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  • What does it mean that "Lisp can be written in itself?"

    - by Mason Wheeler
    Paul Graham wrote that "The unusual thing about Lisp-- in fact, the defining quality of Lisp-- is that it can be written in itself." But that doesn't seem the least bit unusual or definitive to me. ISTM that a programming language is defined by two things: Its compiler or interpreter, which defines the syntax and the semantics for the language by fiat, and its standard library, which defines to a large degree the idioms and techniques that skilled users will use when writing code in the language. With a few specific exceptions, (the non-C# members of the .NET family, for example,) most languages' standard libraries are written in that language for two very good reasons: because it will share the same set of syntactical definitions, function calling conventions, and the general "look and feel" of the language, and because the people who are likely to write a standard library for a programming language are its users, and particularly its designer(s). So there's nothing unique there; that's pretty standard. And again, there's nothing unique or unusual about a language's compiler being written in itself. C compilers are written in C. Pascal compilers are written in Pascal. Mono's C# compiler is written in C#. Heck, even some scripting languages have implementations "written in itself". So what does it mean that Lisp is unusual in being written in itself?

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  • How to use the Request URL/URL Rewriting For Localization in ASP.NET - Using an HTTP Module or Globa

    - by LocalizedUrlDMan
    I wanted to see if there is a way to use the request URL/URL rewriting to set the language a page is rendered in by examining a portion of the URL in ASP.NET. We have a site that already works with ASP.NET’s resource localization and user’s can change the language that they see pages/resources on the site in, however the current mechanism in not very search engine friendly since the language variations for each language all appear as one page. It would be much better if we could have pages like www.site.com/en-mx/realfolder/realpage.aspx that allow linking to culture specific versions of a page. I know lots of people have likely done localization through URL structures before and I wanted to know if one of your could share how to do this in the Global.asax file or with an HTTP Module (pointing to links to blog postings would be great too). We have a restriction that the site is based on ASP.NET 2.0 (so we can't used the 3.5+ features yet). Here is the example scenario: A real page exits at: www.site.com/realfolder/realpage.aspx The page has a mechanism for the user to change the language it is displayed in via a dropdown. There are search engine optimization and user links sharing benefits to doing this since people can link directly to a page that has content that is applicable to a certain language (this could also include right-to-left layouts for languages like Japanese). I would like to use an HTTP module to see if the first part of the URL after www.site.com, site.com, subdomain.site.com, etc. contains a valid culture code (e.g. en-us, es-mx) then use that value to set the localization culture of the page/resources based on that URL. So if the user accesses the URL www.site.com/en-MX/realfolder/realpage.aspx Then the page will render in Mexico’s variant of Spanish. If the user goes to www.site.com/realfolder/realpage.aspx directly the page would just use their browser’s language settings.

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  • How to install DBD::mysql on OS X server?

    - by Zoran Simic
    Trying to install DBD::mysql on OS X Server 10.6 (mac mini server). But I'm missing the mysql headers apparently. Since mysql is already part of OS X Server 10.6, I would like to NOT install anything else (no fink or darwin ports installs), just whatever's needed to get DBD::mysql installed and working. Do you know how I could do that? Do I have to install the headers somewhere? And if so, where? (again: I don't want to install another version of mysql on the box, want to use the version it came with). Is there a way to install DBD::mysql without compiling any C files? This is the error I get (the actual error is much longer, but these are the most meaningful bits, this is the first error reported). Checking if your kit is complete... Looks good Unrecognized argument in LIBS ignored: '-pipe' Note (probably harmless): No library found for -lmysqlclient Multiple copies of Driver.xst found in: /Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI/ /System/Library/Perl/Extras/5.10.0/darwin-thread-multi-2level/auto/DBI/ at Makefile.PL line 907 Using DBI 1.611 (for perl 5.010000 on darwin-thread-multi-2level) installed in /Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI/ Writing Makefile for DBD::mysql cp lib/DBD/mysql.pm blib/lib/DBD/mysql.pm cp lib/DBD/mysql/GetInfo.pm blib/lib/DBD/mysql/GetInfo.pm cp lib/DBD/mysql/INSTALL.pod blib/lib/DBD/mysql/INSTALL.pod cp lib/Bundle/DBD/mysql.pm blib/lib/Bundle/DBD/mysql.pm gcc-4.2 -c -I/Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI -I/usr/include -fno-omit-frame-pointer -pipe -D_P1003_1B_VISIBLE -DSIGNAL_WITH_VIO_CLOSE -DSIGNALS_DONT_BREAK_READ -DIGNORE_SIGHUP_SIGQUIT -DDBD_MYSQL_INSERT_ID_IS_GOOD -g -arch x86_64 -arch i386 -arch ppc -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -I/usr/local/include -Os -DVERSION=\"4.014\" -DXS_VERSION=\"4.014\" "-I/System/Library/Perl/5.10.0/darwin-thread-multi-2level/CORE" dbdimp.c In file included from dbdimp.c:20: dbdimp.h:22:49: error: mysql.h: No such file or directory dbdimp.h:23:45: error: mysqld_error.h: No such file or directory dbdimp.h:25:49: error: errmsg.h: No such file or directory

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  • jquery fade an element in when a link is clicked and then swap the element when another link is clic

    - by Nik
    I have worked out how to fade an element in: Click here to view the page If you click on the heading Posture 1 : Standing Deep Breathing : you will notice the element fades in as it should. If you now click on posture 2 you will see the element fades in below posture 1. I need to be able to swap posture 1 with posture 2. I have a total of 26 postures that all have images that need to fade in and then be swapped with another image when another heading is clicked. $(document).ready(function(){ $('#section_Q_01,#section_Q_02').hide(); $('h5.trigger#Q_01').click(function(){ $('#section_Q_01').fadeIn(2000) ; }); $('h5.trigger#Q_02').click(function(){ $('#section_Q_02').fadeIn(5000) ; }); }); and the html <div id="section_Q_01" class="01"> <div class="pics"> <img src="../images/multi/poses/pose1/Pranayama._01.jpg"/> <img src="../images/multi/poses/pose1/Pranayama._02.jpg"/> <img src="../images/multi/poses/pose1/Pranayama._03.jpg"/> </div> </div> <div id="section_Q_02" class="02"> <div class="pics"> <img src="../images/multi/poses/pose2/Half_Moon_Pose_04.jpg" /> <img src="../images/multi/poses/pose2/Backward_Bending_05.jpg" /> <img src="../images/multi/poses/pose2/Hands_to_Feet_Pose_06.jpg" /> </div> </div> I need to be able to swap a total of 26 elements #section_Q_01 - #section_Q_26 Any help appreciated

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  • AxCMS.net 10 with Microsoft Silverlight 4 and Microsoft Visual Studio 2010

    - by Axinom
    Axinom, European WCM vendor, today announced the next version of its WCM solution AxCMS.net 10, which streamlines the processes involved in creating, managing and distributing corporate content on the internet. The new solution helps reducing ongoing costs for managing and distributing to large audiences, while at the same time drastically reducing time-to-market and one-time setup costs. http://www.AxCMS.net Axinom’s WCM portfolio, based on the Microsoft .NET Framework 4, Microsoft Visual Studio 2010 and Microsoft Silverlight 4, allows enterprises to increase process efficiency, reduce operating costs and more effectively manage delivery of rich media assets on the Web and mobile devices. Axinom solutions are widely used by major European online brands in IT, telco, retail, media and entertainment industries such as Siemens, American Express, Microsoft Corp., ZDF, Pro7Sat1 Media, and Deutsche Post. Brand New User Interface built with Silverlight 4By using Silverlight 4, Axinom’s team created a new user interface for AxCMS.net 10 that is optimized for improved usability and speed. WYSIWYG mode, integrated image editor, extended list views, and detail views of objects allow a substantial acceleration of typical editor tasks. Axinom’s team worked with Silverlight Rough Cut Editor for video management and Silverlight Analytics Framework for extended reporting to complete the wide range of capabilities included in the new release. “Axinom’s release of AxCMS.net 10 enables developers to take advantage of the latest features in Silverlight 4,” said Brian Goldfarb, director of the developer platform group at Microsoft Corp. “Microsoft is excited about the opportunity this creates for Web developers to streamline the creating, managing and distributing of online corporate content using AxCMS.net 10 and Silverlight.” Rapid Web Development with Visual Studio 2010AxCMS.net 10 is extended by additional products that enable developers to get productive quickly and help solve typical customer scenarios. AxCMS.net template projects come with documented source code that help kick-start projects and learn best practices in all aspects of Web application development. AxCMS.net overcomes many hard-to-solve technical obstacles in an out-of-the-box manner by providing a set of ready-to-use vertical solutions such as corporate Web site, Web shop, Web campaign management, email marketing, multi-channel distribution, management of rich Internet applications, and Web business intelligence. Extended Multi-Site ManagementAxCMS.net has been supporting the management of an unlimited number of Web sites for a long time. The new version 10 of AxCMS.net will further improve multi-site management and provide features to editors and developers that will simplify and accelerate multi-site and multi-language management. Extended publication workflow will take into account additional dependencies of dynamic objects, pages, and documents. “The customer requests evolved from static html pages to dynamic Web applications content with the emergence of rich media assets seamlessly combined across many channels including Web, mobile and IPTV. With the.NET Framework 4 and Silverlight 4, we’re on the fast track to making the three screen strategy a reality for our customers,” said Damir Tomicic, CEO of Axinom Group. “Our customers enjoy substantial competitive advantages of using latest Microsoft technologies. We have a long-standing, relationship with Microsoft and are committed to continued development using Microsoft tools and technologies to deliver innovative Web solutions in the future.”  

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  • How do I install Citrix receiver?

    - by krondor
    Has anyone managed to get the Citrix receiver client working in 64-bit Natty (11.04). It seems libmotif4 won't install multi-arch (32 bit and 64 bit libraries). I also see crazy dependency errors despite the libraries being present. Here is what I received initially when trying to install icaclient.deb from Citrix; sudo dpkg -i Downloads/icaclient_11.100_i386.patched.deb dpkg: error processing Downloads/icaclient_11.100_i386.patched.deb (--install): package architecture (i386) does not match system (amd64) Errors were encountered while processing: Downloads/icaclient_11.100_i386.patched.deb I then installed the 32 bit libraries. sudo apt-get install ia32-libs ia32-libs-gtk Then I noticed libmotif4 (a dependency of the citrix client) wasn't present so I installed the 64bit version. sudo apt-get install libmotif4 I then tried to force the 32 bit version; sudo dpkg --force-architecture -i Downloads/libmotif4_2.3.3-5_i386.deb dpkg: warning: overriding problem because --force enabled: package architecture (i386) does not match system (amd64) Selecting previously deselected package libmotif4:i386. dpkg: error processing Downloads/libmotif4_2.3.3-5_i386.deb (--install): libmotif4:i386 2.3.3-5 (Multi-Arch: no) is not co-installable with libmotif4:amd64 2.3.3-5ubuntu1 (Multi-Arch: no) which is currently installed So I uninstalled the 64 bit version and tried to install the 32 bit version. This worked, but when I attempt to install Citrix I enter dependency hell. sudo dpkg --force-architecture -i Downloads/icaclient_11.100_i386.patched.deb dpkg: warning: overriding problem because --force enabled: package architecture (i386) does not match system (amd64) Selecting previously deselected package icaclient:i386. (Reading database ... 183036 files and directories currently installed.) Unpacking icaclient:i386 (from .../icaclient_11.100_i386.patched.deb) ... dpkg: dependency problems prevent configuration of icaclient:i386: icaclient:i386 depends on libc6 (>= 2.3). icaclient:i386 depends on libice6 (>= 1:1.0.0). icaclient:i386 depends on libsm6. icaclient:i386 depends on libx11-6. icaclient:i386 depends on libxaw7. icaclient:i386 depends on libxext6. icaclient:i386 depends on libxmu6. icaclient:i386 depends on libxp6. icaclient:i386 depends on libxpm4. icaclient:i386 depends on libxt6. dpkg: error processing icaclient:i386 (--install): dependency problems - leaving unconfigured Errors were encountered while processing: icaclient:i386 So the state it's in, there's no icaclient binaries installed only the docs. It is complaining about libraries that are indeed present (libc6 64 bit and 32 bit). libmotif4 is only 32 bit installed and won't install alongside libmotif4 64 bit. libmotif4 error when you try to install it alongside the 32bit instance; libmotif4:amd64 2.3.3-5 (Multi-Arch: no) is not co-installable with libmotif4:i386 2.3.3-5ubuntu1 (Multi-Arch: no) which is currently installed Any tips?

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  • Why is multithreading often preferred for improving performance?

    - by user1849534
    I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approaches here: an async approach basically based on signals, or just an async approach as called by many papers and languages like the new C# 5.0 for example, and a "companion thread" that manages the policy of your pipeline a concurrent approach or multi-threading approach I will just say that I'm thinking about the hardware here and the worst case scenario, and I have tested this 2 paradigms myself, the async paradigm is a winner at the point that I don't get why people 90% of the time talk about multi-threading when they want to speed up things or make a good use of their resources. I have tested multi-threaded programs and async program on an old machine with an Intel quad-core that doesn't offer a memory controller inside the CPU, the memory is managed entirely by the motherboard, well in this case performances are horrible with a multi-threaded application, even a relatively low number of threads like 3-4-5 can be a problem, the application is unresponsive and is just slow and unpleasant. A good async approach is, on the other hand, probably not faster but it's not worst either, my application just waits for the result and doesn't hangs, it's responsive and there is a much better scaling going on. I have also discovered that a context change in the threading world it's not that cheap in real world scenario, it's in fact quite expensive especially when you have more than 2 threads that need to cycle and swap among each other to be computed. On modern CPUs the situation it's not really that different, the memory controller it's integrated but my point is that an x86 CPUs is basically a serial machine and the memory controller works the same way as with the old machine with an external memory controller on the motherboard. The context switch is still a relevant cost in my application and the fact that the memory controller it's integrated or that the newer CPU have more than 2 core it's not bargain for me. For what i have experienced the concurrent approach is good in theory but not that good in practice, with the memory model imposed by the hardware, it's hard to make a good use of this paradigm, also it introduces a lot of issues ranging from the use of my data structures to the join of multiple threads. Also both paradigms do not offer any security abut when the task or the job will be done in a certain point in time, making them really similar from a functional point of view. According to the X86 memory model, why the majority of people suggest to use concurrency with C++ and not just an async approach ? Also why not considering the worst case scenario of a computer where the context switch is probably more expensive than the computation itself ?

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  • MediaWiki migrated from Tiger to Snow Leopard throwing an exceptions

    - by Matt S
    I had an old laptop running Mac OS X 10.4 with macports for web development: Apache 2, PHP 5.3.2, Mysql 5, etc. I got a new laptop running Mac OS X 10.6 and installed macports. I installed the same web development apps: Apache 2, PHP 5.3.2, Mysql 5, etc. All versions the same as my old laptop. A Mediawiki site (version 1.15) was copied over from my old system (via the Migration Assistant). Having a fresh Mysql setup, I dumped my old database and imported it on the new system. When I try to browse to mediawiki's "Special" pages, I get the following exception thrown: Invalid language code requested Backtrace: #0 /languages/Language.php(2539): Language::loadLocalisation(NULL) #1 /includes/MessageCache.php(846): Language::getFallbackFor(NULL) #2 /includes/MessageCache.php(821): MessageCache->processMessagesArray(Array, NULL) #3 /includes/GlobalFunctions.php(2901): MessageCache->loadMessagesFile('/Users/matt/Sit...', false) #4 /extensions/OpenID/OpenID.setup.php(181): wfLoadExtensionMessages('OpenID') #5 [internal function]: OpenIDLocalizedPageName(Array, 'en') #6 /includes/Hooks.php(117): call_user_func_array('OpenIDLocalized...', Array) #7 /languages/Language.php(1851): wfRunHooks('LanguageGetSpec...', Array) #8 /includes/SpecialPage.php(240): Language->getSpecialPageAliases() #9 /includes/SpecialPage.php(262): SpecialPage::initAliasList() #10 /includes/SpecialPage.php(406): SpecialPage::resolveAlias('UserLogin') #11 /includes/SpecialPage.php(507): SpecialPage::getPageByAlias('UserLogin') #12 /includes/Wiki.php(229): SpecialPage::executePath(Object(Title)) #13 /includes/Wiki.php(59): MediaWiki->initializeSpecialCases(Object(Title), Object(OutputPage), Object(WebRequest)) #14 /index.php(116): MediaWiki->initialize(Object(Title), NULL, Object(OutputPage), Object(User), Object(WebRequest)) #15 {main} I tried to step through Mediawiki's code, but it's a mess. There are global variables everywhere. If I change the code slightly to get around the exception, the page comes up blank and there are no errors (implying there are multiple problems). Anyone else get Mediawiki 1.15 working on OS X 10.6 with macports? Anything in the migration from Tiger that could cause a problem? Any clues where to look for answers?

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  • When is a SQL function not a function?

    - by Rob Farley
    Should SQL Server even have functions? (Oh yeah – this is a T-SQL Tuesday post, hosted this month by Brad Schulz) Functions serve an important part of programming, in almost any language. A function is a piece of code that is designed to return something, as opposed to a piece of code which isn’t designed to return anything (which is known as a procedure). SQL Server is no different. You can call stored procedures, even from within other stored procedures, and you can call functions and use these in other queries. Stored procedures might query something, and therefore ‘return data’, but a function in SQL is considered to have the type of the thing returned, and can be used accordingly in queries. Consider the internal GETDATE() function. SELECT GETDATE(), SomeDatetimeColumn FROM dbo.SomeTable; There’s no logical difference between the field that is being returned by the function and the field that’s being returned by the table column. Both are the datetime field – if you didn’t have inside knowledge, you wouldn’t necessarily be able to tell which was which. And so as developers, we find ourselves wanting to create functions that return all kinds of things – functions which look up values based on codes, functions which do string manipulation, and so on. But it’s rubbish. Ok, it’s not all rubbish, but it mostly is. And this isn’t even considering the SARGability impact. It’s far more significant than that. (When I say the SARGability aspect, I mean “because you’re unlikely to have an index on the result of some function that’s applied to a column, so try to invert the function and query the column in an unchanged manner”) I’m going to consider the three main types of user-defined functions in SQL Server: Scalar Inline Table-Valued Multi-statement Table-Valued I could also look at user-defined CLR functions, including aggregate functions, but not today. I figure that most people don’t tend to get around to doing CLR functions, and I’m going to focus on the T-SQL-based user-defined functions. Most people split these types of function up into two types. So do I. Except that most people pick them based on ‘scalar or table-valued’. I’d rather go with ‘inline or not’. If it’s not inline, it’s rubbish. It really is. Let’s start by considering the two kinds of table-valued function, and compare them. These functions are going to return the sales for a particular salesperson in a particular year, from the AdventureWorks database. CREATE FUNCTION dbo.FetchSales_inline(@salespersonid int, @orderyear int) RETURNS TABLE AS  RETURN (     SELECT e.LoginID as EmployeeLogin, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ) ; GO CREATE FUNCTION dbo.FetchSales_multi(@salespersonid int, @orderyear int) RETURNS @results TABLE (     EmployeeLogin nvarchar(512),     OrderDate datetime,     SalesOrderID int     ) AS BEGIN     INSERT @results (EmployeeLogin, OrderDate, SalesOrderID)     SELECT e.LoginID, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ;     RETURN END ; GO You’ll notice that I’m being nice and responsible with the use of the DATEADD function, so that I have SARGability on the OrderDate filter. Regular readers will be hoping I’ll show what’s going on in the execution plans here. Here I’ve run two SELECT * queries with the “Show Actual Execution Plan” option turned on. Notice that the ‘Query cost’ of the multi-statement version is just 2% of the ‘Batch cost’. But also notice there’s trickery going on. And it’s nothing to do with that extra index that I have on the OrderDate column. Trickery. Look at it – clearly, the first plan is showing us what’s going on inside the function, but the second one isn’t. The second one is blindly running the function, and then scanning the results. There’s a Sequence operator which is calling the TVF operator, and then calling a Table Scan to get the results of that function for the SELECT operator. But surely it still has to do all the work that the first one is doing... To see what’s actually going on, let’s look at the Estimated plan. Now, we see the same plans (almost) that we saw in the Actuals, but we have an extra one – the one that was used for the TVF. Here’s where we see the inner workings of it. You’ll probably recognise the right-hand side of the TVF’s plan as looking very similar to the first plan – but it’s now being called by a stack of other operators, including an INSERT statement to be able to populate the table variable that the multi-statement TVF requires. And the cost of the TVF is 57% of the batch! But it gets worse. Let’s consider what happens if we don’t need all the columns. We’ll leave out the EmployeeLogin column. Here, we see that the inline function call has been simplified down. It doesn’t need the Employee table. The join is redundant and has been eliminated from the plan, making it even cheaper. But the multi-statement plan runs the whole thing as before, only removing the extra column when the Table Scan is performed. A multi-statement function is a lot more powerful than an inline one. An inline function can only be the result of a single sub-query. It’s essentially the same as a parameterised view, because views demonstrate this same behaviour of extracting the definition of the view and using it in the outer query. A multi-statement function is clearly more powerful because it can contain far more complex logic. But a multi-statement function isn’t really a function at all. It’s a stored procedure. It’s wrapped up like a function, but behaves like a stored procedure. It would be completely unreasonable to expect that a stored procedure could be simplified down to recognise that not all the columns might be needed, but yet this is part of the pain associated with this procedural function situation. The biggest clue that a multi-statement function is more like a stored procedure than a function is the “BEGIN” and “END” statements that surround the code. If you try to create a multi-statement function without these statements, you’ll get an error – they are very much required. When I used to present on this kind of thing, I even used to call it “The Dangers of BEGIN and END”, and yes, I’ve written about this type of thing before in a similarly-named post over at my old blog. Now how about scalar functions... Suppose we wanted a scalar function to return the count of these. CREATE FUNCTION dbo.FetchSales_scalar(@salespersonid int, @orderyear int) RETURNS int AS BEGIN     RETURN (         SELECT COUNT(*)         FROM Sales.SalesOrderHeader AS o         LEFT JOIN HumanResources.Employee AS e         ON e.EmployeeID = o.SalesPersonID         WHERE o.SalesPersonID = @salespersonid         AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')         AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ); END ; GO Notice the evil words? They’re required. Try to remove them, you just get an error. That’s right – any scalar function is procedural, despite the fact that you wrap up a sub-query inside that RETURN statement. It’s as ugly as anything. Hopefully this will change in future versions. Let’s have a look at how this is reflected in an execution plan. Here’s a query, its Actual plan, and its Estimated plan: SELECT e.LoginID, y.year, dbo.FetchSales_scalar(p.SalesPersonID, y.year) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; We see here that the cost of the scalar function is about twice that of the outer query. Nicely, the query optimizer has worked out that it doesn’t need the Employee table, but that’s a bit of a red herring here. There’s actually something way more significant going on. If I look at the properties of that UDF operator, it tells me that the Estimated Subtree Cost is 0.337999. If I just run the query SELECT dbo.FetchSales_scalar(281,2003); we see that the UDF cost is still unchanged. You see, this 0.0337999 is the cost of running the scalar function ONCE. But when we ran that query with the CROSS JOIN in it, we returned quite a few rows. 68 in fact. Could’ve been a lot more, if we’d had more salespeople or more years. And so we come to the biggest problem. This procedure (I don’t want to call it a function) is getting called 68 times – each one between twice as expensive as the outer query. And because it’s calling it in a separate context, there is even more overhead that I haven’t considered here. The cheek of it, to say that the Compute Scalar operator here costs 0%! I know a number of IT projects that could’ve used that kind of costing method, but that’s another story that I’m not going to go into here. Let’s look at a better way. Suppose our scalar function had been implemented as an inline one. Then it could have been expanded out like a sub-query. It could’ve run something like this: SELECT e.LoginID, y.year, (SELECT COUNT(*)     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = p.SalesPersonID     AND o.OrderDate >= DATEADD(year,y.year-2000,'20000101')     AND o.OrderDate < DATEADD(year,y.year-2000+1,'20000101')     ) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; Don’t worry too much about the Scan of the SalesOrderHeader underneath a Nested Loop. If you remember from plenty of other posts on the matter, execution plans don’t push the data through. That Scan only runs once. The Index Spool sucks the data out of it and populates a structure that is used to feed the Stream Aggregate. The Index Spool operator gets called 68 times, but the Scan only once (the Number of Executions property demonstrates this). Here, the Query Optimizer has a full picture of what’s being asked, and can make the appropriate decision about how it accesses the data. It can simplify it down properly. To get this kind of behaviour from a function, we need it to be inline. But without inline scalar functions, we need to make our function be table-valued. Luckily, that’s ok. CREATE FUNCTION dbo.FetchSales_inline2(@salespersonid int, @orderyear int) RETURNS table AS RETURN (SELECT COUNT(*) as NumSales     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ); GO But we can’t use this as a scalar. Instead, we need to use it with the APPLY operator. SELECT e.LoginID, y.year, n.NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID OUTER APPLY dbo.FetchSales_inline2(p.SalesPersonID, y.year) AS n; And now, we get the plan that we want for this query. All we’ve done is tell the function that it’s returning a table instead of a single value, and removed the BEGIN and END statements. We’ve had to name the column being returned, but what we’ve gained is an actual inline simplifiable function. And if we wanted it to return multiple columns, it could do that too. I really consider this function to be superior to the scalar function in every way. It does need to be handled differently in the outer query, but in many ways it’s a more elegant method there too. The function calls can be put amongst the FROM clause, where they can then be used in the WHERE or GROUP BY clauses without fear of calling the function multiple times (another horrible side effect of functions). So please. If you see BEGIN and END in a function, remember it’s not really a function, it’s a procedure. And then fix it. @rob_farley

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  • Question about POP3 message termination octet

    - by user361633
    This is from the POP3 RFC. "Responses to certain commands are multi-line. In these cases, which are clearly indicated below, after sending the first line of the response and a CRLF, any additional lines are sent, each terminated by a CRLF pair. When all lines of the response have been sent, a final line is sent, consisting of a termination octet (decimal code 046, ".") and a CRLF pair. If any line of the multi-line response begins with the termination octet, the line is "byte-stuffed" by pre-pending the termination octet to that line of the response. Hence a multi-line response is terminated with the five octets "CRLF.CRLF". When examining a multi-line response, the client checks to see if the line begins with the termination octet. If so and if octets other than CRLF follow, the first octet of the line (the termination octet) is stripped away. If so and if CRLF immediately follows the termination character, then the response from the POP server is ended and the line containing ".CRLF" is not considered part of the multi-line response." Well, i have problem with this, for example gmail sometimes sends the termination octet and then in the NEXT LINE sends the CRLF pair. For example: "+OK blah blah" "blah blah." "\r\n" That's very rare, but it happens sometimes, so obviously i'm unable to determine the end of the message in such case, because i'm expecting a line that consists of '.\r\n'. Seriously, is Gmail violating the POP3 protocol or i'm doing something wrong? Also i have a second question, english is not my first language so i cannot understand that completely: "If any line of the multi-line response begins with the termination octet, the line is "byte-stuffed" by pre-pending the termination octet to that line of the response. Hence a multi-line response is terminated with the five octets "CRLF.CRLF"." When exactly CRLF.CRLF is used? Can someone gives me a simple example? The rfc says that is used when any line of the response begins with the termination octet. But i don't see any lines that starts with '.' in the messages that are terminated with CRLF.CRLF. I checked that. Maybe i don't understand something, that's why i'm asking.

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  • Mac OS X 10.6 Setup for Apache/MySQL/Perl

    - by Russell C.
    I just got a new Mac and have been trying to setup a local development environment for my perl applications for a few days now with no luck. I'm getting no where fast so I hope someone else who has done this successfully could help. I started by installing MAMP which I thought would take care of everything for me but unfortunately it doesn't take care of some important perl modules. I used CPAN to install all our required modules except that it seems DBD::mysql doesn't install correctly through CPAN. After reading a lot online, lots of people reported problems with this and recommended using MacPorts to install the module which I have tried doing with no luck using the following command: sudo port install p5-dbd-mysql After what seems like a successful install of DBD::mysql, Apache continues to report the following error when trying to run any of our Perl scripts: [Fri Apr 30 18:51:07 2010] [error] [client 127.0.0.1] install_driver(mysql) failed: Can't locate DBD/mysql.pm in @INC (@INC contains: /Library/Perl/Updates/5.10.0/darwin-thread-multi-2level /Library/Perl/Updates/5.10.0 /System/Library/Perl/5.10.0/darwin-thread-multi-2level /System/Library/Perl/5.10.0 /Library/Perl/5.10.0/darwin-thread-multi-2level /Library/Perl/5.10.0 /Network/Library/Perl/5.10.0/darwin-thread-multi-2level /Network/Library/Perl/5.10.0 /Network/Library/Perl /System/Library/Perl/Extras/5.10.0/darwin-thread-multi-2level /System/Library/Perl/Extras/5.10.0 .) at (eval 1835) line 3. [Fri Apr 30 18:51:07 2010] [error] [client 127.0.0.1] Perhaps the DBD::mysql perl module hasn't been fully installed, [Fri Apr 30 18:51:07 2010] [error] [client 127.0.0.1] or perhaps the capitalisation of 'mysql' isn't right. [Fri Apr 30 18:51:07 2010] [error] [client 127.0.0.1] Available drivers: DBM, ExampleP, File, Gofer, Proxy, SQLite, Sponge. I'm not sure where to go from here but my Mac isn't much of a development environment if Perl isn't able to talk to the database. I'd really appreciate any help and advice you might be able to provide in getting my system setup successfully. Thanks in advance!

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  • Choosing a Windows Automation script language. Autoit vs Autohotkey.

    - by PA
    I need to choose a windows automation program. Which one do you recommend? AutoIt, AutoHotkey, others? I have read http://paperlined.org/apps/autohotkey/autoit_and_autohotkey.html , interesting history but without a clear recommendation. Searching on google leaves a winner (around 312k hits for AutoHotkey Windows vs 482k hits for AutoIt Windows). In StackOverflow there are 15 questions tagged as AutoIt vs 18 for AutoHotkey. I am interested on your opinion as programmers. Which one do you think is easier to use, more deployable and more powerful in terms of functionality? Note: I have already used AutoHotkey for personal use. So my initial preference is for this.

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  • Is Objective-C++ a totally different language from Objective-C?

    - by Jake Petroules
    As the title says... are they considered different languages? For example if you've written an application using a combination of C++ and Objective-C++ would you consider it to have been written in C++ and Objective-C, C++ and Objective-C++ or all three? Obviously C and C++ are different languages even though C++ and C are directly compatible, how is the situation with Objective-C++ and Objective-C?

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  • Is there an "opposite" to the null coalescing operator? (…in any language?)

    - by Jay
    null coalescing translates roughly to return x, unless it is null, in which case return y I often need return null if x is null, otherwise return x.y I can use return x == null ? null : x.y; Not bad, but that null in the middle always bothers me -- it seems superfluous. I'd prefer something like return x :: x.y;, where what follows the :: is evaluated only if what precedes it is not null. I see this as almost an opposite to null coalescence, kind of mixed in with a terse, inline null-check, but I'm [almost] certain that there is no such operator in C#. Are there other languages that have such an operator? If so, what is it called? (I know that I can write a method for it in C#; I use return NullOrValue.of(x, () => x.y);, but if you have anything better, I'd like to see that too.)

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  • Is the valid state domain of a program a regular language?

    - by BCS
    If you look at the call stack of a program and treat each return pointer as a token, what kind of automata is needed to build a recognizer for the valid states of the program? As a corollary, what kind of automata is needed to build a recognizer for a specific bug state? My thought is that if these form regular languages than some interesting tools could be built around that. E.g. given a set of crash/failure dumps, automatically group them and generate a recognizer to identify new instances of know bugs.

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  • i am using winsock2.h in c language the following errors are unuderstandable help required?

    - by moon
    i am going to paste here my code an errors :::: #include "stdio.h" #include "winsock2.h" #define SIO_RCVALL _WSAIOW(IOC_VENDOR,1) //this removes the need of mstcpip.h void StartSniffing (SOCKET Sock); //This will sniff here and there void ProcessPacket (unsigned char* , int); //This will decide how to digest void PrintIpHeader (unsigned char* , int); void PrintUdpPacket (unsigned char* , int); void ConvertToHex (unsigned char* , unsigned int); void PrintData (unsigned char* , int); //IP Header Structure typedef struct ip_hdr { unsigned char ip_header_len:4; // 4-bit header length (in 32-bit words) normally=5 (Means 20 Bytes may be 24 also) unsigned char ip_version :4; // 4-bit IPv4 version unsigned char ip_tos; // IP type of service unsigned short ip_total_length; // Total length unsigned short ip_id; // Unique identifier unsigned char ip_frag_offset :5; // Fragment offset field unsigned char ip_more_fragment :1; unsigned char ip_dont_fragment :1; unsigned char ip_reserved_zero :1; unsigned char ip_frag_offset1; //fragment offset unsigned char ip_ttl; // Time to live unsigned char ip_protocol; // Protocol(TCP,UDP etc) unsigned short ip_checksum; // IP checksum unsigned int ip_srcaddr; // Source address unsigned int ip_destaddr; // Source address } IPV4_HDR; //UDP Header Structure typedef struct udp_hdr { unsigned short source_port; // Source port no. unsigned short dest_port; // Dest. port no. unsigned short udp_length; // Udp packet length unsigned short udp_checksum; // Udp checksum (optional) } UDP_HDR; //ICMP Header Structure typedef struct icmp_hdr { BYTE type; // ICMP Error type BYTE code; // Type sub code USHORT checksum; USHORT id; USHORT seq; } ICMP_HDR; FILE *logfile; int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j; struct sockaddr_in source,dest; char hex[2]; //Its free! IPV4_HDR *iphdr; UDP_HDR *udpheader; int main() { SOCKET sniffer; struct in_addr addr; int in; char hostname[100]; struct hostent *local; WSADATA wsa; //logfile=fopen("log.txt","w"); //if(logfile==NULL) printf("Unable to create file."); //Initialise Winsock printf("\nInitialising Winsock..."); if (WSAStartup(MAKEWORD(2,2), &wsa) != 0) { printf("WSAStartup() failed.\n"); return 1; } printf("Initialised"); //Create a RAW Socket printf("\nCreating RAW Socket..."); sniffer = socket(AF_INET, SOCK_RAW, IPPROTO_IP); if (sniffer == INVALID_SOCKET) { printf("Failed to create raw socket.\n"); return 1; } printf("Created."); //Retrive the local hostname if (gethostname(hostname, sizeof(hostname)) == SOCKET_ERROR) { printf("Error : %d",WSAGetLastError()); return 1; } printf("\nHost name : %s \n",hostname); //Retrive the available IPs of the local host local = gethostbyname(hostname); printf("\nAvailable Network Interfaces : \n"); if (local == NULL) { printf("Error : %d.\n",WSAGetLastError()); return 1; } for (i = 0; local->h_addr_list[i] != 0; ++i) { memcpy(&addr, local->h_addr_list[i], sizeof(struct in_addr)); printf("Interface Number : %d Address : %s\n",i,inet_ntoa(addr)); } printf("Enter the interface number you would like to sniff : "); scanf("%d",&in); memset(&dest, 0, sizeof(dest)); memcpy(&dest.sin_addr.s_addr,local->h_addr_list[in],sizeof(dest.sin_addr.s_addr)); dest.sin_family = AF_INET; dest.sin_port = 0; printf("\nBinding socket to local system and port 0 ..."); if (bind(sniffer,(struct sockaddr *)&dest,sizeof(dest)) == SOCKET_ERROR) { printf("bind(%s) failed.\n", inet_ntoa(addr)); return 1; } printf("Binding successful"); //Enable this socket with the power to sniff : SIO_RCVALL is the key Receive ALL ;) j=1; printf("\nSetting socket to sniff..."); if (WSAIoctl(sniffer, SIO_RCVALL,&j, sizeof(j), 0, 0,(LPDWORD)&in,0, 0) == SOCKET_ERROR) { printf("WSAIoctl() failed.\n"); return 1; } printf("Socket set."); //Begin printf("\nStarted Sniffing\n"); printf("Packet Capture Statistics...\n"); StartSniffing(sniffer); //Happy Sniffing //End closesocket(sniffer); WSACleanup(); return 0; } void StartSniffing(SOCKET sniffer) { unsigned char *Buffer = ( unsigned char *)malloc(65536); //Its Big! int mangobyte; if (Buffer == NULL) { printf("malloc() failed.\n"); return; } do { mangobyte = recvfrom(sniffer,(char *)Buffer,65536,0,0,0); //Eat as much as u can if(mangobyte > 0) ProcessPacket(Buffer, mangobyte); else printf( "recvfrom() failed.\n"); } while (mangobyte > 0); free(Buffer); } void ProcessPacket(unsigned char* Buffer, int Size) { iphdr = (IPV4_HDR *)Buffer; ++total; switch (iphdr->ip_protocol) //Check the Protocol and do accordingly... { case 1: //ICMP Protocol ++icmp; //PrintIcmpPacket(Buffer,Size); break; case 2: //IGMP Protocol ++igmp; break; case 6: //TCP Protocol ++tcp; //PrintTcpPacket(Buffer,Size); break; case 17: //UDP Protocol ++udp; PrintUdpPacket(Buffer,Size); break; default: //Some Other Protocol like ARP etc. ++others; break; } printf("TCP : %d UDP : %d ICMP : %d IGMP : %d Others : %d Total : %d\r",tcp,udp,icmp,igmp,others,total); } void PrintIpHeader (unsigned char* Buffer, int Size) { unsigned short iphdrlen; iphdr = (IPV4_HDR *)Buffer; iphdrlen = iphdr->ip_header_len*4; memset(&source, 0, sizeof(source)); source.sin_addr.s_addr = iphdr->ip_srcaddr; memset(&dest, 0, sizeof(dest)); dest.sin_addr.s_addr = iphdr->ip_destaddr; fprintf(logfile,"\n"); fprintf(logfile,"IP Header\n"); fprintf(logfile," |-IP Version : %d\n",(unsigned int)iphdr->ip_version); fprintf(logfile," |-IP Header Length : %d DWORDS or %d Bytes\n",(unsigned int)iphdr->ip_header_len); fprintf(logfile," |-Type Of Service : %d\n",(unsigned int)iphdr->ip_tos); fprintf(logfile," |-IP Total Length : %d Bytes(Size of Packet)\n",ntohs(iphdr->ip_total_length)); fprintf(logfile," |-Identification : %d\n",ntohs(iphdr->ip_id)); fprintf(logfile," |-Reserved ZERO Field : %d\n",(unsigned int)iphdr->ip_reserved_zero); fprintf(logfile," |-Dont Fragment Field : %d\n",(unsigned int)iphdr->ip_dont_fragment); fprintf(logfile," |-More Fragment Field : %d\n",(unsigned int)iphdr->ip_more_fragment); fprintf(logfile," |-TTL : %d\n",(unsigned int)iphdr->ip_ttl); fprintf(logfile," |-Protocol : %d\n",(unsigned int)iphdr->ip_protocol); fprintf(logfile," |-Checksum : %d\n",ntohs(iphdr->ip_checksum)); fprintf(logfile," |-Source IP : %s\n",inet_ntoa(source.sin_addr)); fprintf(logfile," |-Destination IP : %s\n",inet_ntoa(dest.sin_addr)); } void PrintUdpPacket(unsigned char *Buffer,int Size) { unsigned short iphdrlen; iphdr = (IPV4_HDR *)Buffer; iphdrlen = iphdr->ip_header_len*4; udpheader = (UDP_HDR *)(Buffer + iphdrlen); fprintf(logfile,"\n\n***********************UDP Packet*************************\n"); PrintIpHeader(Buffer,Size); fprintf(logfile,"\nUDP Header\n"); fprintf(logfile," |-Source Port : %d\n",ntohs(udpheader->source_port)); fprintf(logfile," |-Destination Port : %d\n",ntohs(udpheader->dest_port)); fprintf(logfile," |-UDP Length : %d\n",ntohs(udpheader->udp_length)); fprintf(logfile," |-UDP Checksum : %d\n",ntohs(udpheader->udp_checksum)); fprintf(logfile,"\n"); fprintf(logfile,"IP Header\n"); PrintData(Buffer,iphdrlen); fprintf(logfile,"UDP Header\n"); PrintData(Buffer+iphdrlen,sizeof(UDP_HDR)); fprintf(logfile,"Data Payload\n"); PrintData(Buffer+iphdrlen+sizeof(UDP_HDR) ,(Size - sizeof(UDP_HDR) - iphdr->ip_header_len*4)); fprintf(logfile,"\n###########################################################"); } void PrintData (unsigned char* data , int Size) { for(i=0 ; i < Size ; i++) { if( i!=0 && i%16==0) //if one line of hex printing is complete... { fprintf(logfile," "); for(j=i-16 ; j<i ; j++) { if(data[j]>=32 && data[j]<=128) fprintf(logfile,"%c",(unsigned char)data[j]); //if its a number or alphabet else fprintf(logfile,"."); //otherwise print a dot } fprintf(logfile,"\n"); } if(i%16==0) fprintf(logfile," "); fprintf(logfile," %02X",(unsigned int)data[i]); if( i==Size-1) //print the last spaces { for(j=0;j<15-i%16;j++) fprintf(logfile," "); //extra spaces fprintf(logfile," "); for(j=i-i%16 ; j<=i ; j++) { if(data[j]>=32 && data[j]<=128) fprintf(logfile,"%c",(unsigned char)data[j]); else fprintf(logfile,"."); } fprintf(logfile,"\n"); } } } following are the errors Error 1 error LNK2019: unresolved external symbol __imp__WSACleanup@0 referenced in function _main sniffer.obj sniffer test Error 2 error LNK2019: unresolved external symbol __imp__closesocket@4 referenced in function _main sniffer.obj sniffer test Error 3 error LNK2019: unresolved external symbol __imp__WSAIoctl@36 referenced in function _main sniffer.obj sniffer test Error 4 error LNK2019: unresolved external symbol __imp__bind@12 referenced in function _main sniffer.obj sniffer test Error 5 error LNK2019: unresolved external symbol __imp__inet_ntoa@4 referenced in function _main sniffer.obj sniffer test Error 6 error LNK2019: unresolved external symbol __imp__gethostbyname@4 referenced in function _main sniffer.obj sniffer test Error 7 error LNK2019: unresolved external symbol __imp__WSAGetLastError@0 referenced in function _main sniffer.obj sniffer test Error 8 error LNK2019: unresolved external symbol __imp__gethostname@8 referenced in function _main sniffer.obj sniffer test Error 9 error LNK2019: unresolved external symbol __imp__socket@12 referenced in function _main sniffer.obj sniffer test Error 10 error LNK2019: unresolved external symbol __imp__WSAStartup@8 referenced in function _main sniffer.obj sniffer test Error 11 error LNK2019: unresolved external symbol __imp__recvfrom@24 referenced in function "void __cdecl StartSniffing(unsigned int)" (?StartSniffing@@YAXI@Z) sniffer.obj sniffer test Error 12 error LNK2019: unresolved external symbol __imp__ntohs@4 referenced in function "void __cdecl PrintIpHeader(unsigned char *,int)" (?PrintIpHeader@@YAXPAEH@Z) sniffer.obj sniffer test Error 13 fatal error LNK1120: 12 unresolved externals E:\CWM\sniffer test\Debug\sniffer test.exe sniffer test

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  • Why we used double and triple pointer in objective-C or C language?

    - by Rajendra Bhole
    Hi, I confused when i want to take single pointer and when should i take double pointer? In following structure what exactly did? struct objc_class { Class isa; Class super_class; const char *name; long version; long info; long instance_size; struct objc_ivar_list *ivars; struct objc_method_list **methodLists; struct objc_cache *cache; struct objc_protocol_list *protocols; }; Why we use the "**methodLists" double pointer. Edited int sqlite3_get_table( sqlite3 *db, const char zSql, char **pazResult, int *pnRow, int *pnColumn, char *pzErrmsg ); In above scenario what will be meaning of triple pointer char **pazResult?

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  • Why Java language does not offer a way to declare getters and setters of a given "field" through ann

    - by zim2001
    I actually happily design and develop JEE Applications for quite 9 years, but I realized recently that as time goes by, I feel more and more fed up of dragging all these ugly bean classes with their bunch of getters and setters. Considering a basic bean like this : public class MyBean { // needs getter AND setter private int myField1; // needs only a getter, no setter private int myField2; // needs only a setter, no getter private int myField3; /** * Get the field1 * @return the field1 */ public int getField1() { return myField1; } /** * Set the field1 * @param value the value */ public void setField1(int value) { myField1 = value; } /** * Get the field2 * @return the field2 */ public int getField2() { return myField2; } /** * Set the field3 * @param value the value */ public void setField3(int value) { myField3 = value; } } I'm dreaming of something like this : public class MyBean { @inout(public,public) private int myField1; @out(public) private int myField2; @in(public) private int myField3; } No more stupid javadoc, just tell the important thing... It would still be possible to mix annotation and written down getters or setters, to cover cases when it should do non-trivial sets and gets. In other words, annotation would auto-generate the getter / setter code piece except when a literate one is provided. Moreover, I'm also dreaming of replacing things like that : MyBean b = new MyBean(); int v = b.getField1(); b.setField3(v+1); by such : MyBean b = new MyBean(); int v = b.field1; b.field3 = v+1; In fact, writing "b.field1" on the right side of an expression would be semantically identical to write "b.getField1()", I mean as if it has been replaced by some kind of a preprocessor. It's just an idea but I'm wondering if I'm alone on that topic, and also if it has major flaws. I'm aware that this question doesn't exactly meet the SO credo (we prefer questions that can be answered, not just discussed) so I flag it community wiki...

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  • Is there an extensible SQL like query language that is safe for exposing via a public API?

    - by Lokkju
    I want to expose some spatial (and a few non-spatial) datasets via a public API. The backend store will either be PostgreSQL/PostGIS, sqlite/spatialite, or CouchDB/GeoCouch. My goal is to find a some, preferably standard, way to allow people to make complex spatial queries against the data. I would like it to be a simple GET based request. The idea is to allow safe SQL type queries, without allowing unsafe ones. I would rather modify something that is off the shelf than doing the entire thing myself. I specifically want to support requesting specific fields from a table; joining results; and spatial functions that are already implemented by the underlying datastore. Ideas anyone?

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  • How you would you describe the Observer pattern in beginner language?

    - by Sheldon
    Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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  • VCL/Delphi/BCB - which IDE/language should I use?

    - by mawg
    I bought Delphi 1 when it came out - and was hooked. When BCB came out (around D3, iirc), I switched, mainly because I have used C/C++ professionally for a few decades. I have "been away" for 7 or 8 years and am now returning. I still have BCB 6 & Delphi 7 (not to mention Kylix). I always felt more comfortable with C++ than Pascal - purely because of work-day familiarity. But, realistically, iirc, most 3rd party VCL components are coded in Delphi/Pascal. And I think I used to have problems debugging Delphi components from BCB, but I could well remember wrongly. Anyhoo, now I am back and intend to use VCL components / hack the code of same / debug them & code a few of my own. Given that I am slightly more comfortable with C++, is there any compelling reason to choose Delphi over BCB, or is this just a case of how long my particular piece of string is?

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