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• Orbital equations, and power required to run them

  - by Adam Davis

  Due to a discussion on the SO IRC today, I'm curious about orbital mechanics, and The equations needed to solve orbital problems The computing power required to solve complex problems The question in particular is calculating when the Earth will plow into the Sun (or vice versa, depending on the frame of reference). I suspect that all the gravitational pulls within our solar system may need to be calculated, which makes me wonder what type of computer cluster is required, or can this be done on a single box? I don't have the experience to do a back of the napkin test here, but perhaps you do? Also, much thx to Gortok for the original inspiration (see comments).

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• Starting to construct a data access layer. Things to consider?

  - by Phil

  Our organisation uses inline sql. We have been tasked with providing a suitable data access layer and are weighing up the pro's and cons of which way to go... Datasets ADO.net Linq Entity framework Subsonic Other? Some tutorials and articles I have been using for reference: http://www.asp.net/(S(pdfrohu0ajmwt445fanvj2r3))/learn/data-access/tutorial-01-vb.aspx http://www.simple-talk.com/dotnet/.net-framework/designing-a-data-access-layer-in-linq-to-sql/ http://msdn.microsoft.com/en-us/magazine/cc188750.aspx http://msdn.microsoft.com/en-us/library/aa697427(VS.80).aspx http://www.subsonicproject.com/ I'm extremely torn, and finding it very difficult to make a decision on which way to go. Our site is a series of 2 internal portals and a public web site. We are using vs2008 sp1 and framework version 3.5. Please can you give me advise on what factors to consider and any pro's and cons you have faced with your data access layer. Thanks.

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• Creating an Extremely Large Index in Oracle

  - by Rudiger

  Can someone look at the linked reference and explain to me the precise statements to run? Oracle DBA's Guide: Creating a Large Index Here's what I came up with... CREATE TEMPORARY TABLESPACE ts_tmp TEMPFILE 'E:\temp01.dbf' SIZE 10000M REUSE AUTOEXTEND ON EXTENT MANAGEMENT LOCAL; ALTER USER me TEMPORARY TABLESPACE ts_tmp; CREATE UNIQUE INDEX big_table_idx ON big_table ( record_id ); DROP TABLESPACE ts_tmp; Edit 1 After this index was created, I ran an explain plan for a simple query and get this error: ORA-00959: tablespace 'TS_TMP' does not exist It seems like it's not temporary at all... :(

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• dynamically create sitemap xml using php

  - by rekhasathvika

  Hi, I have created sitemap for my site using some reference code in the below link http://stackoverflow.com/questions/2747801/creating-an-xml-sitemap-with-php But I am getting error as XML Parsing Error: undefined entity Location: as my content is as follows << alt attribute and it says something like < loc http://www.example.com/700- & laquo;alt & raquo;-attributes-in-images.php< /loc Can anyone tell me how to get rid of this error.

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• How do I find the top N batters per year?

  - by Drew Stephens

  I'm playing around with the Lahman Baseball Database in a MySQL instance. I want to find the players who topped home runs (HR) for each year. The Batting table has the following (relevant parts) of its schema: +-----------+----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+----------------------+------+-----+---------+-------+ | playerID | varchar(9) | NO | PRI | | | | yearID | smallint(4) unsigned | NO | PRI | 0 | | | HR | smallint(3) unsigned | YES | | NULL | | +-----------+----------------------+------+-----+---------+-------+ For each year, every player has an entry (between hundreds and 12k per year, going back to 1871). Getting the top N hitters for a single year is easy: SELECT playerID,yearID,HR FROM Batting WHERE yearID=2009 ORDER BY HR DESC LIMIT 3; +-----------+--------+------+ | playerID | yearID | HR | +-----------+--------+------+ | pujolal01 | 2009 | 47 | | fieldpr01 | 2009 | 46 | | howarry01 | 2009 | 45 | +-----------+--------+------+ But I'm interested in finding the top 3 from every year. I've found solutions like this, describing how to select the top from a category and I've tried to apply it to my problem, only to end up with a query that never returns: SELECT b.yearID, b.playerID, b.HR FROM Batting AS b LEFT JOIN Batting b2 ON (b.yearID=b2.yearID AND b.HR <= b2.HR) GROUP BY b.yearID HAVING COUNT(*) <= 3; Where have I gone wrong?

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• Tabbed javascript widget for a Rails app

  - by neilc

  A user registers on our Rails app and they're given javascript to embed a widget in their website. The widget has a tabbed interface, like the JQuery tabs http://stilbuero.de/jquery/tabs_3/. iFrames have been tested, but the widget form factor and cross-domain policy negates the use of iframes. The widget is very dynamic and will often update the DOM with new content - and because of cross-domain policy, it looks as though JSONP is necessary. I understand that 'widget.js.erb' needs to create the widget layout, reference a stylesheet, render the tabs, etc - but once a tab is clicked, how does the widget request the content from the Rails app and render it in the DOM?

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• How to get dynamic SQL result from SP in entity framework?

  - by KentZhou

  Suppose I have following SP to run a dynamic sql ALTER PROCEDURE [dbo].[MySP] AS BEGIN declare @sql varchar(4000) select @sql = 'select cnt = count(*) from Mytable ..... '; exec (@sql) END then in edmx, I add the sp and import function for this sp. the return type is scalars int32. then I want to use this function in code like: int? result = context.MySP(); I got error said "cannot implicitly convert type System.Data.Objects.ObjectResults to int?" If use var result = context.MySP(); then Single() cann't be applied to context.MySP(). How to get the result for this case?

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• python iterators and thread-safety

  - by Igor

  I have a class which is being operated on by two functions. One function creates a list of widgets and writes it into the class: def updateWidgets(self): widgets = self.generateWidgetList() self.widgets = widgets the other function deals with the widgets in some way: def workOnWidgets(self): for widget in self.widgets: self.workOnWidget(widget) each of these functions runs in it's own thread. the question is, what happens if the updateWidgets() thread executes while the workOnWidgets() thread is running? I am assuming that the iterator created as part of the for...in loop will keep some kind of reference to the old self.widgets object? So I will finish iterating over the old list... but I'd love to know for sure.

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• c# wrapper for a c DLL

  - by Without me Its just Aweso

  I'm attempting to write a wrapper so that my C# application can use a DLL written in C. Here is a method defintion that i'm trying to wrap: void methodA(const uint32_t *data); //c header declaration The issue I'm having is trying to figure out how to give a equivalent pointer from c#. In c# I want it to operate on a: UInt32 data[] //my c# object i want to be able to pass in but how do I give an equivalent pointer in my wrapper? I have tried ref data //my attempt at giving an equivalent pointer to the DLL but that doesnt seem to be working. Using debug statements in the DLL I can see that the values it gets that way are not what I'm attempting to pass in. So my question boils down to have do I properly wrap a c fuction that is using a pointer to reference an array?

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• How can I access data that's stored in my App Delegate from my various view controllers?

  - by BeachRunnerJoe

  This question is similar to this other post, but I'm new to iPhone development and I'm getting used to the good practices for organizing my data throughout my app. I understand the ApplicationDelegate object to be the best place to manage data that is global to my app, correct? If so, how can I access data that's stored in my App Delegate from various view controllers? Specifically, I have an array of table section titles for my root table view controller created as such... appdelegate.m sectionTitles = [[NSArray alloc] initWithObjects: @"Title1", @"Title2", @"Title3", nil]; rootViewController.appDelegate = self; and I need to access it throughout the different views of my app, like such... rootviewcontroller.m NSUInteger numSections = [self.appDelegate.sectionTitles count]; Is this the best way to do it or are there any reasons I should organize my data a better way? Thanks so much in advance for your help!

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• Nested class with hidden constructor impossible in c#?

  - by luckyluke

  I' ve been doing some programming lately and faced an issue which i found weird in c#. (at least for me) public class Foo { //whatever public class FooSpecificCollection : List<Bar> { //implementation details } public FooSpecificCollection GetFoosStuff() { //return the collection } } I want the consumer of Foo to be able to obtain a reference to FooSpecificCollection, even perform some operations on it. Maybe even set it to some other property of Foo or smth like that, but not To be able to CREATE an instance of this class. (the only class that should be able to instatiate this collection should be Foo. Is my request really that far-fetched? I know that people way smarter defined c# but shouldn't there be such an option that a parent class can create a nested class instance but nobody else can't. So far I created a solution to make an abstract class, or interface available through the property and implement a concrete private class that is not available anywhere else. Is this a correct way to handle such a situation.?

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• How to index a string like "aaa.bbb.ddd-fff" in Lucene?

  - by user46703

  Hi, I have to index a lot documents that contain reference numbers like "aaa.bbb.ddd-fff". The structure can change but it's always some arbitrary numbers or characters combined with "/","-","_" or some other delimiter. The users want to be able to search for any of the substrings like "aaa" or "ddd" and also for combinations like "aaa.bbb" or "ddd-fff". The best I have been able to come up with is to create my own token filter modeled after the synonym filter in "Lucene in action" which spits out multiple terms for each input. In my case I return "aaa.bbb", "bbb.ddd","bbb.ddd-fff" and all other combinations of the substrings. This works pretty well but when I index large documents (100MB) that contain lots of such strings I tend to get out of memory exceptions because my filter returns multiple terms for each input string. Is there a better way to index these strings?

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• Is there anything wrong with my Factory class?

  - by Alex

  class PieceFactory { @SuppressWarnings("rawtypes") public Piece createPiece(String pieceType) throws Throwable{ Class pieceClass = Class.forName(pieceType); Piece piece = (Piece) pieceClass.newInstance(); return piece; } } I'm not all used to handling exceptions yet therefore I'm just throwing them, but everywhere I use a method that uses this factory it tells me I have to throw exceptions like throwable. For example, in one of my classes I have a method that instantiates a lot of objects using the method that uses the factory. I can use the method in that class by just throwing the exception, however it won't work if I try to pass a reference to that class to another class and then use the method from there. Then it forces me to try catch the exception. I probably don't need a factory but it seemed interesting and I'd like to try to use patterns. The reason I created the factory was that I have 6 subclasses of Piece and I wan't to use a method to instantiate them by passing the type of subclass I want as an argument to the method.

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• How can you tell the source of the data when using the Stream.BeginRead Method?

  - by xarzu

  When using the Stream.BeginRead Method, and you are reading from a stream into a memory, how is it determined where you are reading the data from? See: http://msdn.microsoft.com/en-us/library/system.io.stream.beginread.aspx In the list of parameters, I do not see one that tells where the data is being read from: Parameters buffer Type: System.Byte[] The buffer to read the data into. offset Type: System.Int32 The byte offset in buffer at which to begin writing data read from the stream. count Type: System.Int32 The maximum number of bytes to read. callback Type: System.AsyncCallback An optional asynchronous callback, to be called when the read is complete. state Type: System.Object A user-provided object that distinguishes this particular asynchronous read request from other requests.

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• Help for a Sql statement

  - by stighy

  Hy at all, today is the day of ...question. I've a single table, with a relation master-detail like this: RecordID MasterID Field1 Field2 .... NrDetail 1 0 xxx yyyy 1 2 0 aaaa bbbb 2 3 1 hhhhh ssss 0 4 2 eee sssss 0 5 2 jjj hhhh 0 As you can see, NrDetail contain the total of "child record". Unfortunately, i've to create this field... and i would like to write it in my table. So my SQL question is: how to do this type of SQL to write the field NrDetail ? Something like: UPDATE table SET NrDetail= (SELECT COUNT(*) as Total FROM table WHERE MasterID= RecordID) But i think there's some mistake... Thank you in advance !

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• How can I catch runtime error in C++

  - by Yan Cheng CHEOK

  By referring to http://stackoverflow.com/questions/315948/c-catching-all-exceptions try { int i = 0; int j = 0/i; /* Division by 0 */ int *k = 0; std::cout << *k << std::endl; /* De-reference invalid memory location. */ } catch (...) { std::cout << "Opps!" << std::endl; } The above run-time error are unable to be detected. Or, am I having wrong expectation on C++ exception handling feature?

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• JQuery-tmpl Template Switching Not working.

  - by Mike

  I'm trying to implement "more/less" functionality using the official jquery-tmpl plugin. I've looked at the examples, but I cannot seem to get the functionality to work in my own implementation. When I click on one of my "More" buttons, I seem to get an error thrown of: Uncaught TypeError: Property 'tmpl' of object #<an Object> is not a function This is my implementation here From what I can tell, the example I'm trying to replace is doing the following: Render the "Master" template On-click: Find the corresponding template object (tmplItem) to the clicked element. Pass in reference to a new template. Call the update function to re-render. Have I understood the documentation wrong? From what I can tell I'm doing the same thing as the example on the official documentation.

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• Form to sort an index in rails

  - by shmichael

  I'm a newcomer to Rails. I want to build a simple form that determines the sort order of a list. I've implemented a form in the likes of - <%= radio_button_tag :sort, "rating" %> <%= label_tag :sort_rating, "order by rating" %> <%= radio_button_tag :sort, "name" %> <%= label_tag :sort_name, "order by name" %> And now I am unsure how to implement the sort at the controller/model level. The aspects I am puzzled about are: Where should the sort be performed How could the sort parameter be persisted How could the code be reused Right now, I can't even get the selected sort method to remain selected after a submit. I would most appreciate any guidance or reference to an example.

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• Express any number as the sum of 4 prime numbers [Doubts]

  - by WarDoGG

  I was give a problem to express any number as sum of 4 prime numbers. Conditions: Not allowed to use any kind of database. Maximum execution time : 3 seconds Numbers only till 100,000 If the splitting is NOT possible, then return -1 What i did : using the sieve of eratosthenes, i calculated all prime numbers till the specified number. looked up a concept called goldbach conjecture which expresses an even number as the summation of 2 primes. However, i am stuck beyond that. Can anyone help me on this one as to what approach u might take ? The sieve of eratosthenes is taking 2 seconds to count primes till 100,000 :(((

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• MySQL indexes: how do they work?

  - by bob-the-destroyer

  I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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• trim last "," delimiter of a string in vb.net

  - by gerfe

  this is my code - With ad.Tables(2) For i As Integer = 0 To .Rows.Count - 1 If .Rows(i)("name") & "" <> "" Then temp &= .Rows(i)("name") & ", " End If Next End With temp = temp.Trim(",") testing &= "&Name=" & temp & vbCrLf with this is get a comma in the end of the string. but if i do this temp = temp.Trim.Trim(",") all commas are deleted. How do i keep all commas and only delete the last one?

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• Entity framework (3.5): How to translate a certain LINQ query to eSQL?

  - by Sebastian P.R. Gingter

  Hi there, I have the following LINQ query that I need to translate to Entity SQL /eSQL): return (ObjectQuery<User>) from user in Users where !user.Roles.Any(r => r.AnIntegerProperty < 0) select user; User.Roles is an navigation property to the n:m relation to Roles and there also is a Role.Users navigation property the other way round. There aren't User_Roles or Roles_User Entities available in the model, and I can't add these. I also can't use the LINQ statement here, because I need to add .OrderBy("it." + propertyname) (comes from another source, can't change that too) later on which is not possible if the ObjectQuery is build with linq. So how do I translate this to eSQL? And where can I find good eSQL samples? I searched for a whole day until now and must admit that eSQL reference is lousy and there aren't any usable examples around the web.

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• Uri for bitmap in subfolder (c# wpf)

  - by the empirical programmer

  I have a wpf app where I'm using an image. To reference the image I use: Uri uri = new Uri("pack://application:,,,/assemblyName;Component/myIcon.png"); BitmapImage(uri) If I add the png directly under the csproj file (with its properties BuildAction=Resource) then it works fine. But I want to move it to a subfolder under the csproj. Another SO question asked about bitmaps\uri's (857732) and an answer linked to this msdn. So I tried : Uri uri = new Uri("pack://application:,,,/assemblyName;Component/Icons/myIcon.png"); But that did not work. Any ideas?

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• Accessing ArrayBuffer from PHP $_POST after xmlHTTPrequest send()

  - by Dan

  I'm following the tuitions on XMLHttpRequest 2 from : https://developer.mozilla.org/en/DOM/XMLHttpRequest/Sending_and_Receiving_Binary_Data and http://www.html5rocks.com/en/tutorials/file/xhr2/#toc-send-arraybuffer They're great tutorials for the client side, and here is a working extract from my script: var imagebuffer = new ArrayBuffer(size); // create the readonly memory buffer var imagedata= new Uint8Array(imagebuffer); // create a view to manipulate data // do some cool stuff with imagedata var exchange=new XMLHttpRequest(); exchange.open("POST",url,true); exchange.send(arraybuffer); So far so good, and I can see from the both client and server control panels that plenty of data is being transferred. Here's my problem: how do I access the ArrayBuffer with PHP at the server? I'm used to the $_POST superglobal wanting parameters passing from a HTML form so it can be accessed as an array but I can't find any reference for how to access this binary array and stick it in my MySQL database.

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• get the row number from table view

  - by Faizan Tanveer

  i am new in iphone development, i am using table view to list name of the student, what i want to do is i want to get the row number of the cell the user pressed , currently i can get the name(string) of the cell, //code in didSelectRowAtIndexPath //the obj.name where is a string, it works fine obj.name=[obj.studentname objectAtIndex:indexPath.row]; //if i try obj.num , where num is nsinteger .i am getting errors of type i dnt understand obj.num=[[obj.studentname objectAtIndex:indexPath.row]count]; i even tried but i cant get the number. example if faizan lies on 12th cell. what i want to do is,is save 12 in a number and show it on the next view label.i cant put it in the variable thanks for your help in advance

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