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  • Getting My Head Around Immutability

    - by Michael Mangold
    I'm new to object-oriented programming, and one concept that has been taking me a while to grasp is immutability. I think the light bulb went off last night but I want to verify: When I come across statements that an immutable object cannot be changed, I'm puzzled because I can, for instance, do the following: NSString *myName = @"Bob"; myName = @"Mike"; There, I just changed myName, of immutable type NSString. My problem is that the word, "object" can refer to the physical object in memory, or the abstraction, "myName." The former definition applies to the concept of immutability. As for the variable, a more clear (to me) definition of immutability is that the value of an immutable object can only be changed by also changing its location in memory, i.e. its reference (also known as its pointer). Is this correct, or am I still lost in the woods?

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  • Is it good practice to use functions just to centralize common code?

    - by EpsilonVector
    I run across this problem a lot. For example, I currently write a read function and a write function, and they both check if buf is a NULL pointer and that the mode variable is within certain boundaries. This is code duplication. This can be solved by moving it into its own function. But should I? This will be a pretty anemic function (doesn't do much), rather localized (so not general purpose), and doesn't stand well on its own (can't figure out what you need it for unless you see where it is used). Another option is to use a macro, but I want to talk about functions in this post. So, should you use a function for something like this? What are the pros and cons?

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  • VS2010 crashes when opening a vsp generated using VS 2012

    - by Tarun Arora
    I recently profiled some web applications using Visual Studio 2012, a vsp (Visual Studio Profile) file was generated as a result of the profiling session. I could successfully open the vsp file in Visual Studio 2012 as expected but when I tried to open the vsp file in Visual Studio 2010 the VS2010 IDE crashed. As a responsible citizen I raised bug # 762202 on Microsoft Connect site using the Microsoft Visual Studio 2012 Feedback Client. Note – In case you didn’t already know, VSP generated in Visual Studio 2012 is not backward compatible. Please refer below for the steps to reproduce the issue and the resolution of the connect bug. 1. Behaviour and Steps to Reproduce the Issue Description I have generated a vsp file by using the Visual Studio 2012 Standalone profiler. When I try and open the vsp file in Visual Studio 2010 the IDE crashes. I understand that a vsp generated by using VS 2012 cannot be opened in VS 2010, but the IDE crashing is not the behaviour I would expect to see. Steps to Reproduce the Issue 1. Pick up the Stand lone profiler from the VS 2012 installation media. The folder has both x 64 and x86 installer, since the machine I am using is x64 bit. I have installed the x64 version of the standalone profiler. 2. I have configured the system path by setting the 'environment variable' path to where the profiler is installed. In my case this is, C:\Program Files (x86)\Microsoft Visual Studio 11.0\Team Tools\Performance Tools 3. Created a new environment variable _NT_SYMBOL_PATH and set its value to CACHE*C:\SYMBOLSCACHE;SRV*C:\SYMBOLSCACHE*HTTP://MSDL.MICROSOFT.COM/DOWNLOAD/SYMBOLS;\\FOO\BUILD1234 4. Open up CMD as an administrator and run 'VSPerfASPNETCmd /tip http://localhost:56180/ /o:C:\Temp\SampleEISK.vsp' 5. This generates the following message on the cmd       Microsoft (R) VSPerf ASP.NET Command, Version 11.0.0.0     Copyright (C) Microsoft Corporation. All rights reserved.     Configuring and attaching to ASP.NET process. Please wait.     Setting up profiling environment.     Starting monitor.     Launching ASP.NET service.     Attaching Monitor to process.     Launching Internet Explorer.     The profiler is attached to ASP.net. Please run your application scenario now.     Press Enter to stop data collection...   6. I perform certain actions and then I come back to the cmd and hit enter to shut down the profiling. Once I do this, the following message is written to the cmd, Press Enter to stop data collection... Profiling now shut down. Report file "C:\Temp\SampleEISK.vsp" was generated. Running VsPerfReport, packing symbols into the .VSP. Shutting down profiling and restarting ASP.NET. Please wait. Restarting w3wp.exe.   7. I look in the C:\Temp folder and I can see the SampleEISK.vsp file generated. I can successfully open this file in Visual Studio 2012. 8. When I am trying to open the vsp file in VS 2010 the VS 2010 IDE crashes. Kaboooom! What I would expect to happen I expect to receive a message "VS 2010 does not support the vsp file generated by VS 2012". What actually happened The VS 2010 IDE crashed 2. Resolution This is a valid bug! However, there isn’t much value in releasing a hotfix for this issue. Refer below to the resolution provided by the Visual Studio Profiler Team.  Thank you for taking the time to report this issue. We completely agree that Visual Studio 2010 should not crash. However in this particular case this is not a bug we are going to retroactively release a fix to 2010 for at this point. Given that a fix would not unblock the scenario of opening a 2012 created file on Visual Studio 2010, and there is not an active update channel for Visual Studio 2010 other than manually locating and installing hot fixes, we will not be fixing this particular issue. Best Regards, Visual Studio Profiler Team   Though it would be great to improve the behaviour however, this is not a defect that would stop you from progressing in any way. It’s important to note however that VSP files generated by Visual Studio 2012 are not backward compatible so you should refrain from opening these files in Visual Studio 2010.

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  • Namespaces are obsolete

    - by Bertrand Le Roy
    To those of us who have been around for a while, namespaces have been part of the landscape. One could even say that they have been defining the large-scale features of the landscape in question. However, something happened fairly recently that I think makes this venerable structure obsolete. Before I explain this development and why it’s a superior concept to namespaces, let me recapitulate what namespaces are and why they’ve been so good to us over the years… Namespaces are used for a few different things: Scope: a namespace delimits the portion of code where a name (for a class, sub-namespace, etc.) has the specified meaning. Namespaces are usually the highest-level scoping structures in a software package. Collision prevention: name collisions are a universal problem. Some systems, such as jQuery, wave it away, but the problem remains. Namespaces provide a reasonable approach to global uniqueness (and in some implementations such as XML, enforce it). In .NET, there are ways to relocate a namespace to avoid those rare collision cases. Hierarchy: programmers like neat little boxes, and especially boxes within boxes within boxes. For some reason. Regular human beings on the other hand, tend to think linearly, which is why the Windows explorer for example has tried in a few different ways to flatten the file system hierarchy for the user. 1 is clearly useful because we need to protect our code from bleeding effects from the rest of the application (and vice versa). A language with only global constructs may be what some of us started programming on, but it’s not desirable in any way today. 2 may not be always reasonably worth the trouble (jQuery is doing fine with its global plug-in namespace), but we still need it in many cases. One should note however that globally unique names are not the only possible implementation. In fact, they are a rather extreme solution. What we really care about is collision prevention within our application. What happens outside is irrelevant. 3 is, more than anything, an aesthetical choice. A common convention has been to encode the whole pedigree of the code into the namespace. Come to think about it, we never think we need to import “Microsoft.SqlServer.Management.Smo.Agent” and that would be very hard to remember. What we want to do is bring nHibernate into our app. And this is precisely what you’ll do with modern package managers and module loaders. I want to take the specific example of RequireJS, which is commonly used with Node. Here is how you import a module with RequireJS: var http = require("http"); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This is of course importing a HTTP stack module into the code. There is no noise here. Let’s break this down. Scope (1) is provided by the one scoping mechanism in JavaScript: the closure surrounding the module’s code. Whatever scoping mechanism is provided by the language would be fine here. Collision prevention (2) is very elegantly handled. Whereas relocating is an afterthought, and an exceptional measure with namespaces, it is here on the frontline. You always relocate, using an extremely familiar pattern: variable assignment. We are very much used to managing our local variable names and any possible collision will get solved very easily by picking a different name. Wait a minute, I hear some of you say. This is only taking care of collisions on the client-side, on the left of that assignment. What if I have two libraries with the name “http”? Well, You can better qualify the path to the module, which is what the require parameter really is. As for hierarchical organization, you don’t really want that, do you? RequireJS’ module pattern does elegantly cover the bases that namespaces used to cover, but it also promotes additional good practices. First, it promotes usage of self-contained, single responsibility units of code through the closure-based, stricter scoping mechanism. Namespaces are somewhat more porous, as using/import statements can be used bi-directionally, which leads us to my second point… Sane dependency graphs are easier to achieve and sustain with such a structure. With namespaces, it is easy to construct dependency cycles (that’s bad, mmkay?). With this pattern, the equivalent would be to build mega-components, which are an easier problem to spot than a decay into inter-dependent namespaces, for which you need specialized tools. I really like this pattern very much, and I would like to see more environments implement it. One could argue that dependency injection has some commonalities with this for example. What do you think? This is the half-baked result of some morning shower reflections, and I’d love to read your thoughts about it. What am I missing?

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  • MacBook Pro (5) touchpad stops working after upgrading from Ubuntu 10.10 to Ubuntu 11.04

    - by Rob
    After upgrading from Ubuntu 10.10 to Ubuntu 11.04, my MacBook Pro's touchpad stopped working. It works fine on the login screen, but after logging in it stops working. (Answering my own question, in the hope that it saves someone else a bit of head scratching. I'm a new user, so couldn't answer in a separate post for the next few hours). After the upgrade, your Gnome desktop configuration may have gone awry. There are a few settings which enable or disable the touchpad in certain contexts which may need tweaking to get the touchpad working again. Here's how I got mine working again: Hit Alt-F2, and run 'gconf-editor' Navigate to desktop-gnome-peripherals Ensure that peripherals-touchpad:touchpad is enabled. Ensure that peripherals-bcm5974:disable_while_other_device_exists is disabled. 'bcm5974' is probably specific to my MacBook Pro's hardware, so you may need to search around for variable disable_while_other_device_exists under the entries listed under peripherals. HTH

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  • jqGrid - dynamically load different drop down values for different rows depending on another column value

    - by Renso
    Goal: As we all know the jqGrid examples in the demo and the Wiki always refer to static values for drop down boxes. This of course is a personal preference but in dynamic design these values should be populated from the database/xml file, etc, ideally JSON formatted. Can you do this in jqGrid, yes, but with some custom coding which we will briefly show below (refer to some of my other blog entries for a more detailed discussion on this topic). What you CANNOT do in jqGrid, referrign here up and to version 3.8.x, is to load different drop down values for different rows in the jqGrid. Well, not without some trickery, which is what this discussion is about. Issue: Of course the issue is that jqGrid has been designed for high performance and thus I have no issue with them loading a  reference to a single drop down values list for every column. This way if you have 500 rows or one, each row only refers to a single list for that particuolar column. Nice! SO how easy would it be to simply traverse the grid once loaded on gridComplete or loadComplete and simply load the select tag's options from scratch, via ajax, from memory variable, hard coded etc? Impossible! Since their is no embedded SELECT tag within each cell containing the drop down values (remeber it only has a reference to that list in memory), all you will see when you inspect the cell prior to clicking on it, or even before and on beforeEditCell, is an empty <TD></TD>. When trying to load that list via a click event on that cell will temporarily load the list but jqGrid's last internal callback event will remove it and replace it with the old one, and you are back to square one. Solution: Yes, after spending a few hours on this found a solution to the problem that does not require any updates to jqGrid source code, thank GOD! Before we get into the coding details, the solution here can of course be customized to suite your specific needs, this one loads the entire drop down list that would be needed across all rows once into global variable. I then parse this object that contains all the properties I need to filter the rows depending on which ones I want the user to see based off of another cell value in that row. This only happens when clicking the cell, so no performance penalty. You may of course to load it via ajax when the user clicks the cell, but I found it more effecient to load the entire list as part of jqGrid's normal editoptions: { multiple: false, value: listingStatus } colModel options which again keeps only a reference to the sinlge list, no duplciation. Lets get into the meat and potatoes of it.         var acctId = $('#Id').val();         var data = $.ajax({ url: $('#ajaxGetAllMaterialsTrackingLookupDataUrl').val(), data: { accountId: acctId }, dataType: 'json', async: false, success: function(data, result) { if (!result) alert('Failure to retrieve the Alert related lookup data.'); } }).responseText;         var lookupData = eval('(' + data + ')');         var listingCategory = lookupData.ListingCategory;         var listingStatus = lookupData.ListingStatus;         var catList = '{';         $(lookupData.ListingCategory).each(function() {             catList += this.Id + ':"' + this.Name + '",';         });         catList += '}';         var lastsel;         var ignoreAlert = true;         $(item)         .jqGrid({             url: listURL,             postData: '',             datatype: "local",             colNames: ['Id', 'Name', 'Commission<br />Rep', 'Business<br />Group', 'Order<br />Date', 'Edit', 'TBD', 'Month', 'Year', 'Week', 'Product', 'Product<br />Type', 'Online/<br />Magazine', 'Materials', 'Special<br />Placement', 'Logo', 'Image', 'Text', 'Contact<br />Info', 'Everthing<br />In', 'Category', 'Status'],             colModel: [                 { name: 'Id', index: 'Id', hidden: true, hidedlg: true },                 { name: 'AccountName', index: 'AccountName', align: "left", resizable: true, search: true, width: 100 },                 { name: 'OnlineName', index: 'OnlineName', align: 'left', sortable: false, width: 80 },                 { name: 'ListingCategoryName', index: 'ListingCategoryName', width: 85, editable: true, hidden: false, edittype: "select", editoptions: { multiple: false, value: eval('(' + catList + ')') }, editrules: { required: false }, formatoptions: { disabled: false} }             ],             jsonReader: {                 root: "List",                 page: "CurrentPage",                 total: "TotalPages",                 records: "TotalRecords",                 userdata: "Errors",                 repeatitems: false,                 id: "0"             },             rowNum: $rows,             rowList: [10, 20, 50, 200, 500, 1000, 2000],             imgpath: jQueryImageRoot,             pager: $(item + 'Pager'),             shrinkToFit: true,             width: 1455,             recordtext: 'Traffic lines',             sortname: 'OrderDate',             viewrecords: true,             sortorder: "asc",             altRows: true,             cellEdit: true,             cellsubmit: "remote",             cellurl: editURL + '?rows=' + $rows + '&page=1',             loadComplete: function() {               },             gridComplete: function() {             },             loadError: function(xhr, st, err) {             },             afterEditCell: function(rowid, cellname, value, iRow, iCol) {                 var select = $(item).find('td.edit-cell select');                 $(item).find('td.edit-cell select option').each(function() {                     var option = $(this);                     var optionId = $(this).val();                     $(lookupData.ListingCategory).each(function() {                         if (this.Id == optionId) {                                                       if (this.OnlineName != $(item).getCell(rowid, 'OnlineName')) {                                 option.remove();                                 return false;                             }                         }                     });                 });             },             search: true,             searchdata: {},             caption: "List of all Traffic lines",             editurl: editURL + '?rows=' + $rows + '&page=1',             hiddengrid: hideGrid   Here is the JSON data returned via the ajax call during the jqGrid function call above (NOTE it must be { async: false}: {"ListingCategory":[{"Id":29,"Name":"Document Imaging & Management","OnlineName":"RF Globalnet"} ,{"Id":1,"Name":"Ancillary Department Hardware","OnlineName":"Healthcare Technology Online"} ,{"Id":2,"Name":"Asset Tracking","OnlineName":"Healthcare Technology Online"} ,{"Id":3,"Name":"Asset Tracking","OnlineName":"Healthcare Technology Online"} ,{"Id":4,"Name":"Asset Tracking","OnlineName":"Healthcare Technology Online"} ,{"Id":5,"Name":"Document Imaging & Management","OnlineName":"Healthcare Technology Online"} ,{"Id":6,"Name":"Document Imaging & Management","OnlineName":"Healthcare Technology Online"} ,{"Id":7,"Name":"EMR/EHR Software","OnlineName":"Healthcare Technology Online"}]} I only need the Id and Name for the drop down list, but the third column in the JSON object is important, it is the only that I match up with the OnlineName in the jqGrid column, and then in the loop during afterEditCell simply remove the ones I don't want the user to see. That's it!

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  • GTK applications do not start

    - by Greg
    Hello, I have a fresh install of Ubuntu 10.04 Server on nodes of a computational cluster, and I access the nodes via ssh. I configured a X server, which I start with the command startx -- -ac. The server is running fine on port :0. Then, I set the environment variable DISPLAY to :0. Now, when I run a GTK application on the node, it fails with the following error: Error: Unable to initialize gtk, is DISPLAY set properly? Now, my question is, is there any runtime library that I need for running GTK applications on top of a X server? I'm probably missing something obvious here, but I can't tell what :P

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  • Creating a curved mesh on inside of sphere based on texture image coordinates

    - by user5025
    In Blender, I have created a sphere with a panoramic texture on the inside. I have also manually created a plane mesh (curved to match the size of the sphere) that sits on the inside wall where I can draw a different texture. This is great, but I really want to reduce the manual labor, and do some of this work in a script -- like having a variable for the panoramic image, and coordinates of the area in the photograph that I want to replace with a new mesh. The hardest part of doing this is going to be creating a curved mesh in code that can sit on the inside wall of a sphere. Can anyone point me in the right direction?

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  • Two new features in November 2009 CTP

    - by kaleidoscope
    Windows Azure Diagnostics Managed Library: The new Diagnostics API enables logging using standard .NET APIs. The Diagnostics API provides built-in support for collecting standard logs and diagnostic information, including the Windows Azure logs, IIS 7.0 logs, Failed Request logs, crash dumps, Windows Event logs, performance counters, and custom logs. Variable-size Virtual Machines (VMs): Developers may now specify the size of the virtual machine to which they wish to deploy a role instance, based on the role's resource requirements. The size of the VM determines the number of CPU cores, the memory capacity, and the local file system size allocated to a running instance. e.g.: <WebRole name=”WebRole1” vmsize=”ExtraLarge”> Supported values for the ‘vmsize’ are: 1. Small 2. Medium 3. Large 4.       ExtraLarge More information for Diagnostics Managed Library can be found at: http://msdn.microsoft.com/en-us/library/ee758705.aspx   Girish, A

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  • Why do some opensouce libraries lack comments?

    - by entropy
    I don't know if this happens to most Opensource libraries, but many of I know and use (for example OpenSSL, Webkit, ...) they all lack comments, or contain very few comments. Not to mention their very few documents, it is hard to read their source code. We can hardly understand what a member variable means, or what this function does. This seems to be against coding standard practice Why is that? How can people collaborate to these opensource with very few comments?

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  • Is it possible to get a Proxy Authentication Dialog with Ubuntu Server?

    - by Johnny Bigoode
    I've got a VM Virtual Box with Ubuntu Server. I'set the http_proxy variable using export http_proxy="http://1234:linux@proxy:8080" The problem is that Ubuntu will constantly try to connect to the internet, even when I'm not logged in my company's account, so everyday I need to reset my password since Ubuntu will constantly try to access the internet. Also, it's always a problem when I need to authenticate the proxy with a different user/password. Can't I just set it to make a small prompt when it tries to connect to the proxy and fails? Like Firefox, Chrome and every app I have installed with Windows 7? I get this small dialog box that asks for a username and password when it can't access the internet. The Ubuntu Server doesn't need constant internet connection, specially since it's only online for tests over LAN.

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  • Level and Player objects - which should contain which?

    - by Thane Brimhall
    I've been working on a several simple games, and I've always come to a decision point where I have to choose whether to have the Level object as an attribute of the Player class or the Player as an attribute of the Level class. I can see arguments for both: The Level should contain the player because it also contains every other entity. In fact it just makes sense this way: "John is in the room." It makes it a bit more difficult to move the player to a new level, however, because then each level has to pass its player object to an upcoming level. On the other hand, it makes programming sense to me to leave the player as the top-level object that is persistent between levels, and the environment changes because the player decides to change his level and location. It becomes very easy to change levels, because all I have to do is replace the level variable on the player. What's the most common practice here? Or better yet, is there a "right" way to architecture this relationship?

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  • What are the basic skills a beginner JavaScript programmer should have?

    - by Sanford
    In NYC, we are working on creating a collaborative community programming environment and trying to segment out software engineers into differing buckets. At present, we are trying to define: Beginners Intermediates Advanced Experts (and/or Masters) Similar to an apprenticeship, you would need to demonstrate specific skills to achieve different levels. Right now, we have identified beginner programming skills as: Object - method, attributes, inheritance Variable - math, string, array, boolean - all are objects Basic arithmetic functions - precedence of functions String manipulation Looping - flow control Conditionals - boolean algebra This is a first attempt, and it is a challenge since we know the natural tension between programming and software engineering. How would you create such a skills-based ranking for JavaScript in this manner? For example, what would be the beginner JavaScript skills that you would need to have to advance to the intermediate training? And so on.

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  • What approaches can I take to lower the odds of introducing new bugs in a complex legacy app?

    - by m.edmondson
    Where I work I often have to develop (and bug fix) in an old system (.NET 1) whos code is complete spaghetti - with little thought given to variable names, program structure nor comments. Because of this it takes me ages to understand what bits need changed, and I often 'break' the existing software because I've made a modification. I really really want to spend a couple of months (with colleagues) going through it to refactor but existing developers both can't see the need - nor think theres time for this (the system is massive). I dread having to work on its code as it takes days to fix something only to find out I've broken something else. This obviously makes me look incompetent - so how can I deal with this?

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  • Habanero

    - by csharp-source.net
    An Enterprise Application Framework for .Net that is ideally suited for developing applications in an agile manner. The framework is used for producing an application from the data layer through to the front-end. Free open source under the LGPL license, it includes ORM, code generation and runtime UI generation to create one application for the desktop & web. Features: * ORM: Map database tables to objects in code * Persist property values to and from the database * Define all mapping in a single XML file * Switch between database vendors with one setting * Support for MySQL, MS Sql Server, MS Access, Oracle, PostgreSQL, SQLite, Firebird * FireStarter GUI class definitions xml manager * Generate user interfaces and map properties to controls * Develop for both desktop (with Windows Forms) and web (with Gizmox' Visual WebGUI) * Generate new projects and code files * Generate UI forms from templates * Reverse engineer class definitions from existing databases * Support variable data sources, including an in-memory database. Ships with Firestarter a free database reverse engineering, Domain Modelling and Code Generator.

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  • Null Values And The T-SQL IN Operator

    - by Jesse
    I came across some unexpected behavior while troubleshooting a failing test the other day that took me long enough to figure out that I thought it was worth sharing here. I finally traced the failing test back to a SELECT statement in a stored procedure that was using the IN t-sql operator to exclude a certain set of values. Here’s a very simple example table to illustrate the issue: Customers CustomerId INT, NOT NULL, Primary Key CustomerName nvarchar(100) NOT NULL SalesRegionId INT NULL   The ‘SalesRegionId’ column contains a number representing the sales region that the customer belongs to. This column is nullable because new customers get created all the time but assigning them to sales regions is a process that is handled by a regional manager on a periodic basis. For the purposes of this example, the Customers table currently has the following rows: CustomerId CustomerName SalesRegionId 1 Customer A 1 2 Customer B NULL 3 Customer C 4 4 Customer D 2 5 Customer E 3   How could we write a query against this table for all customers that are NOT in sales regions 2 or 4? You might try something like this: 1: SELECT 2: CustomerId, 3: CustomerName, 4: SalesRegionId 5: FROM Customers 6: WHERE SalesRegionId NOT IN (2,4)   Will this work? In short, no; at least not in the way that you might expect. Here’s what this query will return given the example data we’re working with: CustomerId CustomerName SalesRegionId 1 Customer A 1 5 Customer E 5   I was expecting that this query would also return ‘Customer B’, since that customer has a NULL SalesRegionId. In my mind, having a customer with no sales region should be included in a set of customers that are not in sales regions 2 or 4.When I first started troubleshooting my issue I made note of the fact that this query should probably be re-written without the NOT IN clause, but I didn’t suspect that the NOT IN clause was actually the source of the issue. This particular query was only one minor piece in a much larger process that was being exercised via an automated integration test and I simply made a poor assumption that the NOT IN would work the way that I thought it should. So why doesn’t this work the way that I thought it should? From the MSDN documentation on the t-sql IN operator: If the value of test_expression is equal to any value returned by subquery or is equal to any expression from the comma-separated list, the result value is TRUE; otherwise, the result value is FALSE. Using NOT IN negates the subquery value or expression. The key phrase out of that quote is, “… is equal to any expression from the comma-separated list…”. The NULL SalesRegionId isn’t included in the NOT IN because of how NULL values are handled in equality comparisons. From the MSDN documentation on ANSI_NULLS: The SQL-92 standard requires that an equals (=) or not equal to (<>) comparison against a null value evaluates to FALSE. When SET ANSI_NULLS is ON, a SELECT statement using WHERE column_name = NULL returns zero rows even if there are null values in column_name. A SELECT statement using WHERE column_name <> NULL returns zero rows even if there are nonnull values in column_name. In fact, the MSDN documentation on the IN operator includes the following blurb about using NULL values in IN sub-queries or expressions that are used with the IN operator: Any null values returned by subquery or expression that are compared to test_expression using IN or NOT IN return UNKNOWN. Using null values in together with IN or NOT IN can produce unexpected results. If I were to include a ‘SET ANSI_NULLS OFF’ command right above my SELECT statement I would get ‘Customer B’ returned in the results, but that’s definitely not the right way to deal with this. We could re-write the query to explicitly include the NULL value in the WHERE clause: 1: SELECT 2: CustomerId, 3: CustomerName, 4: SalesRegionId 5: FROM Customers 6: WHERE (SalesRegionId NOT IN (2,4) OR SalesRegionId IS NULL)   This query works and properly includes ‘Customer B’ in the results, but I ultimately opted to re-write the query using a LEFT OUTER JOIN against a table variable containing all of the values that I wanted to exclude because, in my case, there could potentially be several hundred values to be excluded. If we were to apply the same refactoring to our simple sales region example we’d end up with: 1: DECLARE @regionsToIgnore TABLE (IgnoredRegionId INT) 2: INSERT @regionsToIgnore values (2),(4) 3:  4: SELECT 5: c.CustomerId, 6: c.CustomerName, 7: c.SalesRegionId 8: FROM Customers c 9: LEFT OUTER JOIN @regionsToIgnore r ON r.IgnoredRegionId = c.SalesRegionId 10: WHERE r.IgnoredRegionId IS NULL By performing a LEFT OUTER JOIN from Customers to the @regionsToIgnore table variable we can simply exclude any rows where the IgnoredRegionId is null, as those represent customers that DO NOT appear in the ignored regions list. This approach will likely perform better if the number of sales regions to ignore gets very large and it also will correctly include any customers that do not yet have a sales region.

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  • Subterranean IL: The ThreadLocal type

    - by Simon Cooper
    I came across ThreadLocal<T> while I was researching ConcurrentBag. To look at it, it doesn't really make much sense. What's all those extra Cn classes doing in there? Why is there a GenericHolder<T,U,V,W> class? What's going on? However, digging deeper, it's a rather ingenious solution to a tricky problem. Thread statics Declaring that a variable is thread static, that is, values assigned and read from the field is specific to the thread doing the reading, is quite easy in .NET: [ThreadStatic] private static string s_ThreadStaticField; ThreadStaticAttribute is not a pseudo-custom attribute; it is compiled as a normal attribute, but the CLR has in-built magic, activated by that attribute, to redirect accesses to the field based on the executing thread's identity. TheadStaticAttribute provides a simple solution when you want to use a single field as thread-static. What if you want to create an arbitary number of thread static variables at runtime? Thread-static fields can only be declared, and are fixed, at compile time. Prior to .NET 4, you only had one solution - thread local data slots. This is a lesser-known function of Thread that has existed since .NET 1.1: LocalDataStoreSlot threadSlot = Thread.AllocateNamedDataSlot("slot1"); string value = "foo"; Thread.SetData(threadSlot, value); string gettedValue = (string)Thread.GetData(threadSlot); Each instance of LocalStoreDataSlot mediates access to a single slot, and each slot acts like a separate thread-static field. As you can see, using thread data slots is quite cumbersome. You need to keep track of LocalDataStoreSlot objects, it's not obvious how instances of LocalDataStoreSlot correspond to individual thread-static variables, and it's not type safe. It's also relatively slow and complicated; the internal implementation consists of a whole series of classes hanging off a single thread-static field in Thread itself, using various arrays, lists, and locks for synchronization. ThreadLocal<T> is far simpler and easier to use. ThreadLocal ThreadLocal provides an abstraction around thread-static fields that allows it to be used just like any other class; it can be used as a replacement for a thread-static field, it can be used in a List<ThreadLocal<T>>, you can create as many as you need at runtime. So what does it do? It can't just have an instance-specific thread-static field, because thread-static fields have to be declared as static, and so shared between all instances of the declaring type. There's something else going on here. The values stored in instances of ThreadLocal<T> are stored in instantiations of the GenericHolder<T,U,V,W> class, which contains a single ThreadStatic field (s_value) to store the actual value. This class is then instantiated with various combinations of the Cn types for generic arguments. In .NET, each separate instantiation of a generic type has its own static state. For example, GenericHolder<int,C0,C1,C2> has a completely separate s_value field to GenericHolder<int,C1,C14,C1>. This feature is (ab)used by ThreadLocal to emulate instance thread-static fields. Every time an instance of ThreadLocal is constructed, it is assigned a unique number from the static s_currentTypeId field using Interlocked.Increment, in the FindNextTypeIndex method. The hexadecimal representation of that number then defines the specific Cn types that instantiates the GenericHolder class. That instantiation is therefore 'owned' by that instance of ThreadLocal. This gives each instance of ThreadLocal its own ThreadStatic field through a specific unique instantiation of the GenericHolder class. Although GenericHolder has four type variables, the first one is always instantiated to the type stored in the ThreadLocal<T>. This gives three free type variables, each of which can be instantiated to one of 16 types (C0 to C15). This puts an upper limit of 4096 (163) on the number of ThreadLocal<T> instances that can be created for each value of T. That is, there can be a maximum of 4096 instances of ThreadLocal<string>, and separately a maximum of 4096 instances of ThreadLocal<object>, etc. However, there is an upper limit of 16384 enforced on the total number of ThreadLocal instances in the AppDomain. This is to stop too much memory being used by thousands of instantiations of GenericHolder<T,U,V,W>, as once a type is loaded into an AppDomain it cannot be unloaded, and will continue to sit there taking up memory until the AppDomain is unloaded. The total number of ThreadLocal instances created is tracked by the ThreadLocalGlobalCounter class. So what happens when either limit is reached? Firstly, to try and stop this limit being reached, it recycles GenericHolder type indexes of ThreadLocal instances that get disposed using the s_availableIndices concurrent stack. This allows GenericHolder instantiations of disposed ThreadLocal instances to be re-used. But if there aren't any available instantiations, then ThreadLocal falls back on a standard thread local slot using TLSHolder. This makes it very important to dispose of your ThreadLocal instances if you'll be using lots of them, so the type instantiations can be recycled. The previous way of creating arbitary thread-static variables, thread data slots, was slow, clunky, and hard to use. In comparison, ThreadLocal can be used just like any other type, and each instance appears from the outside to be a non-static thread-static variable. It does this by using the CLR type system to assign each instance of ThreadLocal its own instantiated type containing a thread-static field, and so delegating a lot of the bookkeeping that thread data slots had to do to the CLR type system itself! That's a very clever use of the CLR type system.

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  • What does this snippet work? It uses session cookie [closed]

    - by Emerald214
    My website is a gadget application. It uses CakePHP framework. It has the below snippet in AppController. I searched the cookie variable in the project but can't find any other occurences. I also don't understand what it works. Why does it always check this in every request. if ( isset( $_COOKIE[session_name()] ) ) { if ( !isset( $this->sns_id ) ) { // ????????? $this->cakeError( 'session' ); } } else { // ?????????????????? if ( !isset( $_REQUEST['post_pf_params'] ) ) { $this->cakeError( 'cookie' ); } }

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  • Jquery Carousel - Need A Script Hack to Customize

    - by Leah
    I hope someone can help me out here. I am coding a site for a client using the carouFredsel. I am using this because it allows for variable widths with in the slideshow as seen here: http://2938.sandbox.i3dthemes.net/index-old.html. My problems are as follows: to use the built in auto center script the scrolling changes the white space in between images during the transition to fit the width of the wrapper. I need a hack to keep the white space during transition the same, like this: http://2938.sandbox.i3dthemes.net/index.html. Also, I can't figure out how to put this snippet into my code and make it work scroll: { onAfter: function() { if ( $(this).triggerHandler( "currentPosition" ) == 0 ) { $(this).trigger( "pause" ); } } }

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  • Javascript naming conventions

    - by ManuPK
    I am from Java background and am new to JavaScript. I have noticed many JavaScript methods using single character parameter names, such as in the following example. doSomething(a,b,c) I don't like it, but a fellow JavaScript developer convinced me that this is done to reduce the file size, noting that JavaScript files have to be transferred to the browser. Then I found myself talking to another developer. He showed me the way that Firefox will truncate variable names to load the page faster. Is this a standard practice for web browsers? What are the best-practice naming conversions that should be followed when programming in JavaScript? Does identifier length matter, and if so, to what extent?

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  • OOP private method parameters coding style

    - by Jake
    After coding for many years as a solo programmer, I have come to feel that most of the time there are many benefits to write private member functions with all of the used member variables included in the parameter list, especially development stage. This allow me to check at one look what member variables are used and also allow me to supply other values for tests and debugging. Also, a change in code by removing a particular member variable can break many functions. In this case however, the private function remains isolated am I can still call it using other values without fixing the function. Is this a bad idea afterall, especially in a team environment? Is it like redundant or confusing, or are there better ways?

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  • Using RegEx's in Multi-Channel Funnels in Google Analytics

    - by Rob H
    For some reason, I can't get my multi-channel funnel which utilizes RegEx's in the path steps to function -- it keeps coming back with no data. There are a few variables which may be holding things up, but I can't figure out the origin of the problem, nor a solution. Here's the situation: The funnel is tracking conversions, defined as when a user completes 4 steps to signup Steps are not "required" Default URL is set to https://example.com There is a 302 redirect set up on our site that leads from http://example.com to https://example.com Within the funnel, steps switch from non-secure pages (unless browser is set to secure browsing), to secure pages once the user moves from the landing page to the second page of the sign-up process (account placeholder has been created) URL at that point contains the variable of publisher number within (but not at the end) the URL My RegEx's are all properly written as tested on rubular.com

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  • How to make custom libraries accessible?

    - by Milen Bilyanov
    I am trying to compile and install every custom module under it's own designated folder. (ex: /myApps/myLinux/compiled_app) I had luck with python so far, where my python is compiled from source and lives in: /myApps/myLinux/python2.5 and "python2.5" - /myApps/myLinux/python2.5.6-gcc463 so I can access this python through a wrapper script that sets the right environment. The question is recently I had to compile and add something called gperf3.0.4. So now it lives: /myApps/myLinux/gperf3.0 and "gperf3.0" - /myApps/myLinux/gperf3.0.4-gcc463 The question is: How will I point to this lib if some other app needs to access it? Is it done through the LD_LIBRARY_PATH variable? Thanks.

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  • Unable to Call Instantiate in Class Member Function

    - by onguarde
    The following javascript is attached to a gameObject. var instance : GameObject; class eg_class { function eg_func(){ var thePrefab : GameObject; instance = Instantiate(thePrefab); } } Error, Unknown identifier: 'instance'. Unknown identifier: 'Instantiate'. Questions, 1) Why is it that "instance" cannot be accessed within a class? Isn't it supposed to be a public variable? 2) "Instantiate" function works in Start()/Update() root functions. Is there a way to make it work from within member functions? Thanks in advance!

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  • What do you do when your naming convention clashes with your language?

    - by Jon Purdy
    Okay, this is one of those little things that always bugged me. I typically don't abbreviate identifiers, and the only time I use a short identifier (e.g., i) is for a tight loop. So it irritates me when I'm working in C++ and I have a variable that needs to be named operator or class and I have to work around it or use an abbreviation, because it ends up sticking out. Caveat: this may happen to me disproportionately often because I work a lot in programming language design, where domain objects may mirror concepts in the host language and inadvertently cause clashes. How would you deal with this? Abbreviate? (op) Misspell? (klass) Something else? (operator_)

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