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  • Find location using only distance and bearing?

    - by pinnacler
    Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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  • derby + hibernate ConstraintViolationException using manytomany relationships

    - by user364470
    Hi, I'm new to Hibernate+Derby... I've seen this issue mentioned throughout the google, but have not seen a proper resolution. This following code works fine with mysql, but when I try this on derby i get exceptions: ( each Tag has two sets of files and vise-versa - manytomany) Tags.java @Entity @Table(name="TAGS") public class Tags implements Serializable { @Id @GeneratedValue(strategy=GenerationType.AUTO) public long getId() { return id; } @ManyToMany(targetEntity=Files.class ) @ForeignKey(name="USER_TAGS_FILES",inverseName="USER_FILES_TAGS") @JoinTable(name="USERTAGS_FILES", joinColumns=@JoinColumn(name="TAGS_ID"), inverseJoinColumns=@JoinColumn(name="FILES_ID")) public Set<data.Files> getUserFiles() { return userFiles; } @ManyToMany(mappedBy="autoTags", targetEntity=data.Files.class) public Set<data.Files> getAutoFiles() { return autoFiles; } Files.java @Entity @Table(name="FILES") public class Files implements Serializable { @Id @GeneratedValue(strategy=GenerationType.AUTO) public long getId() { return id; } @ManyToMany(mappedBy="userFiles", targetEntity=data.Tags.class) public Set getUserTags() { return userTags; } @ManyToMany(targetEntity=Tags.class ) @ForeignKey(name="AUTO_FILES_TAGS",inverseName="AUTO_TAGS_FILES") @JoinTable(name="AUTOTAGS_FILES", joinColumns=@JoinColumn(name="FILES_ID"), inverseJoinColumns=@JoinColumn(name="TAGS_ID")) public Set getAutoTags() { return autoTags; } I add some data to the DB, but when running over Derby these exception turn up (the don't using mysql) Exceptions SEVERE: DELETE on table 'FILES' caused a violation of foreign key constraint 'USER_FILES_TAGS' for key (3). The statement has been rolled back. Jun 10, 2010 9:49:52 AM org.hibernate.event.def.AbstractFlushingEventListener performExecutions SEVERE: Could not synchronize database state with session org.hibernate.exception.ConstraintViolationException: could not delete: [data.Files#3] at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2712) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2895) at org.hibernate.action.EntityDeleteAction.execute(EntityDeleteAction.java:97) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:260) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184) at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:613) at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) at $Proxy13.flush(Unknown Source) at data.HibernateORM.removeFile(HibernateORM.java:285) at data.DataImp.removeFile(DataImp.java:195) at booting.DemoBootForTestUntilTestClassesExist.main(DemoBootForTestUntilTestClassesExist.java:62) I have never used derby before so maybe there is something crutal that i'm missing 1) what am I doing wrong? 2) is there any way of cascading properly when I have 2 many-to-many relationships between two classes? Thanks!

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  • Sorting XML generated by Castor

    - by Java Guy
    Hello, I am using Castor for XML Binding.. We need to sort the XML based on two different fields. Is there way we can specify the sort order in castor while marshalling? Which will be a better approach to do this sorting, if castor don't have this feature.

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  • Mysql: Perform of NOT EXISTS. Is it possible to improve permofance?

    - by petRUShka
    I have two tables posts and comments. Table comments have post_id attribute. I need to get all posts with type "open", for which there are no comments with type "good" and created date MAY 1. Is it optimal to use such SQL-query: SELECT posts.* FROM posts WHERE NOT EXISTS ( SELECT comments.id FROM comments WHERE comments.post_id = posts.id AND comments.comment_type = 'good' AND comments.created_at BETWEEN '2010-05-01 00:00:00' AND '2010-05-01 23:59:59') I'm not sure that NOT EXISTS is perfect construction in this situation.

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  • groovyx.net.ws.WSClient is having problems with ''soapenc:Array' Any workaround?

    - by ?????
    I'm trying to call a webservice (implemented with a .NET/ASP system) from groovy/grails using WSClient. I have no trouble accessing this service using the SOAPClient debugger (Todd Ditchendorf's program for OSX), but when i try it via groovy/grails, I get the error undefined simple or complex type 'soapenc:Array' Is there any solution? Looking at it with wireshark: It seems to have thrown this error even before it gets a chance to perform the transaction. The error is thrown right after WSClient has downloaded the second of two schemas referenced in he WSDL.

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  • jQuery $.each(arr, foo) versus $(arr).each(foo)

    - by Brian M. Hunt
    In jQuery, what's the difference between the following two constructions of jQuery.each: // Given var arr = [1,2,3,4], results = [], foo = function (index, element) { /* something done to/with each element */ results.push(element * element); // arbitrary thing. } // construction #1 $.each(arr, foo); // results = [1,4,9,16] // construction #2 $(arr).each(foo); // results = [1,4,9,16] Is there any difference, or is it purely syntax?

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  • How to change bahaviour enter/backspace pressed in WYMEDITOR

    - by liysd
    Hi all, In Google Chrome after pressing enter key in WYMEDITOR a new is created. How to change it? I would rather insert tag as it happens after shift-enter combination. (In fact shif-enter creates two ). Similar question concerns backspace pressed on the beginning of paragraph. How to change this behaviour to erase paragraph (or other) only when it is empty and do nothing otherwise. I'll be greatful for any hints.

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  • How to mix mongodb and a traditional db in Rails?

    - by Jonathan
    I am considering using MongoDB (mongo-mapper) for a portion of my rails application. I am not ready to go whole hog MongoDB because there are too many useful gems that depend on a traditional DB. That being said there are parts of my application that would be great to leverage a document database. Has anyone had success mixing the two approaches? How do you link activerecord models with mongomapper models? Thanks, Jonathan

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  • PostgreSQL data comparsion tool

    - by user179056
    Hello, I am looking for a tool/command which can compare data between two PostgreSQL databases. The reason to do this is to have some external verification that the SQL script responsible for data migration from one PostgreSQL database to the other have been written correctly. Any pointers would be appreciated regards Sameer

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  • Groovy markupbuilder tags

    - by john renfrew
    Is there a way to modify the code from a previous answer import groovy.xml.MarkupBuilder def writer = new StringWriter() def builder = new MarkupBuilder(writer) def awaiting = ['one', 'two', 'three'] builder.html { ul { awaiting.each { li(it.toString()) } } } println writer.toString() so that if you add a tag instead that you send it - like builder.html{ tag{ awaiting.each{} } } return result could be 'ol' or 'ul' for example

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  • Website url whitelists

    - by buggedcom
    I'm building a user content parser and am adding an automatic link parser. I'm adding a dialogue, that confirms that the user wants to go to the particular site being linked to. This is for two reasons. Anti phishing and spam combating. However I want to be able to disable both the dialogue and nofollow additions with commonly used websites, so I'm building a whitelist. Are there any common whitelists about or should I start building one from scratch?

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  • t-sql grouping query

    - by stackoverflowuser
    Hi based on the following table Name --------- A A A B B C C C I want to add another column to this table called 'OnGoing' and the values should alternate for each group of names. There are only two values 'X' and 'Y'. So the table will look like Name OnGoing ---------------- A X A X A X B Y B Y C X C X C X how to write such a query that can alternate the values for each group of names.

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  • Problem with final branch in a parallel activity

    - by Dan Revell
    This might seem like a silly thing to say, the final branch in a parallel activity so I'll clarify. It's a parallel activity with three branches each containing a simple create task, on task changed and complete task. The branch containing the task that is last to complete seems to break. So every task works in it's own right, but the last one encounters a problem. Say the user clicks the final tasks link to open the attached infopath form and submits that. Execution gets to the event handler for that onTaskChanged where a taskCompleted variable gets set to true which will exit the while loop. I've successfully hit a breakpoint on this line so I know that happens. However the final activity in that branch, the completeTask doesn't get hit. When submit is clicked in the final form, the operation in progess screen says of for quite a while before returning to the workflow status page. The task that was opened and submitted says "Not Started". I can disable any of the branches to leave only two, but the same problem happens with the last to be completed. Earlier on in the workflow I do essencially the same thing. I have another 3 branch parallel activity with each brach containing a task. This one works correctly which leads me to believe that it might be a problem with having two parallel activites in the same sequential workflow. I've considered the possibility that it might be a correlation token problem. The token that every task branch uses is unique to that branch and it's owner activity name is est to that of the branch. It stands to reason that if the task complete variable is indeed getting set to true but the while loop isn't being exited, then there's a wire crossing with the variable somewhere. However I'd still have thought that the task status back on the workflow status page would at least say that the task is in progress. This is a frustrating show stopper of a bug for me. Any thoughts or suggestions would be much appricated so I can investigate them.

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  • Brute force a website

    - by bigbrute
    Hi, there's a website i visit that always has these code giveaways where you get a prize for cracking the code. The code is in a format like this: QBYQC-Y??T3-W7G4R-QP4HG-2WQPT and they'll give you a hint such as two letters or a number and a letter. The solution to this is easy, brute-forcing it. However, I need the software that will make my browser repeatedly enter a new combination. What software can I use on Mac (and if not, Windows)?

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  • Managing the interval for horizontal axis in flex

    - by Roshan
    Hi Guys, How can we manage the horizontalaxis interval in flex chart? What actually happening is , the data is inserted between two interval levels and its causing readability problem when we draw line grids in graph. The data point is shown in between the data grids. How can we move the axis or manage the data points?

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  • UIScrollView with 3 UITableViews

    - by drDevPep
    I made a UIScrollView like the Weather.app. On the first page I've placed a UITableView which shows data loaded from a website. On the second and on the first page I also want to place a UITableView. The other two tables should also load data from a website, but from another URL. Now my question. How can I set up a UIScrollView with 3 UITableViews in it?

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  • Frequency Table by user in SQL

    - by Roberto
    Very basic SQL question (DB is MySQL): I want a table of number of transactions by users. User ID Transaction count 1 43 2 213 3 0 4 23 5 0 In a table I have the two relevant records (user_id and buy_count). How could I get the table I want? Thanks, Roberto

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  • quick question about learning c#

    - by Oliver Bayes-Shelton
    Hi, I am looking to buy my first c# book, at the moment amazon have a special offer on two titles Sams Teach Yourself the C# Language and Sams Teach Yourself Visual C# 2008 my qutestion is if their a difference between visual C# and C# ? also which book would be better for an intro to C#

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  • File upload in asp.net mvc using ajax

    - by Maxim
    Hello! i have a simple html form with two controls: input-text and input-file i need to write an ajax query (using jquery is better) to send data (file and value from text field to mvc acton) i wrote $.ajax({ type: "POST", url: "/controller/acton", enctype: 'multipart/form-data', data: 'text=' + $("#text").val() + '&file=' + $("#file").val() ... and in controller: [HttpPost] public ActionResult StoreItem(FormCollection forms) { foreach (string inputTagName in Request.Files) ... returns null in Request... Thank you

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  • What is your favourite cleverly written functional code?

    - by sdcvvc
    What are your favourite short, mind-blowing snippets in functional languages? My two favourite ones are (Haskell): powerset = filterM (const [True, False]) foldl f v xs = foldr (\x g a -> g (f a x)) id xs v -- from Hutton's tutorial (I tagged the question as Haskell, but examples in all languages - including non-FP ones - are welcome as long as they are in functional spirit.)

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  • ruby-on-rails: route not found in partial

    - by cbrulak
    I have a controller: twitter_status with two functions: tweet_post tweet_comment in routes.rb I have map.resources :twitter_status In my show post view, I have a partial: _show and _show_comment In _show I have: tweet_post_twitter_status_path (...) and that works fine. But in the in _show_comment partial I have: tweet_comment_twitter_status_path (...) but I have a NoMethodError in the show.html.erb view. Any ideas?

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