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• sqlite3 JOIN, GROUP_CONCAT using distinct with custom separator

  - by aiwilliams

  Given a table of "events" where each event may be associated with zero or more "speakers" and zero or more "terms", those records associated with the events through join tables, I need to produce a table of all events with a column in each row which represents the list of "speaker_names" and "term_names" associated with each event. However, when I run my query, I have duplication in the speaker_names and term_names values, since the join tables produce a row per association for each of the speakers and terms of the events: 1|Soccer|Bobby|Ball 2|Baseball|Bobby - Bobby - Bobby|Ball - Bat - Helmets 3|Football|Bobby - Jane - Bobby - Jane|Ball - Ball - Helmets - Helmets The group_concat aggregate function has the ability to use 'distinct', which removes the duplication, though sadly it does not support that alongside the custom separator, which I really need. I am left with these results: 1|Soccer|Bobby|Ball 2|Baseball|Bobby|Ball,Bat,Helmets 3|Football|Bobby,Jane|Ball,Helmets My question is this: Is there a way I can form the query or change the data structures in order to get my desired results? Keep in mind this is a sqlite3 query I need, and I cannot add custom C aggregate functions, as this is for an Android deployment. I have created a gist which makes it easy for you to test a possible solution: https://gist.github.com/4072840

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• Toggle row visibility one at a time

  - by kuswantin

  I have a couple of tables with similar structures like this: <table> <tbody> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> ..etc --- The fake button is added here <div class="addrow">Add another</div> </tbody> </table> Since this is a long list, I have a need to toggle the rows one at a time. I just need to show the first row, of course, the rest should be toggled. The action is when I click a dynamic fake button, it will show row no. 2, and clicking again will show another next row. This is what I have done so far: $("table#field_fruit_values tr.draggable").not(':first').hide(); $("table#field_vegetables_values tr.draggable").not(':first').hide(); $("body.form table.content-multiple-table tbody").append('<div class="addrow">Add</div>'); $(".addrow").click(function() { var hiddenRow = $(this).prev('tr.draggable'); $(this).prev(hiddenRow + 1).show(); //if (hiddenRow + ':last').length) { // <= silly logic // $(this).hide(); //} }); The button only works for one row. I must have done something wrong :) When the final is reached, I also want the button to disappear. Sorry if this question sound silly. Any help would be very much appreciated. Thanks.

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• Linking the Linker script file to source code

  - by user304097

  Hello , I am new to GNU compiler. I have a C source code file which contains some structures and variables in which I need to place certain variables at a particular locations. So, I have written a linker script file and used the __ attribute__("SECTION") at variable declaration, in C source code. I am using a GNU compiler (cygwin) to compile the source code and creating a .hex file using -objcopy option, but I am not getting how to link my linker script file at compilation to relocate the variables accordingly. I am attaching the linker script file and the C source file for the reference. Please help me link the linker script file to my source code, while creating the .hex file using GNU. /*linker script file*/ /*defining memory regions*/ MEMORY { base_table_ram : org = 0x00700000, len = 0x00000100 /*base table area for BASE table*/ mem2 : org =0x00800200, len = 0x00000300 /* other structure variables*/ } /*Sections directive definitions*/ SECTIONS { BASE_TABLE : { } > base_table_ram GROUP : { .text : { } { *(SEG_HEADER) } .data : { } { *(SEG_HEADER) } .bss : { } { *(SEG_HEADER) } } > mem2 } C source code: const UINT8 un8_Offset_1 __attribute__((section("BASE_TABLE"))) = 0x1A; const UINT8 un8_Offset_2 __attribute__((section("BASE_TABLE"))) = 0x2A; const UINT8 un8_Offset_3 __attribute__((section("BASE_TABLE"))) = 0x3A; const UINT8 un8_Offset_4 __attribute__((section("BASE_TABLE"))) = 0x4A; const UINT8 un8_Offset_5 __attribute__((section("BASE_TABLE"))) = 0x5A; const UINT8 un8_Offset_6 __attribute__((section("SEG_HEADER"))) = 0x6A; My intention is to place the variables of section "BASE_TABLE" at the address defined i the linker script file and the remaining variables at the "SEG_HEADER" defined in the linker script file above. But after compilation when I look in to the .hex file the different section variables are located in different hex records, located at an address of 0x00, not the one given in linker script file . Please help me in linking the linker script file to source code. Are there any command line options to link the linker script file, if any plese provide me with the info how to use the options. Thanks in advance, SureshDN.

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• Match entities fulfilling filter (strict superset of search)

  - by Jon

  I have an entity (let's say Person) with a set of arbitrary attributes with a known subset of values. I need to search for all of these entities that match all my filter conditions. That is, given a set of Attributes A, I need to find all people that have a set of Attributes that are a superset of A. For example, my table structures look like this: Person: id | name 1 | John Doe 2 | Jane Roe 3 | John Smith Attribute: id | attr_name 1 | Sex 2 | Eye Color ValidValue: id | attr_id | value_name 1 | 1 | Male 2 | 1 | Female 3 | 2 | Blue 4 | 2 | Green 5 | 2 | Brown PersonAttributes id | person_id | attr_id | value_id 1 | 1 | 1 | 1 2 | 1 | 2 | 3 3 | 2 | 1 | 2 4 | 2 | 2 | 4 5 | 3 | 1 | 1 6 | 3 | 2 | 4 In JPA, I have entities built for all of these tables. What I'd like to do is perform a search for all entities matching a given set of attribute-value pairs. For instance, I'd like to be able to find all males (John Doe and John Smith), all people with green eyes (Jane Roe or John Smith), or all females with green eyes (Jane Roe). I see that I can already take advantage of the fact that I only really need to match on value_id, since that's already unique and tied to the attr_id. But where can I go from there? I've been trying to do something like the following, given that the ValidValue is unique in all cases: select distinct p from Person p join p.personAttributes a where a.value IN (:values) Then I've tried putting my set of required values in as "values", but that gives me errors no matter how I try to structure that. I also have to get a little more complicated, as follows, but at this point I'd be happy with solving the first problem cleanly. However, if it's possible, the Attribute table actually has a field for default value: id | attr_name | default_value 1 | Sex | 1 2 | Eye Color | 5 If the value you're searching on happens to be the default value, I want it to return any people that have no explicit value set for that attribute, because in the application logic, that means they inherit the default value. Again, I'm more concerned about the primary question, but if someone who can help with that also has some idea of how to do this one, I'd be extremely grateful.

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• How can I use R (Rcurl/XML packages ?!) to scrap this webpage ?

  - by Tal Galili

  Hi all, I have a (somewhat complex) webscraping challenge that I wish to accomplish and would love for some direction (to whatever level you feel like sharing) here goes: I would like to go through all the "species pages" present in this link: http://gtrnadb.ucsc.edu/ So for each of them I will go to: The species page link (for example: http://gtrnadb.ucsc.edu/Aero_pern/) And then to the "Secondary Structures" page link (for example: http://gtrnadb.ucsc.edu/Aero_pern/Aero_pern-structs.html) Inside that link I wish to scrap the data in the page so that I will have a long list containing this data (for example): chr.trna3 (1-77) Length: 77 bp Type: Ala Anticodon: CGC at 35-37 (35-37) Score: 93.45 Seq: GGGCCGGTAGCTCAGCCtGGAAGAGCGCCGCCCTCGCACGGCGGAGGcCCCGGGTTCAAATCCCGGCCGGTCCACCA Str: >>>>>>>..>>>>.........<<<<.>>>>>.......<<<<<.....>>>>>.......<<<<<<<<<<<<.... Where each line will have it's own list (inside the list for each "trna" inside the list for each animal) I remember coming across the packages Rcurl and XML (in R) that can allow for such a task. But I don't know how to use them. So what I would love to have is: 1. Some suggestion on how to build such a code. 2. And recommendation for how to learn the knowledge needed for performing such a task. Thanks for any help, Tal

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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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• What is the general feeling about reflection extensions in std::type_info?

  - by Evan Teran

  I've noticed that reflection is one feature that developers from other languages find very lacking in c++. For certain applications I can really see why! It is so much easier to write things like an IDE's auto-complete if you had reflection. And certainly serialization APIs would be a world easier if we had it. On the other side, one of the main tenets of c++ is don't pay for what you don't use. Which makes complete sense. That's something I love about c++. But it occurred to me there could be a compromise. Why don't compilers add extensions to the std::type_info structure? There would be no runtime overhead. The binary could end up being larger, but this could be a simple compiler switch to enable/disable and to be honest, if you are really concerned about the space savings, you'll likely disable exceptions and RTTI anyway. Some people cite issues with templates, but the compiler happily generates std::type_info structures for template types already. I can imagine a g++ switch like -fenable-typeinfo-reflection which could become very popular (and mainstream libs like boost/Qt/etc could easily have a check to generate code which uses it if there, in which case the end user would benefit with no more cost than flipping a switch). I don't find this unreasonable since large portable libraries like this already depend on compiler extensions. So why isn't this more common? I imagine that I'm missing something, what are the technical issues with this?

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• "Work stealing" vs. "Work shrugging"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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• How do I supply extra info to IApplicationSettingsProvider class?

  - by joebeazelman

  Perhaps this question has been asked before in a different way, but I haven’t been able to find it. I have one or more plugin adapter assemblies in my application all having the type IPlugin, for instance. Each adapter has its own settings structures stored in a common directory. Whether they are stored in one contiguous file or in separate ones doesn’t matter. Each adapter can have one or more settings associated with it. The settings will have both a name and the Plugin it will be used for. How would I create such a configuration system using the following requirements: I want to use .NETs built in settings system and avoid writing one from scratch The host application will be responsible for locating the plugin settings and passing it to the plugin Each plugin will be responsible for reading and writing its own settings to separate concerns. The host application should call Plugin.Save(thePath) and it does its thing. All settings are user scoped So far, I realize that I would need to write my own SettingsProvider, but the provider seems to work in isolation in that there’s no way to pass it parameters such as the path of the plugin directory and the name of the settings. All of the example code I've seen has the provider getting the data from the runtime environment.

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• Access ADP - For/Against?

  - by webworm

  I have been tasked with taking an Access 97 application and moving the back-end data to SQL Server while moving the front end to Access 2003 (using Access Data Projects). In the process of this migration the back-end data structures will be changed significantly to support new functionality. If I had my wish we would not be using Access as the front end. I think our application would be much better served by WinForms, WPF, or a web application. We have the time needed to properly plan a business logic layer and implement an excellent solution but powers above me want to stay with Access because that is what they are familiar with. What I could use help with is pros/cons of continuing down this path of Access development. What are some legitimate arguments for and against using Access 2003? Here is what I have come up with so far. Pro Access: Already own Access 2003 licenses Easy GUI development Reports look nice Against Access Having to use VBA (Visual Basic for Applications) ADO vs DAO. Didn't Microsoft change things from Access 2002 to Access 2003? Not tied to Access runtime Choice in front end (WPF, WinForms, even ASP.NET) Maintainability True separation of logic from UI not possible Does Microsoft still support Access ADP? Perhaps there are other issues I am not aware off both for and against Access for application development. I am trying to keep an open mind while at the same time trying to maintain my sanity. I have been using C# since .NET was released and the thought of going back to VBA for six months makes my head hurt. Especially when I feel I could offer so much more if allowed to develop with modern languages and tools?

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• Google Chrome Extension - Help needed

  - by Jim-Y

  Im new on Google Chrome Extensions coding, and i have some basic questions. I want to make a Chrome Extension, and the scheme is the following: -a popup window, containing buttons and result fields (popup.html) -when a button is clicked, i want to trigger an event, this event should connect to a webserver (i make the servlet too), and gather information from the server. (XMLHttpRequest()) -after that, i want my extension to load the gathered information into one of the result fields. Simple, isn't it? But i have several problems, right at the beginning:( I started developing with reading tutorials, but i have fog on the main structure of an extension. Now, i started an app, containing a popup.html, manifest.json ... In popup.html theres a result field, and a button <div id="extension_container"> <div id="header"> <p id="intro">Result here</p> <button type="button" id="button">Click Me!</button> </div> <!-- END header --> <div id="content"> </div> <!-- END content --> When button is clicked, i trigger an event, handeled with jquery, code here: <script> $(document).ready(function(){ $("#button").click(function(){ $("#intro").text("Hello, im added"); alert("Clicked"); }); }); </script> And here comes the problem, in popup.html this doesnt work, if i load it to Chrome, nothing happens. Otherwise, if i open popup.html in browser, not as an extension, everything works fine. So, i think i have basic misunderstandings on extension structures, starting with background pages, background javascript and so on.. :( Could anyone help me?

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• Define a swig interface file for generation of wrapper to every type from some header file

  - by Dmitriy Matveev

  Hi! We're using some C library in our Java project. Several years ago some other developer which has retired few years ago (as always) has created all the wrappers for us. The wrappers were generated by the swig, but the interface file is lost now. The basic idea of library and the wrappers for it is following: There only one function which returns pointer to some complex object. And there are wrapper for that function. The complex object is a tree-like structure with dozens of node kinds and types (C structures) used to represent them. There are hundreds of wrappers for every field of every type and we're trying to use them all. The library was updated some time ago and now there are some new data we unaware of which yet, but would like to use. This data is contained in some of the objects indirectly contained or referenced from the object created by the function we call (Some new fields and types were added). I know that I shouldn't make any changes to the wrappers by hand and should rather modify the interface, but as I already wrote it's missing. For now I only want to generate wrappers some few types which are added/changed and them to our old wrappers, but later I want to start creation of interface file which will define "what and how should be wrapped". All the definitions necessary for us are defined in single header file. Is it possible to tell swig to generate wrappers for every type in this header? If so, how can I write such interface file?

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• Which language should I use to program a GUI application?

  - by Roman

  I would like to write a GUI application for management of information (text documents). In more details, it should be similar to the TiddlyWiki. I would like to have there some good visual effects (like nice representation for three structures, which you can rotate, some sound). I also would like to include some communication via Internet (for sharing and collaboration). In should include some features of such applications as a web browser, word processor, Skype. Which programming language should I use? I like the idea of usage of JavaScripts (like TddlyWiki). The good thing about that, is that user should not install anything. They open a file in a browser and it works! The bad thing is that JavaScript cannot communicate via internet with other applications. I think the choice of the programming language, in my case, id conditioned by 2 things: What can be done with this programming language (which restrictions are there). How easy to program. I would like to have "block" which can do a lot of things (rather than to program then and, in this way, to "rediscover a bicycle") ADDED: I would like to make it platform independent.

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• C#: How to run NUnit from my code

  - by Flavio

  Hello, I'd like to use NUnit to run unit tests in my plug-in, but it needs to be run in the context of my application. To solve this, I was trying to develop a plug-in that runs NUnit, which in turn will execute my tests in the application's context. I didn't find a specific documentation on this subject so I dug a piece of information here and there and I came out with the following piece of code (which is similar to one I found here in StackOverflow): SimpleTestRunner runner = new SimpleTestRunner(); TestPackage package = new TestPackage( "Test" ); string loc = Assembly.GetExecutingAssembly().Location package.Assemblies.Add( loc ); if( runner.Load(package) ) { TestResult result = runner.Run( new NullListener() ); } The result variable says "has no TestFixture" although I know for sure it is there. In fact my test file contains two test. Using another approach I found, which is summarized by the following code: TestSuiteBuilder builder = new TestSuiteBuilder(); TestSuite testSuite = builder.Build( package ); // Run tests TestResult result = testSuite.Run( new NullListener(), NUnit.Core.TestFilter.Empty ); I saw nunit data structures with only 1 test and I had the same error. For sake of completeness, I am using the latest version of nunit, which is 2.5.5.10112. Does anyone know what I'm missing? A sample code would be appreciated. thanks

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• How to react when asked a question you already know during an interview

  - by DevNull

  The short story:- If you are asked a tough algorithmic/puzzle question during an interview, whose solution is already known to you, do you:- Honestly tell the interviewer that you know this question already? -- this could result in bursting the interviewer's ego and him increasing the complexity level of the subsequent questions. Do an Oscar deserving performance and act as if you are thinking and trying hard and slowly getting to the solution? -- depending on your acting skills, could majorly impress the interviewer making the rest of the interview easier. Long story:- OK, this question comes as a result of what happened to me in a recent telephonic interview that I gave - the interview was supposed to be all algorithmic. The interviewer started with an algorithmic question which I had luckily already seen here on Stackoverflow. The best solution to that problem is not very intuitive and is more of a you-get-it-if-you-know-it kind. Now, just to not disappoint the interviewer too much, I took a few seconds as if I was pondering on the problem and then blurted out the answer which I knew too well having read and admired it on SO already. But I guess that gave it away to the interviewer that I already knew this question and since then, he started asking me for more efficient solutions and I kept coming up with approaches (even if not correct or more efficient, but I did touch a lot of different data structures and algos) and he kept asking for more efficient solutions and generally seemed put off by my initial salvo which was unexpected. What should I have done? Cheers!

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• Have I taken a wrong path in programming by being excessively worried about code elegance and style?

  - by Ygam

  I am in a major stump right now. I am a BSIT graduate, but I only started actual programming less than a year ago. I observed that I have the following attitude in programming: I tend to be more of a purist, scorning unelegant approaches to solving problems using code I tend to look at anything in a large scale, planning everything before I start coding, either in simple flowcharts or complex UML charts I have a really strong impulse on refactoring my code, even if I miss deadlines or prolong development times I am obsessed with good directory structures, file naming conventions, class, method, and variable naming conventions I tend to always want to study something new, even, as I said, at the cost of missing deadlines I tend to see software development as something to engineer, to architect; that is, seeing how things relate to each other and how blocks of code can interact (I am a huge fan of loose coupling) i.e the OOP thinking I tend to combine OOP and procedural coding whenever I see fit I want my code to execute fast (thus the elegant approaches and refactoring) This bothers me because I see my colleagues doing much better the other way around (aside from the fact that they started programming since our first year in college). By the other way around I mean, they fire up coding, gets the job done much faster because they don't have to really look at how clean their codes are or how elegant their algorithms are, they don't bother with OOP however big their projects are, they mostly use web APIs, piece them together and voila! Working code! CLients are happy, they get paid fast, at the expense of a really unmaintainable or hard-to-read code that lacks structure and conventions, or slow executions of certain actions (which the common reasoning against would be that internet connections are much faster these days, hardware is more powerful). The excuse I often receive is clients don't care about how you write the code, but they do care about how long you deliver it. If it works then all is good. Now, did my "purist" approach to programming may have been the wrong way to start programming? Should I just dump these purist concepts and just code the hell up because I have seen it: clients don't really care how beautifully coded it is?

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• How to detect whether there is a specific member variable in class?

  - by Kirill V. Lyadvinsky

  For creating algorithm template function I need to know whether x or X (and y or Y) in class that is template argument. It may by useful when using my function for MFC CPoint class or GDI+ PointF class or some others. All of them use different x in them. My solution could be reduces to the following code: template<int> struct TT {typedef int type;}; template<class P> bool Check_x(P p, typename TT<sizeof(&P::x)>::type b = 0) { return true; } template<class P> bool Check_x(P p, typename TT<sizeof(&P::X)>::type b = 0) { return false; } struct P1 {int x; }; struct P2 {float X; }; // it also could be struct P3 {unknown_type X; }; int main() { P1 p1 = {1}; P2 p2 = {1}; Check_x(p1); // must return true Check_x(p2); // must return false return 0; } But it does not compile in Visual Studio, while compiling in the GNU C++. With Visual Studio I could use the following template: template<class P> bool Check_x(P p, typename TT<&P::x==&P::x>::type b = 0) { return true; } template<class P> bool Check_x(P p, typename TT<&P::X==&P::X>::type b = 0) { return false; } But it does not compile in GNU C++. Is there universal solution? UPD: Structures P1 and P2 here are only for example. There are could be any classes with unknown members.

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• Schema design: many to many plus additional one to many

  - by chrisj

  Hi, I have this scenario and I'm not sure exactly how it should be modeled in the database. The objects I'm trying to model are: teams, players, the team-player membership, and a list of fees due for each player on a given team. So, the fees depend on both the team and the player. So, my current approach is the following: **teams** id name **players** id name **team_players** id player_id team_id **team_player_fees** id team_players_id amount send_reminder_on Schema layout ERD In this schema, team_players is the junction table for teams and players. And the table team_player_fees has records that belong to records to the junction table. For example, playerA is on teamA and has the fees of $10 and $20 due in Aug and Feb. PlayerA is also on teamB and has the fees of $25 and $25 due in May and June. Each player/team combination can have a different set of fees. Questions: Are there better ways to handle such a scenario? Is there a term for this type of relationship? (so I can google it) Or know of any references with similar structures?

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• Make Ant's delete task fail when a directory exists and is not deleted but not when it doesn't exist

  - by Tim Visher

  I have tho following clean function in my build script and I'd like to know how I can improve it. <target name="clean" description="Clean output directories."> <!-- Must not fail on error because it fails if directories don't exist. Is there really no better way to do this? --> <delete includeEmptyDirs="true" failonerror="false"> <fileset dir="${main.build.directory}" /> <fileset dir="dist" /> <fileset dir="${documentation.build.directory}" /> <fileset dir="/build-testing" /> </delete> </target> Specifically regarding my comment, I'm unhappy with the fact that I can't run this on a fresh box because the directory structure hasn't been set up yet by the other targets. We run the build in such a way that it entirely recreates the structures necessary for testing and deployment every time to avoid stale class files and such. With the way that delete currently is set up, a failure to delete a file does not fail the build and I'd like it to. I don't want it to fail the build if the file doesn't exist though. If it doesn't exist then what I'm asking it to do has already happened. Thoughts?

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• Using game of life or other virtual environment for artificial (intelligence) life simulation? [clos

  - by Berlin Brown

  One of my interests in AI focuses not so much on data but more on biologic computing. This includes neural networks, mapping the brain, cellular-automata, virtual life and environments. Described below is an exciting project that includes develop a virtual environment for bots to evolve in. "Polyworld is a cross-platform (Linux, Mac OS X) program written by Larry Yaeger to evolve Artificial Intelligence through natural selection and evolutionary algorithms." http://en.wikipedia.org/wiki/Polyworld " Polyworld is a promising project for studying virtual life but it still is far from creating an "intelligent autonomous" agent. Here is my question, in theory, what parameters would you use create an AI environment? Possibly a brain environment? Possibly multiple self contained life organisms that have their own "brain" or life structures. I would like a create a spin on the game of life simulation. What if you have a 64x64 game of life grid. But instead of one grid, you might have N number of grids. The N number of grids are your "life force" If all of the game of life entities die in a particular grid then that entire grid dies. A group of "grids" makes up a life form. I don't have an immediate goal. First, I want to simulate an environment and visualize what is going on in the environment with OpenGL and see if there are any interesting properties to the environment. I then want to add "scarce resources" and see if the AI environment can manage resources adequately.

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• Precision of cos(atan2(y,x)) versus using complex <double>, C++

  - by Ivan

  Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

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• Brackets matching using BIT

  - by amit.codename13

  edit: I was trying to solve a spoj problem. Here is the link to the problem : http://spoj.pl/problems/BRCKTS I can think of two possible data structures for solving the problem one using segment tree and the other using a BIT. I have already implemented the solution using a segment tree. I have read about BIT but i can't figure out how to do a particular thing with it(which i have mentioned below) I am trying to check if brackets are balanced in a given string containing only ('s or )'s. I am using a BIT(Binary indexed tree) for solving the problem. The procedure i am following is as follows: I am taking an array of size equal to the number of characters in the string. I am assigning -1 for ) and 1 for ( to the corresponding array elements. Brackets are balanced in the string only if the following two conditions are true. The cumulative sum of the whole array is zero. Minimum cumulative sum is non negative. i.e the minimum of cumulative sums of all the prefixes of the array is non-negative. Checking condition 1 using a BIT is trivial. I am facing problem in checking condition 2.

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• populating one checkedlistbox with another (checkedlistbox)

  - by 8thWonder

  I am having difficulties populating a checkedlistbox (CLB) based on the selection(s) made in another. It should also be noted that I have a "Select All" checkbox at the top that checks/unchecks all of the items in the first CLB. Here's the code: Private Sub chkSelectAll_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkSelectAll.CheckedChanged For i As Integer = 0 To clb1.Items.Count - 1 clb1.SetItemChecked(i, chkSelectAll.Checked) Next End Sub Private Sub clb1_ItemCheck(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemCheckEventArgs) Handles clb1.ItemCheck Dim i As Integer = clb1.SelectedIndex For j As Integer = 0 To al_2.Count - 1 If i = -1 Then For k As Integer = 0 To al_2.Count - 1 If Not clb2.Contains(al_2(k).sDate) Then clb2.Items.Add(al_2(k).sDate) Else : k += 1 End If Next ElseIf (e.NewValue = CheckState.Checked And al_2(j).sName = al_1(i)) Then clb2.Items.Add(al_2(j).sDate) ElseIf (e.NewValue = CheckState.Unchecked And al_2(j).sName = al_1(i)) Then clbProdBkups.Items.Remove(al_2(j).sDate) End If Next End Sub The first CLB is populated with an arraylist of values on the button click event. Based on whatever is checked in the first CLB, corresponding values from an arraylist of structures should fill the second CLB. The following code partially works until the "Select All" checkbox is clicked at which point one of two things happens: If other values have been selected before "Select All" is checked, the second CLB is filled with the correct number of corresponding values BUT only those of the most recently selected item of the first CLB instead of all of corresponding values of all of the items that were not already selected. When "Select All" is unchecked, the most recently incorrect values are removed, everything in CLB 1 is unchecked but the values in CLB 2 that were selected before "Select All" was checked remain. If "Select All" is checked before anything else is selected, I get an "unable to cast object of type 'System.String' to type 'System.Windows.Forms.Control'" error that points to the following statement from the itemcheck event: If Not clb2.Contains(al_2(k).sDate) Then Any insights will be greatly appreciated. ~8th

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• Asymptotic runtime of list-to-tree function

  - by Deestan

  I have a merge function which takes time O(log n) to combine two trees into one, and a listToTree function which converts an initial list of elements to singleton trees and repeatedly calls merge on each successive pair of trees until only one tree remains. Function signatures and relevant implementations are as follows: merge :: Tree a -> Tree a -> Tree a --// O(log n) where n is size of input trees singleton :: a -> Tree a --// O(1) empty :: Tree a --// O(1) listToTree :: [a] -> Tree a --// Supposedly O(n) listToTree = listToTreeR . (map singleton) listToTreeR :: [Tree a] -> Tree a listToTreeR [] = empty listToTreeR (x:[]) = x listToTreeR xs = listToTreeR (mergePairs xs) mergePairs :: [Tree a] -> [Tree a] mergePairs [] = [] mergePairs (x:[]) = [x] mergePairs (x:y:xs) = merge x y : mergePairs xs This is a slightly simplified version of exercise 3.3 in Purely Functional Data Structures by Chris Okasaki. According to the exercise, I shall now show that listToTree takes O(n) time. Which I can't. :-( There are trivially ceil(log n) recursive calls to listToTreeR, meaning ceil(log n) calls to mergePairs. The running time of mergePairs is dependent on the length of the list, and the sizes of the trees. The length of the list is 2^h-1, and the sizes of the trees are log(n/(2^h)), where h=log n is the first recursive step, and h=1 is the last recursive step. Each call to mergePairs thus takes time (2^h-1) * log(n/(2^h)) I'm having trouble taking this analysis any further. Can anyone give me a hint in the right direction?

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• WPF View/ViewModels using Generics- how?

  - by Investor5555

  New to WPF, so please bear with me... Suppose I have 2 tables in SQL Thing OtherThing Both have the exact same fields: ID (int) Name (string) Description (string) IsActive (bit/bool) DateModified (DateTime) So, I want to create one Model (not two) and do something like this: BaseModel<T>() { public int ID {get;set;} ... } etc. (of course, using the INotifyPropertyChanged, just trying to keep the code simple). I want to be able to create a BaseView and BaseViewModel that would work with whatever model conforms to the Thing/OtherThing. I am really at a loss as to what to do here to make this generic, so I don't have to have a ThingView/ThingViewModel and a OtherThingView/OtherThingViewModel... It seems that this should be simple, but I cannot seem to figure it out. Does anyone have a code example where they could interchange various items from a dropdown list using one view, one ViewModel, and one base datamodel (and switching out the type from a dropdown)? For example, a combobox has 3 identical table structures for Thing OtherThing SomeThing and on selection changed, I want to pull the data from whatever table was selected, to be able to do standard CRUD operations on any of these 3 tables, without having to create concrete classes for each view/viewmodel.

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