class It will always inherit from one known Class (Row) It will have atleast 2 constructors (one accepting a long, and one accepting an IDataRecord) I plan on doign the following: Finding all classes that have a certain attribute on them Creating a delegate/method/lambda/whatever that creates a new instance of the class Storing the delegate/whatever along with some properties in a struct/class Insert the struct into a hashtable When needed, pull the info out of the hashtable and calling the delegate/whatever to get a new instance of the class and returning it/adding it to a list/etc. I need help only with #2 above!!! I have no idea where to start. I really just need some reference material to get me started, or some keywords to throw into google. This is for a compact/simple to use ORM for our office here. I understand the above is not simple, but once working, should make maintaining the code incredibly simple. Please let me know if you need any more info! And thanks in advance! :)

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• Fluent NHibernate Repository with subclasses

  - by reallyJim

  Having some difficulty understanding the best way to implement subclasses with a generic repository using Fluent NHibernate. I have a base class and two subclasses, say: public abstract class Person { public virtual int PersonId { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } } public class Student : Person { public virtual decimal GPA { get; set; } } public class Teacher : Person { public virtual decimal Salary { get; set; } } My Mappings are as follows: public class PersonMap : ClassMap { public PersonMap() { Table("Persons"); Id(x => x.PersonId).GeneratedBy.Identity(); Map(x => x.FirstName); Map(x => x.LastName); } } public class StudentMap : SubclassMap<Student> { public StudentMap() { Table("Students"); KeyColumn("PersonId"); Map(x => x.GPA); } } public class TeacherMap : SubclassMap<Teacher> { public TeacherMap() { Table("Teachers"); KeyColumn("PersonId"); Map(x => x.Salary); } } I use a generic repository to save/retreive/update the entities, and it works great--provided I'm working with Repository--where I already know that I'm working with students or working with teachers. The problem I run into is this: What happens when I have an ID, and need to determine the TYPE of person? If a user comes to my site as PersonId = 23, how do I go about figuring out which type of person it is?

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• Macro to improve callback registration readability

  - by Warren Seine

  I'm trying to write a macro to make a specific usage of callbacks in C++ easier. All my callbacks are member functions and will take this as first argument and a second one whose type inherits from a common base class. The usual way to go is: register_callback(boost::bind(&my_class::member_function, this, _1)); I'd love to write: register_callback(HANDLER(member_function)); Note that it will always be used within the same class. Even if typeof is considered as a bad practice, it sounds like a pretty solution to the lack of __class__ macro to get the current class name. The following code works: typedef typeof(*this) CLASS; boost::bind(& CLASS :: member_function, this, _1)(my_argument); but I can't use this code in a macro which will be given as argument to register_callback. I've tried: #define HANDLER(FUN) \ boost::bind(& typeof(*this) :: member_function, this, _1); which doesn't work for reasons I don't understand. Quoting GCC documentation: A typeof-construct can be used anywhere a typedef name could be used. My compiler is GCC 4.4, and even if I'd prefer something standard, GCC-specific solutions are accepted.

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