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• how to use shared variable using stored procedure in crystal reports

  - by sonia

  i have a parent report and it contains a two sub report. * subreport: item which get all fields from store procedure named spGetReportItem. like ItemName ItemQuantity TotalItemCost ab 4 45 dd 6 98 *subreport: Labour which get all fields from store procedure named spGetReportLabour. like labourName labourQuantity TotalLabourCost ab 44 455 dd 63 986 i want to find the total of totalitemcost and total of totallabourcost and then want grandtotal of totalitemcost and totallabourcost. i have seen many examples on internet in which shared variable is used in the formula bt the problem is that they have used the table but i m fetching data from stored procedure. so how can i access the stored procedure fields for calculation. like i have seen that many have used: shared numbervar total:=sum({tablename.ColumnName}); but i have used stored procedure instead of table so how could i find total of field that resultset returns from stored procedure.. plz give me answer as soon as possible.. i need it urgently. thanks..

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• How would I code a complex formula parser manually?

  - by StormianRootSolver

  Hm, this is language - agnostic, I would prefer doing it in C# or F#, but I'm more interested this time in the question "how would that work anyway". What I want to accomplish ist: a) I want to LEARN it - it's about my ego this time, it's for a fun project where I want to show myself that I'm a really good at this stuff b) I know a tiny little bit about EBNF (although I don't know yet, how operator precedence works in EBNF - Irony.NET does it right, I checked the examples, but this is a bit ominous to me) c) My parser should be able to take this: 5 * (3 + (2 - 9 * (5 / 7)) + 9) for example and give me the right results d) To be quite frankly, this seems to be the biggest problem in writing a compiler or even an interpreter for me. I would have no problem generating even 64 bit assembler code (I CAN write assembler manually), but the formula parser... e) Another thought: even simple computers (like my old Sharp 1246S with only about 2kB of RAM) can do that... it can't be THAT hard, right? And even very, very old programming languages have formula evaluation... BASIC is from 1964 and they already could calculate the kind of formula I presented as an example f) A few ideas, a few inspirations would be really enough - I just have no clue how to do operator precedence and the parentheses - I DO, however, know that it involves an AST and that many people use a stack So, what do you think?

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• Boost Binary Endian parser not working?

  - by Hai

  I am studying how to use boost spirit Qi binary endian parser. I write a small test parser program according to here and basics examples, but it doesn't work proper. It gave me the msg:"Error:no match". Here is my code. #include "boost/spirit/include/qi.hpp" #include "boost/spirit/include/phoenix_core.hpp" #include "boost/spirit/include/phoenix_operator.hpp" #include "boost/spirit/include/qi_binary.hpp" // parsing binary data in various endianness template '<'typename P, typename T void binary_parser( char const* input, P const& endian_word_type, T& voxel, bool full_match = true) { using boost::spirit::qi::parse; char const* f(input); char const* l(f + strlen(f)); bool result1 = parse(f,l,endian_word_type,voxel); bool result2 =((!full_match) || (f ==l)); if ( result1 && result2) { //doing nothing, parsing data is pass to voxel alreay } else { std::cerr << "Error: not match!!" << std::endl; exit(1); } } typedef boost::uint16_t bs_int16; typedef boost::uint32_t bs_int32; int main ( int argc, char *argv[] ) { namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; using qi::big_word; using qi::big_dword; boost::uint32_t ui; float uf; binary_parser("\x01\x02\x03\x04",big_word,ui); assert(ui=0x01020304); binary_parser("\x01\x02\x03\x04",big_word,uf); assert(uf=0x01020304); return 0; }' I almost copy the example, but why this binary parser doesn't work. I use Mac OS 10.5.8 and gcc 4.01 compiler.

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• How do you prevent Git from printing 'remote:' on each line of the output of a post-recieve hook?

  - by Matt Hodan

  I recently configured an EC2 instance with a Git deployment workflow that resembles Heroku, but I can't seem to figure out how Heroku prevents the Git post-receive hook from outputting 'remote:' on each line. Consider the following two examples (one from my EC2 project and one from a Heroku project): My EC2 project: git push prod master Counting objects: 9, done. Delta compression using up to 2 threads. Compressing objects: 100% (5/5), done. Writing objects: 100% (5/5), 456 bytes, done. Total 5 (delta 3), reused 0 (delta 0) remote: remote: Receiving push remote: Deploying updated files (by resetting HEAD) remote: HEAD is now at bf17da8 test commit remote: Running bundler to install gem dependencies remote: Fetching source index for http://rubygems.org/ remote: Installing rake (0.8.7) remote: Installing abstract (1.0.0) ... remote: Installing railties (3.0.0) remote: Installing rails (3.0.0) remote: Your bundle is complete! It was installed into ./.bundle/gems remote: Launching (by restarting Passenger)... done remote: To ssh://[email protected]/~/apps/app_name e8bd06f..bf17da8 master -> master Heroku: $> git push heroku master Counting objects: 179, done. Delta compression using up to 2 threads. Compressing objects: 100% (89/89), done. Writing objects: 100% (105/105), 42.70 KiB, done. Total 105 (delta 53), reused 0 (delta 0) -----> Heroku receiving push -----> Rails app detected -----> Gemfile detected, running Bundler version 1.0.3 Unresolved dependencies detected; Installing... Using --without development:test Fetching source index for http://rubygems.org/ Installing rake (0.8.7) Installing abstract (1.0.0) ... Installing railties (3.0.0) Installing rails (3.0.0) Your bundle is complete! It was installed into ./.bundle/gems Compiled slug size is 4.8MB -----> Launching... done http://your_app_name.heroku.com deployed to Heroku To [email protected]:your_app_name.git 3bf6e8d..642f01a master -> master

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• Designing small comparable objects

  - by Thomas Ahle

  Intro Consider you have a list of key/value pairs: (0,a) (1,b) (2,c) You have a function, that inserts a new value between two current pairs, and you need to give it a key that keeps the order: (0,a) (0.5,z) (1,b) (2,c) Here the new key was chosen as the average between the average of keys of the bounding pairs. The problem is, that you list may have milions of inserts. If these inserts are all put close to each other, you may end up with keys such to 2^(-1000000), which are not easily storagable in any standard nor special number class. The problem How can you design a system for generating keys that: Gives the correct result (larger/smaller than) when compared to all the rest of the keys. Takes up only O(logn) memory (where n is the number of items in the list). My tries First I tried different number classes. Like fractions and even polynomium, but I could always find examples where the key size would grow linear with the number of inserts. Then I thought about saving pointers to a number of other keys, and saving the lower/greater than relationship, but that would always require at least O(sqrt) memory and time for comparison. Extra info: Ideally the algorithm shouldn't break when pairs are deleted from the list.

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• Learning C++ as a Perl programmer

  - by meneldor

  Hello all, I'm a Perl5 programmer for 7 years and I'm trying to learn C++ now. Some of the c++ syntax is hard for me to understand and to think in c++ way. For example: In perl you can mix the data in the arrays @array = (1,"string",5.355); You can assign any value to a scalar variable: $var = 1; $var = "string"; $var = \$reference_to_scalar; There are many examples. The friend of mine recommend me the book "Thinking of C++" by Bruce Eckel, but I haven't any C background and it's hard for me to understand some things. So my question is - could you recommend me a book for this situation. I don't want to learn C. I understand OOP (I'm getting more familiar with C++ oop aswell), I understand the point of the pointers(and some arithmetic) and references(widely used in perl). I dont need some of the manuals for dummies (what is int,bool,double,if,while), I just need a direction how to learn C++ from my point of perl programmer, because I,m sure that there are many like me. Thank you in advance.

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• How do I add mouseClicked event to a swing table?

  - by Ayelet

  Hi, I am a new, terribly green user of Swing. I managed to create a table class using examples from java.sun tutorials, and I managed to load data dynamically into it. I want to be able to react to a click on a row by displaying a dialog box. How do I add the event Handler that will identify the selected row number? The main function code: public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { try { MainWindow window = new MainWindow(); window.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. createAndShowGUI(); //... and: private static void createAndShowGUI() { //Create and set up the window. JFrame frame = new JFrame("Data Table"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up data of the content pane. TableClass mainTable = new TableClass(fh.getColNames(), fh.getTableContent()); mainTable.setOpaque(true); frame.setContentPane(mainTable); //Display the window. frame.pack(); frame.setVisible(true); } Thank you

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• Is the size of a struct required to be an exact multiple of the alignment of that struct?

  - by Steve314

  Once again, I'm questioning a longstanding belief. Until today, I believed that the alignment of the following struct would normally be 4 and the size would normally be 5... struct example { int m_Assume_32_Bits; char m_Assume_8_Bit_Bytes; }; Because of this assumption, I have data structure code that uses offsetof to determine the distance in bytes between two adjacent items in an array. Today, I spotted some old code that was using sizeof where it shouldn't, couldn't understand why I hadn't had bugs from it, coded up a unit test - and the test surprised me by passing. A bit of investigation showed that the sizeof the type I used for the test (similar to the struct above) was an exact multiple of the alignment - ie 8 bytes. It had padding after the final member. Here is an example of why I never expected this... struct example2 { example m_Example; char m_Why_Cant_This_Be_At_Offset_6_Bytes; }; A bit of Googling showed examples that make it clear that this padding after the final member is allowed - for example http://en.wikipedia.org/wiki/Data_structure_alignment#Data_structure_padding (the "or at the end of the structure" bit). This is a bit embarrassing, as I recently posted this comment - Use of struct padding (my first comment to that answer). What I can't seem to determine is whether this padding to an exact multiple of the alignment is guaranteed by the C++ standard, or whether it is just something that is permitted and that some (but maybe not all) compilers do. So - is the size of a struct required to be an exact multiple of the alignment of that struct according to the C++ standard? If the C standard makes different guarantees, I'm interested in that too, but the focus is on C++.

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• asp.net vb user control raising an event on the calling page

  - by jvcoach23

  i'm trying to learn about user controls. I created a user control that has a textbox and a button. What i'd like to be able to do is when i click the button in the user control, populate a label in the aspx page. I understand that i could just have a button on the page that uses some properties on the user control to get that information.. but i'd like to know how to do it with the button the user control.. the reason for this is the button is just an example.. a learning tool. if i can get this working, i'd likely be putting thing in the user control that might require this kind of passing information. Anyway.. i've found some c# examples that i tried to get working as vb.. but once started getting into the delegates and events.. well.. it made me turn to this post. anyway.. hopefully someone can lend a hand.

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• read the currency format

  - by user485783

  perhaps for some people this is easy, but I want to learn There are 2 currency formats: first currency format is 1,123,123.12 and this format may be like $1,123,123.12 or 1,123,123.12€ and second currency format is 1.123.123,12 and this may be such $1.123.123,12 or 1.123.123,12€ so the difference is the placement of dots and commas The above format will be $this->value('one of the currency format insert here'); e.g. $this->value('$1,123,123.12'); or $this->value('1.123.123,12€'); that I want to know is the code if (first currency format) {use blah .. blah ..} elseif (second currency format) {use blah .. blah ..} else {/ / unsupported format} so how the code to identify whether the entry is input the first currency format or second currency format? thanks for the your pointers and ideas. UPDATED: I apologize for mistake in giving examples When I tried to test the code I have a little confused because it seems not working then I changed my prevoious parts, so that $value['amount'] it may be use first currency format 1,123,123.12 and this format may be like $1,123,123.12 or 1,123,123.12€ and second currency format 1.123.123,12 and this may be such $1.123.123,12 or 1.123.123,12€ then the value['amount'] will identify first with code like the following conditional class curr_format { private bla...bla..1 private bla...bla..2 var etc.. public function curr_format ($bla...,$and_bla..) { //then make conditional is here if (first currency format) {//use blah .. blah ..} elseif (second currency format) {//use blah .. blah ..} else {/ / unsupported format} //another codes.. at the end output as look like: $identify = new curr_format(); echo $identify->curr_format($value['amount'],$else_statement);

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• Texture2D.Bounds.Intersect, but the Bounds never move? - XNA, .Net 4.0

  - by Gineer

  Hi all, I am still shiny new to XNA, so please forgive any stupid question and statements in this post (The added issue is that I am using Visual Studio 2010 with .Net 4.0 which also means very few examples exist out on the web - well, none that I could find easily): I have two 2D objects in a "game" that I am using to learn more about XNA. I need to figure out when these two objects intersect. I noticed that the Texture2D objects has a property named "Bounds" which in turn has a method named "Intersects" which takes a Rectangle (the other Texture2D.Bounds) as an argument. However when you run the code, the objects always intersect even if they are on separate sides of the screen. When I step into the code, I noticed that for the Texture2D Bounds I get 4 parameters back when you mouse over the Bounds and the X, and Y coordinates always read "X = 0, Y = 0" for both objects (hence they always intersect). The thing that confuses me is the fact that the Bounds property is on the Texture rather than on the Position (or Vector2) of the objects. I eventually created a little helper method that takes in the objects and there positions and then calculate whether they intersect, but I'm sure there must be a better way. any suggestions, pointers would be much appreciated. Gineer

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• SWIG interface to receive an opaque struct reference in Java through function argument

  - by Beeo

  I am trying to use SWIG in order to use the Spotify API (libspotify) for Android: https://developer.spotify.com/technologies/libspotify/ I am having trouble defining the SWIG interface file to be able to successfully call the following native C function: sp_error sp_session_create(const sp_session_config * config, sp_session ** sess); Which in C would be called like this: //config struct defined previously sp_session *sess; sp_session_create(&config, &sess); But in Java I would need to call it like this: //config object defined previously sp_session javaSess = new sp_session(); sp_session_create(config, javaSess); sp_session is an opaque struct and is only defined in libspotify's API.h file as: typedef struct sp_session sp_session; I'm expecting the libspotify library to create it and give me a reference to it. The only thing I need that reference for then is to pass to other functions in the API. I believe the answer lies within the SWIG interface and typemaps, but I have been unsuccessful in trying to apply the examples I found in the documentation: http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_struct_pointer_pointer `http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_using_typemaps_return_arguments Help!

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• Why are compilers so stupid?

  - by martinus

  I always wonder why compilers can't figure out simple things that are obvious to the human eye. They do lots of simple optimizations, but never something even a little bit complex. For example, this code takes about 6 seconds on my computer to print the value zero (using java 1.6): int x = 0; for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) { x += x + x + x + x + x; } System.out.println(x); It is totally obvious that x is never changed so no matter how often you add 0 to itself it stays zero. So the compiler could in theory replace this with System.out.println(0). Or even better, this takes 23 seconds: public int slow() { String s = "x"; for (int i = 0; i < 100000; ++i) { s += "x"; } return 10; } First the compiler could notice that I am actually creating a string s of 100000 "x" so it could automatically use s StringBuilder instead, or even better directly replace it with the resulting string as it is always the same. Second, It does not recognize that I do not actually use the string at all, so the whole loop could be discarded! Why, after so much manpower is going into fast compilers, are they still so relatively dumb? EDIT: Of course these are stupid examples that should never be used anywhere. But whenever I have to rewrite a beautiful and very readable code into something unreadable so that the compiler is happy and produces fast code, I wonder why compilers or some other automated tool can't do this work for me.

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• How do I call an Obj-C method from Javascript?

  - by gnfti

  Hi all, I'm developing a native iPhone app using Phonegap, so everything is done in HTML and JS. I am using the Flurry SDK for analytics and want to use the [FlurryAPI logEvent:@"EVENT_NAME"]; method to track events. Is there a way to do this in Javascript? So when tracking a link I would imagine using something like <a onClick="flurryTrackEvent("Click_Rainbows")" href="#Rainbows">Rainbows</a> <a onClick="flurryTrackEvent("Click_Unicorns")" href="#Unicorns">Unicorns</a> "FlurryAPI.h" has the following: @interface FlurryAPI : NSObject { } + (void)startSession:(NSString *)apiKey; + (void)logEvent:(NSString *)eventName; + (void)logEvent:(NSString *)eventName withParameters:(NSDictionary *)parameters; + (void)logError:(NSString *)errorID message:(NSString *)message exception:(NSException *)exception; + (void)setUserID:(NSString *)userID; + (void)setEventLoggingEnabled:(BOOL)value; + (void)setServerURL:(NSString *)url; + (void)setSessionReportsOnCloseEnabled:(BOOL)sendSessionReportsOnClose; @end I'm only interested in the logEvent method(s). If it's not clear by now, I'm comfortable with JS but a recovering Obj-C noob. I've read the Apple docs but the examples described there are all for newly declared methods and I imagine this could be simpler to implement because the Obj-C method(s) are already defined. Thank you in advance for any input.

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• Learning libraries without books or tutorials

  - by Kawili-wili

  While many ask questions about where to find good books or tutorials, I'd like to take the opposite tack. I consider myself to be an entry-level programmer ready to move up to mid-level. I have written code in c, c++, c#, perl, python, clojure, vb, and java, so I'm not completely clueless. Where I see a problem in moving to the next level is learning to make better use of the literally hundreds upon hundreds of libraries available out there. I seem paralyzed unless there is a specific example in a book or tutorial to hand-hold me, yet I often read in various forums where another programmer attempts to assist with a question. He/she will look through the docs or scan the available classes/methods in their favorite IDE and seem to grok what's going on in a relatively short period of time, even if they had no previous experience with that specific library or function. I yearn to break the umbilical chord of constantly spending hour upon hour searching and reading, searching and reading, searching and reading. Many times there is no book or tutorial, or if there is, the discussion glosses over my specific needs or the examples shown are too far off the path for the usage I had in mind or the information is outdated and makes use of deprecated components or the library itself has fallen out of mainstream, yet is still perfectly usable (but no docs, books, or tutorials to hand-hold). My question is: In the absence of books or tutorials, what is the best way to grok new or unfamiliar libraries? I yearn to slicken the grok path so I can get down to the business of doing what I love most -- coding.

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• C++ Declarative Parsing Serialization

  - by Martin York

  Looking at Java and C# they manage to do some wicked processing based on special languaged based anotation (forgive me if that is the incorrect name). In C++ we have two problems with this: 1) There is no way to annotate a class with type information that is accessable at runtime. 2) Parsing the source to generate stuff is way to complex. But I was thinking that this could be done with some template meta-programming to achieve the same basic affect as anotations (still just thinking about it). Like char_traits that are specialised for the different types an xml_traits template could be used in a declaritive way. This traits class could be used to define how a class is serialised/deserialized by specializing the traits for the class you are trying to serialize. Example Thoughs: template<typename T> struct XML_traits { typedef XML_Empty Children; }; template<> struct XML_traits<Car> { typedef boost::mpl::vector<Body,Wheels,Engine> Children; }; template<typename T> std::ostream& Serialize(T const&) { // my template foo is not that strong. // but somthing like this. boost::mpl::for_each<typename XML_Traits<T>::Children,Serialize>(data); } template<> std::ostream& Serialize<XML_Empty>(T const&) { /* Do Nothing */ } My question is: Has anybody seen any projects/decumentation (not just XML) out there that uses techniques like this (template meta-programming) to emulate the concept of annotation used in languges like Java and C# that can then be used in code generation (to effectively automate the task by using a declaritive style). At this point in my research I am looking for more reading material and examples.

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• How do I connect to SQL Server with VB?

  - by Wayne Werner

  Hi, I'm trying to connect to a SQL server from VB. The SQL server is across the network uses my windows login for authentication. I can access the server using the following python code: import odbc conn = odbc.odbc('SignInspection') c = conn.cursor() c.execute("SELECT * FROM list_domain") c.fetchone() This code works fine, returning the first result of the SELECT. However, I've been trying to use the SqlClient.SqlConnection in VB, and it fails to connect. I've tried several different connection strings but this is the current code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim conn As New SqlClient.SqlConnection conn.ConnectionString = "data source=signinspection;initial catalog=signinspection;integrated security=SSPI" Try conn.Open() MessageBox.Show("Sweet Success") 'Insert some code here, woo Catch ex As Exception MessageBox.Show("Failed to connect to data source.") MessageBox.Show(ex.ToString()) Finally conn.Close() End Try End Sub It fails miserably, and it gives me an error that says "A network-related or instance-specific error occurred... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) I'm fairly certain it's my connection string, but nothing I've found has given me any solid examples (server=mySQLServer is not a solid example) of what I need to use. Thanks! -Wayne

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• Understanding how software testing works and what to test.

  - by RHaguiuda

  Intro: I've seen lots of topics here on SO about software testing and other terms I don't understand. Problem: As a beginner developer I, unfortunately, have no idea how software testing works, not even how to test a simple function. This is a shame, but thats the truth. I also hope this question can help others beginners developers too. Question: Can you help me to understand this subject a little bit more? Maybe some questions to start would help: When I develop a function, how should I test it? For example: when working with a sum function, should I test every input value possible or just some limits? How about testing functions with strings as parameters? In a big program, do I have to test every single piece of code of it? When you guys program do you test every code written? How automated test works and how can I try one? How tools for automated testing works and what they do? I`ve heard about unit testing. Can I have a brief explanation on this? What is a testing framework? If possible please post some code with examples to clarify the ideas. Any help on this topic is very welcome! Thanks.

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• Multiple jQuery.noConflict() instances...

  - by user353816

  I am working with several jQuery scripts that include a MenuFader (http://css-tricks.com/examples/MenuFader/), twitter feed, and timestamp. Additionally I have a couple Mootools scripts that include the Barackslideshow (http://devthought.com/wp-content/moogets/BarackSlideshow/demo.html). And finally I have a scrolling ticker with tooltips taken from the twitter homepage. I originally had a conflict with the Jquery MenuFader and Mootools BarackSlideshow, but easily fixed this issue with the jQuery.noconflict(); and replaced all corresponding $ with jQuery. Unfortunately, after I added the scrolling ticker from Twitter, the Mootools BarackSlideshow and the Jquery MenuFader no longer work. I tried to implement jQuery.noconflict(); then $.noconflict(); then var j = jQuery.noconflict(); and replacing the $ as I did previously, but I cannot get the scripts to play nicely. Any help is greatly appreciated...I have been working on this all day. I am pretty new with javascript, but have managed to get through most problems with a little persistence. Please take a look at the script below: <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.0/jquery.min.js" type="text/javascript"></script> <script src="http://a2.twimg.com/a/1274914417/javascripts/fronts.js" type="text/javascript"></script> <script type="text/javascript"> //<![CDATA[ $( function () { setTimeout(function() { $(".twtr-widget").append($("<div></div>").attr("class", "twtr-fade")); }, 0); (function() { var tabIndex = $("[tabindex]:last").attr("tabIndex"); var setTabIndex = function() { $(this).attr("tabindex", ++tabIndex); } $(".footer-nav a").each(setTabIndex); $(".language-select a").each(setTabIndex); })(); $("#signup_submit").scribe({ event_name: "signup_submit_click", experiment: "ab_signup_button", bucket: "sign_up" }, "www_ab_tests"); $('#signin_menu').isSigninMenu(); new FrontPage().init(); }); //]]>

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• What are the lengths/limits C preprocessor as a language creation tool? Where can I learn more about

  - by Weston C

  In his FAQ @ http://www2.research.att.com/~bs/bs_faq.html#bootstrapping, Bjarne Stroustrup says: To build [Cfront, the first C++ compiler], I first used C to write a "C with Classes"-to-C preprocessor. "C with Classes" was a C dialect that became the immediate ancestor to C++... I then wrote the first version of Cfront in "C with Classes". When I read this, it piqued my interest in the C preprocessor. I'd seen its macro capabilities as suitable for simplifying common expressions but hadn't thought about its ability to significantly add to syntax and semantics on the level that I imagine bringing classes to C took. So now I have a couple of questions on my mind: 1) Are there other examples of this approach to bootstrapping a language off of C? 2) Is the source to Stroustrup's original work available anywhere? 3) Where could I learn more about the specifics of utilizing this technique? 4) What are the lengths/limits of that approach? Could one, say, create a set of preprocessor macros that let someone write in something significantly Lisp/Scheme like?

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• What does it mean for an OS to "execute within user processes"? Do any modern OS's use that approach

  - by Chris Cooper

  I have recently become interested in operating system, and a friend of mine lent me a book called Operating Systems: Internals and Design Principles (I have the third edition), published in 1998. It's been a very interesting book so far, but I have come to the part dealing with process control, and it's using UNIX System V as one of its examples of an operating system that executes within user processes. This concept has struck me as a little strange. First of all, does this mean that OS instructions and data are stored in each user of the processes? Probably not, because that would be an absurdly redundant scheme. But if not, then what does it mean to "execute within" a user process? Do any modern operating systems use this approach? It seems much more logical to have the operating system execute as its own process, or even independently of all processes, if you're short on memory. All the inter-accessiblilty of process data required for this layout seems to greatly complicate things. (But maybe that's just because I don't quite get the concept ;D) Here is what the book says: "Execution within User Processes: An alternative that is common with operation systems on smaller machines is to execute virtually all operating system software in the context of a user process. ... "

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• Ant: use include and exclude together

  - by Ken

  OK, this seems like it should be really simple. I'm using Apache Ant 1.8, and I have a target which does: <delete file="output/program.tar.bz2"/> <tar basedir="input" destfile="output/program.tar.bz2" compression="bzip2"> <tarfileset dir="input"> <include name="goodfolder1/**"/> <include name="goodfolder2/**"/> <exclude name="**/badfile"/> <exclude name="**/*.badext"/> </tarfileset> </tar> I want it to make a .tar.bz2 of input/goodfolder1 and input/goodfolder2, excluding files named "badfile", and excluding files with extension ".badext". It's giving me a .tar.bz2, but it's including badfile and *.badext -- the excludes seem to be ignored. The order of include/exclude doesn't seem to make a difference. I tried wrapping the includes/excludes in a (the docs say it's implicit?), but it made no difference. I'm sure there's something simple I'm missing, since the manual has a very similar example, though in a somewhat different context. EDIT: It looks like it could be related to the dir="input" attribute: it's adding everything in "input", and then adding everything in the tarfileset to that. Files I want appear twice in the program.tar.bz2, but files that are excluded only appear once. But dir is mandatory, and I don't see how this is different from the examples in the manual.

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• Code Golf: Find the possible ways on a numpad

  - by ikar

  I was bored today at school and so I tried to amuse myself using my calculator and a "game" I've invented which isn't really a game but keeps the boringness away. Also some time has passed since the last real code-golf here, so I decided to create this one. Imagine a simplified numpad like you know it from your phone (I'll leave the 0 out for this code-golf as it kinda destroys all the fun) 1 2 3 4 5 6 7 8 9 Now the rules of the game were always: At the end every digit must have been visited exactly once You can start at any digit you want You can always move one digit up, down, left or right. You can't move diagonally! There a quite a lot of possible ways (or not; I haven't found out yet), here some trivial examples: > > v v < < > > | The output of the golf-program should look something like the above, I'll try to explain: Symbols: Go right < Go left ^ Go up v Go down | End of the way Example solutions: (Program output can either be the numbers pressed in the right order from beginning point to end, or an (ASCII) picture like above) 147852369 569874123 523698741 So if we speak out the example above it would be: Start at 1, move right to 2, move right to 3, go down to 6, go left to 5, go left to 4, go down to 7, go right to 8 then go right to 9 and we are finished! Now there are many different ways possible: You could as well start at 5 and go around it in a circle. So the task would be: Write a program that can compute (using brute-force or whatever) the possible solutions for the numpad problem described above. (Friendly rethorical question with smiley removed because it made some people think that this is homework)

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• Generics vs inheritance (when no collection classes are involved)

  - by Ram

  This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also validate the above statement. Can someone give a valid use of generics in a real-life scenario which does not involve any collections ? Pedantically, I was thinking about making an example which does not involve collections public class Animal<T> { public void Speak() { Console.WriteLine("I am an Animal and my type is " + typeof(T).ToString()); } public void Eat() { //Eat food } } public class Dog { public void WhoAmI() { Console.WriteLine(this.GetType().ToString()); } } and "An Animal of type Dog" will be Animal<Dog> magic = new Animal<Dog>(); It is entirely possible to have Dog getting inherited from Animal (Assuming a non-generic version of Animal)Dog:Animal Therefore Dog is an Animal Another example I was thinking was a BankAccount. It can be BankAccount<Checking>,BankAccount<Savings>. This can very well be Checking:BankAccount and Savings:BankAccount. Are there any best practices to determine if we should go with generics or with inheritance ?

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• Still Confused About Identifying vs. Non-Identifying Relationships

  - by Jason

  So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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