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  • How can i design a DB where the user can define the fields and types of a detail table in a M-D rela

    - by Simon
    My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be.

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  • Find all A^x in a given range

    - by Austin Henley
    I need to find all monomials in the form AX that when evaluated falls within a range from m to n. It is safe to say that the base A is greater than 1, the power X is greater than 2, and only integers need to be used. For example, in the range 50 to 100, the solutions would be: 2^6 3^4 4^3 My first attempt to solve this was to brute force all combinations of A and X that make "sense." However this becomes too slow when used for very large numbers in a big range since these solutions are used in part of much more intensive processing. Here is the code: def monoSearch(min, max): base = 2 power = 3 while 1: while base**power < max: if base**power > min: print "Found " + repr(base) + "^" + repr(power) + " = " + repr(base**power) power = power + 1 base = base + 1 power = 3 if base**power > max: break I could remove one base**power by saving the value in a temporary variable but I don't think that would make a drastic effect. I also wondered if using logarithms would be better or if there was a closed form expression for this. I am open to any optimizations or alternatives to finding the solutions.

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  • one click, two 'click' event fired

    - by Toni Michel Caubet
    I just want to toggle some elements when a link is clicked: This is how i am trying (But i don't really think that it matters much for this question what's inside the event function callback): /* mostrar exceso de comentarios a peticion del usuario*/ $('.toggleComments').click(function(){ console.log('.toggleComments'); if($(this).parents('.helpContent').find('.commentHideble:visible').length > 0){ $(this).text('+ <?=get_texto_clave('show_old_comments')?>').removeClass('toggleCommentsActive').append(' ('+$(this).parents('.helpContent').find('.commentHideble:not:visible').length+'+)'); }else{ $(this).text('- <?=get_texto_clave('hide_old_comments')?>').addClass('toggleCommentsActive'); } $(this).parents('.helpContent').find('.commentHideble').slideToggle(100); }); I even tried a boolean but gave me same result /* mostrar exceso de comentarios a peticion del usuario*/ var ctoggle = false; $('.toggleComments').click(function(){ if(ctoggle == false){ ctoggle = true; console.log('.toggleComments'); if($(this).parents('.helpContent').find('.commentHideble:visible').length > 0){ $(this).text('+ <?=get_texto_clave('show_old_comments')?>').removeClass('toggleCommentsActive').append(' ('+$(this).parents('.helpContent').find('.commentHideble:not:visible').length+'+)'); }else{ $(this).text('- <?=get_texto_clave('hide_old_comments')?>').addClass('toggleCommentsActive'); } $(this).parents('.helpContent').find('.commentHideble').slideToggle(100); ctoggle = false; } }); Why the log is being fired twice by click?

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  • C# Linq Select Problem in Method Chain.

    - by Gnought
    Note that the _src inherit IQueryable<U> and V inherit new(); I wrote the following statement, there is no syntax error. IQueryable<V> a = from s in _src where (s.Right - 1 == s.Left) select new V(); But if i re-wrote it as follows, the Visual Studio editor complains an error in the "Select" IQueryable<V> d = _src.Where(s => s.Right - 1 == s.Left).Select(s=> new V()); The Error is: The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly. Candidates are: System.Collections.Generic.IEnumerable<V> Select<U,V>(this System.Collections.Generic.IEnumerable<U>, System.Func<U,V>) (in class Enumerable) System.Linq.IQueryable<V> Select<U,V>(this System.Linq.IQueryable<U>, System.Linq.Expressions.Expression<System.Func<U,V>>) (in class Queryable) Could anyone explain this phenomenon, and what the solution is to fix the error?

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  • capture text, including tags from string, and then reorder tags with text

    - by Brian
    I have the following text: abcdef<CONVERSION>abcabcabcabc<2007-01-12><name1><2007-01-12>abcabcabcabc<name2><2007-01-11>abcabcabcabc<name3><2007-02-12>abcabcabcabc<name4>abcabcabcabc<2007-03-12><name5><date>abcabcabcabc<name6> I need to use regular expressions in order to clean the above text: The basic extraction rule is: <2007-01-12>abcabcabcabc<name2> I have no problem extracting this pattern. My issue is that within th text I have malformed sequences: If the text doesn't start with a date, and end with a name my extraction fails. For example, the text above may have several mal formed sequences, such as: abcabcabcabc<2007-01-12><name1> Should be: <2007-01-12>abcabcabcabc<name1> Is it possible to have a regular expression that would clean the above, prior to extracting my consistent pattern. In short, i need to find all mal formed patterns, and then take the date tag and put it in front of it, as provided in the example above. Thanks.

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  • Problem Binding to a Brush Property in WPF

    - by Krisc
    Working in WPF, writing a custom user control. I am trying to change the background property of the Border element when I change the value of a property of the class. Right now I am working on simply binding it to a DP, though if there is a better way I am open to suggestions. Here is the XAML for the UserControl <UserControl x:Class="MyProject.MyControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:js="clr-namespace:MyProject" mc:Ignorable="d" x:Name="MyControlRootLayout" Background="Transparent" d:DesignHeight="300" d:DesignWidth="300" Cursor="Hand"> <Border x:Name="RootBorder" Background="{Binding Path=CoreBackground, ElementName=MyControlRootLayout}" > </Border> </UserControl> And the code... public partial class MyControl : UserControl { public static DependencyProperty IsSelectedProperty = DependencyProperty.Register("IsSelected", typeof(bool), typeof(MyControl)); public static DependencyProperty CoreBackgroundProperty = DependencyProperty.Register("CoreBackground", typeof(Brush), typeof(MyControl)); public MyControl() { CoreBackground = new SolidColorBrush(Color.FromArgb(0, 255, 245, 104)); InitializeComponent(); Margin = new Thickness(5); } public Brush CoreBackground { get { return (Brush)GetValue(CoreBackgroundProperty); } set { SetValue(CoreBackgroundProperty, value); } } public bool IsSelected { get { return (bool)GetValue(IsSelectedProperty); } private set { SetValue(IsSelectedProperty, value); } } } Instead, the background comes out as transparent.

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • Passing values for method

    - by Kasun
    I beginner for programming. So can you please show me how to pass values for your compile() method. class CL { private const string clexe = @"cl.exe"; private const string exe = "Test.exe", file = "test.cpp"; private string args; public CL(String[] args) { this.args = String.Join(" ", args); this.args += (args.Length > 0 ? " " : "") + "/Fe" + exe + " " + file; } public Boolean Compile(String content, ref string errors) { //remove any old copies if (File.Exists(exe)) File.Delete(exe); if (File.Exists(file)) File.Delete(file); File.WriteAllText(file, content); Process proc = new Process(); proc.StartInfo.UseShellExecute = false; proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.RedirectStandardError = true; proc.StartInfo.FileName = clexe; proc.StartInfo.Arguments = this.args; proc.StartInfo.CreateNoWindow = true; proc.Start(); //errors += proc.StandardError.ReadToEnd(); errors += proc.StandardOutput.ReadToEnd(); proc.WaitForExit(); bool success = File.Exists(exe); return success; } }

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  • Magento, 1 db field not saved

    - by david parloir
    Hi there, I have a problem with 1 field of the db. With this code: $expireMonth = Mage::getStoreConfig('points_options/config_points/expiration_period', Mage::app()->getStore()->getId()); if (!is_null($expireMonth) && ($expireMonth > 0)) { $expireDate = date("Y-m-d H:i:s", strtotime("+" . $expireMonth . " month")); } else { $expireDate = NULL; } //die($expireDate); //store in points history table $this->_pointsModel->setCustomerId($this->_customer->getId()) ->setOrdersId('welcome') ->setPointsPending($pointsForNewCustomer) ->setPointsComment(Mage::helper('points')->__('welcome points')) ->setDateAdded(date('Y-m-d H:i:s')) ->setPointsStatus(2)//confirmed ->setPointsType('WE') ->setStoreId(Mage::app()->getStore()->getId()) ->setExpireDate($expireDate) ->save(); every field is saved in the table, except for expire_date. If I uncoment the die($expireData), I see the correct value, something like 2012-01-13 13:21:12. The filed is defined as: `expire_date` datetime NULL Any thaughts? edit: the solution is: $expireDate = date("Y-m-d H:i:s", strtotime("+" . $expireMonth . " months")); check out the "s" in my strtotime expression

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  • Project Naming Convention Feedback Please

    - by Sam Striano
    I am creating a ASP.NET MVC 3 application using Entity Framework 4. I am using the Repository/Service Pattern and was looking for feedback. I currently have the following: MVC Application (GTG.dll) GTG GTG.Controllers GTG.ViewModels Business POCO's (GTG.Business.dll) This contains all business objects (Customer, Order, Invoice, etc...) EF Model/Repositories (GTG.Data.dll) GTG.Business (GTG.Context.tt) I used the Entity POCO Generator Templates. GTG.Data.Repositories Service Layer (GTG.Data.Services.dll) GTG.Data.Services - Contains all of the service objects, one per aggregate root. The following is a little sample code: Controller Namespace Controllers Public Class HomeController Inherits System.Web.Mvc.Controller Function Index() As ActionResult Return View(New Models.HomeViewModel) End Function End Class End Namespace Model Namespace Models Public Class HomeViewModel Private _Service As CustomerService Public Property Customers As List(Of Customer) Public Sub New() _Service = New CustomerService _Customers = _Service.GetCustomersByBusinessName("Striano") End Sub End Class End Namespace Service Public Class CustomerService Private _Repository As ICustomerRepository Public Sub New() _Repository = New CustomerRepository End Sub Function GetCustomerByID(ByVal ID As Integer) As Customer Return _Repository.GetByID(ID) End Function Function GetCustomersByBusinessName(ByVal Name As String) As List(Of Customer) Return _Repository.Query(Function(x) x.CompanyName.StartsWith(Name)).ToList End Function End Class Repository Namespace Data.Repositories Public Class CustomerRepository Implements ICustomerRepository Public Sub Add(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Add End Sub Public Sub Delete(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Business.Customer Implements IRepository(Of Business.Customer).GetByID Using db As New GTGContainer Return db.Customers.FirstOrDefault(Function(x) x.ID = ID) End Using End Function Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Business.Customer, Boolean))) As System.Linq.IQueryable(Of Business.Customer) Implements IRepository(Of Business.Customer).Query Using db As New GTGContainer Return db.Customers.Where(Predicate) End Using End Function Public Sub Save(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Save End Sub End Class End Namespace

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  • Showing a MKAnnotation for custom object

    - by Chamanhm
    I have a list of objects and each of those has a title, name, description, latitude, longitude and address. Is it possible to show this objects as MKAnnotations? I've been stuck with this for hours now. When I tried to make the objects have a CLLocationCoordinate2D I kept getting the error about latitude or longitude not being assignable. #import <Foundation/Foundation.h> #import <MapKit/MapKit.h> @interface Oficina : NSObject <MKMapViewDelegate> @property (nonatomic, readwrite) CLLocationCoordinate2D oficinaCoordinate; @property (nonatomic, strong) NSString *oficinaCiudad; @property (nonatomic, strong) NSString *oficinaEstado; @property (nonatomic, strong) NSString *oficinaTitulo; @property (nonatomic, strong) NSString *oficinaTelefono; @property (nonatomic, strong) NSString *oficinaLatitud; @property (nonatomic, strong) NSString *oficinaLongitud; @property (nonatomic, strong) NSString *oficinaID; @property (nonatomic, strong) NSString *oficinaDireccion; @property (nonatomic, strong) NSString *oficinaHorario; @property (nonatomic, strong) NSString *oficinaTipoDeOficina; @property (nonatomic, strong) NSString *oficinaServicios; @property (nonatomic, strong) NSString *oficinaTipoDeModulo; @end So after consuming an internet service I get around 70 of these objects. Now I want to be able to turn each of those into a map annotation. This is one of the ways I've tried to assign the latitude but I get the error "Expression not assignable".. currentOffice.oficinaCoordinate.latitude = [parseCharacters floatValue]; Where currentOffice is an instance of my custom object.

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  • displaying a physical webpage with frames in iframe

    - by ksa
    i have iframe in my webpage, i have done the coding part for browsing the folders and viewing files in iframe.each folder has a index.html.now i need to display the index.html in iframe.index.html page contains frames divided into 2,each from different sources.i tried to display a sample webpage without frames and it was a success,page with frames spoils the party. my code for getting the html file <% String path=request.getParameter("name"); File directory = new File(path); FileFilter fileFilter=new FileFilter() { @Override public boolean accept(File file) { return file.getName().endsWith("html"); } }; File[] files = directory.listFiles(fileFilter); for (int index = 0; index < files.length; index++) { String s= files[index].getName(); String s1=files[index].getAbsolutePath(); %> <a href="fileview?name=<%=s1%>" target="sss"><%=s%></a> <% } %> mycode for displaying the page in iframe. public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException,IOException { res.setContentType("text/html"); PrintWriter out=res.getWriter(); String name=req.getParameter("name"); res.setHeader("Content-Disposition", "inline; filename=\""+name+"\""); java.io.FileInputStream fis=new java.io.FileInputStream(name); int i; while((i=fis.read())!=-1) { out.write(i); } fis.close(); out.close(); }

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  • How do I add an object to a binary tree based on the value of a member variable?

    - by Max
    How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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  • Getting rejected value null spring validation

    - by Shabarinath
    Hi in my project when I am trying to validate my form its not showing any error messages even if validation fails (Event Form is not submitted and enters into validation fail block) Here is my code /****************** Post Method *************/ @RequestMapping(value="/property", method = RequestMethod.POST) public String saveOrUpdateProperty(@ModelAttribute("property") Property property, BindingResult result, Model model, HttpServletRequest request) throws Exception { try { if(validateFormData(property, result)) { model.addAttribute("property", new Property()); return "property/postProperty"; } } /********* Validate Block *************/ private boolean validateFormData(Property property, BindingResult result) throws DaoException { if (property.getPropertyType() == null || property.getPropertyType().equals("")) { result.rejectValue("propertyType", "Cannot Be Empty !", "Cannot Be Empty !"); } if (property.getTitle() == null || property.getTitle().equals("")) { result.rejectValue("title", "Cannot Be Empty !", "Cannot Be Empty !"); } return (result.hasFieldErrors() || result.hasErrors()); } But when i debug i can see below one org.springframework.validation.BeanPropertyBindingResult: 1 errors Field error in object 'property' on field 'title': rejected value [null]; codes [Cannot Be Empty !.property.title,Cannot Be Empty !.title,Cannot Be Empty !.java.lang.String,Cannot Be Empty !]; arguments []; default message [Cannot Be Empty !] and this is how i am displaying in jsp file <div class="control-group"> <div class="controls"> <label class="control-label"><span class="required">* </span>Property Type</label> <div class="controls"> <form:input path="title" placeholder="Pin Code" cssClass="form-control border-radius-4 textField"/> <form:errors path="title" style="color:red;"/> </div> </div> </div> Event though when i see the below one when i debug (1 Error its correct) org.springframework.validation.BeanPropertyBindingResult: 1 errors Why it is not displayed in jsp can any one hep me?

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  • SQL aggregate query question

    - by Phil
    Hi, Can anyone help me with a SQL query in Apache Derby SQL to get a "simple" count. Given a table ABC that looks like this... id a b c 1 1 1 1 2 1 1 2 3 2 1 3 4 2 1 1 ** 5 2 1 2 ** ** 6 2 2 1 ** 7 3 1 2 8 3 1 3 9 3 1 1 How can I write a query to get a count of how may distinct values of 'a' have both (b=1 and c=2) AND (b=2 and c=1) to get the correct result of 1. (the two rows marked match the criteria and both have a value of a=2, there is only 1 distinct value of a in this table that match the criteria) The tricky bit is that (b=1 and c=2) AND (b=2 and c=1) are obviously mutually exclusive when applied to a single row. .. so how do I apply that expression across multiple rows of distinct values for a? These queries are wrong but to illustrate what I'm trying to do... "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 AND b=2 AND c=1 ..." .. (0) no go as mutually exclusive "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 OR b=2 AND c=1 ..." .. (3) gets me the wrong result. SELECT COUNT(a) (CASE WHEN b=1 AND c=10 THEN 1 END) FROM ABC WHERE b=2 AND c=1 .. (0) no go as mutually exclusive Cheers, Phil.

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  • OnEditorActionListener called twice with same eventTime on SenseUI keyboard

    - by ydant
    On just one phone I am testing on (HTC Incredible, Android 2.2, Software 3.21.605.1), I am experiencing the following behavior. The onEditorAction event handler is being called twice (immediately) when the Enter key on the Sense UI keyboard is pressed. The KeyEvent.getEventTime() is the same for both times the event is called, leading me to this work-around: protected void onCreate(Bundle savedInstanceState) { [...] EditText text = (EditText)findViewById(R.id.txtBox); text.setOnEditorActionListener(new OnEditorActionListener() { private long lastCalled = -1; public boolean onEditorAction(TextView v, int actionId, KeyEvent event) { if ( event.getEventTime() == lastCalled ) { return false; } else { lastCalled = event.getEventTime(); handleNextButton(v); return true; } } }); [...] } The EditText is defined as: <EditText android:layout_width="150sp" android:layout_height="wrap_content" android:id="@+id/txtBox" android:imeOptions="actionNext" android:capitalize="characters" android:singleLine="true" android:inputType="textVisiblePassword|textCapCharacters|textNoSuggestions" android:autoText="false" android:editable="true" android:maxLength="6" /> On all other devices I've tested on, the action button is properly labeled "Next" and the event is only called a single time when that button is pressed. Is this a bug in Sense UI's keyboard, or am I doing something incorrectly? Thank you for any assistance.

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  • BlackBerry 5.0 causing full menu to show on navigationClick

    - by jwadsack
    I have a BlackBerry app that is built for 4.5.x SDK. The first page of the app shows a list of fields and each field can be highlighted and clicked. The click action shows a new view with additional information about the field. This all works fine in 4.5, 4.6 and 4.7 and on the sim with 5.0. On a real 9000 running 5.0, when clicking the trackball on an item in the list, the full menu is showing rather than the click event getting consumed (or even fired) for the field. The view is derived from MainScreen and looks something like this: public class ListView extends MainScreen { public ItemCollection list = new ItemCollection; protected void sublayout( int maxWidth, int maxHeight ) { int i = 1; while(( item == (Item)list.nextElement()) != null) { ItemField field = new ItemField(item, i++); add(field); } } } This class does not consume navigationClick, but shouldn't need to, right? The field class does consume navigationClick event: public class ItemField extends Field { protected boolean navigationClick(int status, int time) { controller.showDeal(item.id, Session.current); return true; } } Is there something that changed in 5.0 that I need to add to have this app work the same for all platforms?

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  • understanding and implementing Boids

    - by alphablender
    So I'm working on porting Boids to Brightscript, based on the pseudocode here: http://www.kfish.org/boids/pseudocode.html I'm trying to understand the data structures involved, for example is Velocity a single value, or is it a 3D value, ie velocity={x,y,z} It seems as if the pseudocode seems to mix this up where sometimes it has an equation that incudes both vectors and single-value items: v1 = rule1(b) v2 = rule2(b) v3 = rule3(b) b.velocity = b.velocity + v1 + v2 + v3 If Velocity is a tripartite value then this would make sense, but I'm not sure. So my first question here is, is this the correct datastructure for a single boid based on the Pseudocode on that page: boid={position:{px:0,py:0,pz:0},velocity:{x:0,y:0,z:0},vector:{x:0,y:0,z:0},pc:{x:0,y:0,z:0},pv:{x:0,y:0,z:0}) where pc=perceived center, pv= perceived velocity I"ve implemented a vector_add, vector_sub, vector_div, and vector boolean functions. The reason I'm starting from this pseudocode is I've not been able to find anything else that is as readable, but it still leaves me with lots of questions as the data structures are not explicitly defined for each variable. (edit) here's a good example of what i'm talking about: IF |b.position - bJ.position| < 100 THEN if b.position - b[j].position are both 3D coordinates, how can they be considered "less than 100" unless they are < {100,100,100} ? Maybe that is what I need to do here, use a vector comparison function?

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  • ReplaceAll not working as expected

    - by Tim Kemp
    Still early days with Mathematica so please forgive what is probably a very obvious question. I am trying to generate some parametric plots. I have: ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} No joy: the replacement rules are not applied and a, b and h remain undefined. If I instead do: Hold@ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} it looks like the rules ARE working, as confirmed by the output: Hold[ParametricPlot[{(2 + 1) Cos[t] - 1 Cos[(2 + 1) t], (2 + 1) Sin[t] - 1 Sin[(2 + 1) t]}, {t, 0, 2 \[Pi]}, PlotRange -> All]] Which is what I'd expect. Take the Hold off, though, and the ParametricPlot doesn't work. There's nothing wrong with the equations or the ParametricPlot itself, though, because I tried setting values for a, b and h in a separate expression (a=2; b=1; h=1) and I get my pretty double cardoid out as expected. So, what am I doing wrong with ReplaceAll and why are the transformation rules not working? This is another fundamentally important aspect of MMA that my OOP-ruined brain isn't understanding. I tried reading up on ReplaceAll and ParametricPlot and the closest clue I found was that "ParametricPlot has attribute HoldAll and evaluates f only after assigning specific numerical values to variables" which didn't help much or I wouldn't be here. Thanks.

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  • How to parse mathematical expressions involving parentheses

    - by Rob P.
    Please forgive my title, I really don't know how to phrase it better. This isn't a school assignment or anything, but I realize it's a mostly academic question. But, what I've been struggling to do is parse 'math' text and come up with an answer. For Example - I can figure out how to parse '5 + 5' or '3 * 5' - but I fail when I try to correctly chain operations together. (5 + 5) * 3 It's mostly just bugging me that I can't figure it out. If anyone can point me in a direction, I'd really appreciate it. EDIT Thanks for all of the quick responses. I'm sorry I didn't do a better job of explaining. First - I'm not using regular expressions. I also know there are already libraries available that will take, as a string, a mathematical expression and return the correct value. So, I'm mostly looking at this because, sadly, I don't "get it". Second - What I've tried doing (is probably misguided) but I was counting '(' and ')' and evaluating the deepest items first. In simple examples, this worked; but my code is not pretty and more complicated stuff crashes. When I 'calculated' the lowest level, I was modifying the string. So... (5 + 5) * 3 Would turn into 10 * 3 Which would then evaluate to 30 But it just felt 'wrong'. I hope that helps clarify things. I'll certainly check out the links provided.

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  • android: ending activity from tab

    - by Jin
    I have 3 classes, let's call them 1, 2, and 3. Class 1 extends TabActivity and organizes the whole tab thing, Class 2 and 3 are just two separate tabs each with some lines of text. I call Class 1 from another activity using startActivityForResult. I then added an optionsMenu in class 2, and when user clicks the optionMenu, the following code is carried out: @Override public boolean onMenuItemSelected(int featureId, MenuItem item) { Intent i = new Intent(); switch(item.getItemId()) { case Result.NEXT_ID: i.putExtra(Result.PAGE_REQUEST, NEXT); setResult(RESULT_OK, i); finish(); break; case Result.PREV_ID: i.putExtra(Result.PAGE_REQUEST, PREV); setResult(RESULT_OK, i); finish(); } return super.onMenuItemSelected(featureId, item); } In my parent class (the class that called 1 to begin with), in its onActivityResult function, I want to get the data from the extras. However, the intent is always null, and I can't figure out why. When I call finish() on class 2, is it calling some other function in class 1? Do I have to transfer the intent data somehow?

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  • How do I handle freeing unmanaged structures in C# on application close?

    - by LostKaleb
    I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } } Thanks in advance!

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  • Database Tutorial: The method open() is undefined for the type MainActivity.DBAdapter

    - by user2203633
    I am trying to do this database tutorial on SQLite Eclipse: https://www.youtube.com/watch?v=j-IV87qQ00M But I get a few errors at the end.. at db.ppen(); i get error: The method open() is undefined for the type MainActivity.DBAdapter and similar for insert record and close. MainActivity: package com.example.studentdatabase; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import android.app.Activity; import android.app.ListActivity; import android.content.Intent; import android.database.Cursor; import android.os.Bundle; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.Button; import android.widget.Toast; public class MainActivity extends Activity { /** Called when the activity is first created. */ //DBAdapter db = new DBAdapter(this); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button addBtn = (Button)findViewById(R.id.add); addBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent i = new Intent(MainActivity.this, addassignment.class); startActivity(i); } }); try { String destPath = "/data/data/" + getPackageName() + "/databases/AssignmentDB"; File f = new File(destPath); if (!f.exists()) { CopyDB( getBaseContext().getAssets().open("mydb"), new FileOutputStream(destPath)); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } DBAdapter db = new DBAdapter(); //---add an assignment--- db.open(); long id = db.insertRecord("Hello World", "2/18/2012", "DPR 224", "First Android Project"); id = db.insertRecord("Workbook Exercises", "3/1/2012", "MAT 100", "Do odd numbers"); db.close(); //---get all Records--- /* db.open(); Cursor c = db.getAllRecords(); if (c.moveToFirst()) { do { DisplayRecord(c); } while (c.moveToNext()); } db.close(); */ /* //---get a Record--- db.open(); Cursor c = db.getRecord(2); if (c.moveToFirst()) DisplayRecord(c); else Toast.makeText(this, "No Assignments found", Toast.LENGTH_LONG).show(); db.close(); */ //---update Record--- /* db.open(); if (db.updateRecord(1, "Hello Android", "2/19/2012", "DPR 224", "First Android Project")) Toast.makeText(this, "Update successful.", Toast.LENGTH_LONG).show(); else Toast.makeText(this, "Update failed.", Toast.LENGTH_LONG).show(); db.close(); */ /* //---delete a Record--- db.open(); if (db.deleteRecord(1)) Toast.makeText(this, "Delete successful.", Toast.LENGTH_LONG).show(); else Toast.makeText(this, "Delete failed.", Toast.LENGTH_LONG).show(); db.close(); */ } private class DBAdapter extends BaseAdapter { private LayoutInflater mInflater; //private ArrayList<> @Override public int getCount() { return 0; } @Override public Object getItem(int arg0) { return null; } @Override public long getItemId(int arg0) { return 0; } @Override public View getView(int arg0, View arg1, ViewGroup arg2) { return null; } } public void CopyDB(InputStream inputStream, OutputStream outputStream) throws IOException { //---copy 1K bytes at a time--- byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, length); } inputStream.close(); outputStream.close(); } public void DisplayRecord(Cursor c) { Toast.makeText(this, "id: " + c.getString(0) + "\n" + "Title: " + c.getString(1) + "\n" + "Due Date: " + c.getString(2), Toast.LENGTH_SHORT).show(); } public void addAssignment(View view) { Intent i = new Intent("com.pinchtapzoom.addassignment"); startActivity(i); Log.d("TAG", "Clicked"); } } DBAdapter code: package com.example.studentdatabase; public class DBAdapter { public static final String KEY_ROWID = "id"; public static final String KEY_TITLE = "title"; public static final String KEY_DUEDATE = "duedate"; public static final String KEY_COURSE = "course"; public static final String KEY_NOTES = "notes"; private static final String TAG = "DBAdapter"; private static final String DATABASE_NAME = "AssignmentsDB"; private static final String DATABASE_TABLE = "assignments"; private static final int DATABASE_VERSION = 2; private static final String DATABASE_CREATE = "create table if not exists assignments (id integer primary key autoincrement, " + "title VARCHAR not null, duedate date, course VARCHAR, notes VARCHAR );"; private final Context context; private DatabaseHelper DBHelper; private SQLiteDatabase db; public DBAdapter(Context ctx) { this.context = ctx; DBHelper = new DatabaseHelper(context); } private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { try { db.execSQL(DATABASE_CREATE); } catch (SQLException e) { e.printStackTrace(); } } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS contacts"); onCreate(db); } } //---opens the database--- public DBAdapter open() throws SQLException { db = DBHelper.getWritableDatabase(); return this; } //---closes the database--- public void close() { DBHelper.close(); } //---insert a record into the database--- public long insertRecord(String title, String duedate, String course, String notes) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_TITLE, title); initialValues.put(KEY_DUEDATE, duedate); initialValues.put(KEY_COURSE, course); initialValues.put(KEY_NOTES, notes); return db.insert(DATABASE_TABLE, null, initialValues); } //---deletes a particular record--- public boolean deleteContact(long rowId) { return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; } //---retrieves all the records--- public Cursor getAllRecords() { return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE, KEY_DUEDATE, KEY_COURSE, KEY_NOTES}, null, null, null, null, null); } //---retrieves a particular record--- public Cursor getRecord(long rowId) throws SQLException { Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE, KEY_DUEDATE, KEY_COURSE, KEY_NOTES}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } //---updates a record--- public boolean updateRecord(long rowId, String title, String duedate, String course, String notes) { ContentValues args = new ContentValues(); args.put(KEY_TITLE, title); args.put(KEY_DUEDATE, duedate); args.put(KEY_COURSE, course); args.put(KEY_NOTES, notes); return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } } addassignment code: package com.example.studentdatabase; public class addassignment extends Activity { DBAdapter db = new DBAdapter(this); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.add); } public void addAssignment(View v) { Log.d("test", "adding"); //get data from form EditText nameTxt = (EditText)findViewById(R.id.editTitle); EditText dateTxt = (EditText)findViewById(R.id.editDuedate); EditText courseTxt = (EditText)findViewById(R.id.editCourse); EditText notesTxt = (EditText)findViewById(R.id.editNotes); db.open(); long id = db.insertRecord(nameTxt.getText().toString(), dateTxt.getText().toString(), courseTxt.getText().toString(), notesTxt.getText().toString()); db.close(); nameTxt.setText(""); dateTxt.setText(""); courseTxt.setText(""); notesTxt.setText(""); Toast.makeText(addassignment.this,"Assignment Added", Toast.LENGTH_LONG).show(); } public void viewAssignments(View v) { Intent i = new Intent(this, MainActivity.class); startActivity(i); } } What is wrong here? Thanks in advance.

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  • Rails: update_attribute vs update_attributes

    - by Sam
    Object.update_attribute(:only_one_field, "Some Value") Object.update_attributes(:field1 => "value", :field2 => "value2", :field3 => "value3") Both of these will update an object without having to explicitly tell AR to update. Rails API says: for update_attribute Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default. for update_attributes Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned. So if I don't want to have the object validated I should use update_attribute. What if I have this update on a before_save, will it stackoverflow? My question is does update_attribute also bypass the before save or just the validation. Also, what is the correct syntax to pass a hash to update_attributes... check out my example at the top.

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  • IS operator behaving a bit strangely

    - by flockofcode
    1) According to my book, IS operator can check whether expression E (E is type) can be converted to the target type only if E is either a reference conversion, boxing or unboxing. Since in the following example IS doesn’t check for either of the three types of conversion, the code shouldn’t work, but it does: int i=100; if (i is long) //returns true, indicating that conversion is possible l = i; 2) a) B b; A a = new A(); if (a is B) b = (B)a; int i = b.l; class A { public int l = 100; } class B:A { } The above code always causes compile time error “Use of unassigned variable”. If condition a is B evaluates to false, then b won’t be assigned a value, but if condition is true, then it will. And thus by allowing such a code compiler would have no way of knowing whether the usage of b in code following the if statement is valid or not ( due to not knowing whether a is b evaluates to true or false) , but why should it know that? Intsead why couldn’t runtime handle this? b) But if instead we’re dealing with non reference types, then compiler doesn’t complain, even though the code is identical.Why? int i = 100; long l; if (i is long) l = i; thank you

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