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  • Bind a generic list to a listbox and also use a datatemplate

    - by muku
    Hello, I'm trying to implement something quite simple but I'm on my first steps in WPF and I'm having some problems. I have a class called Component which has a property called Vertices. Vertices is a generic List of type Point. What I want is to bind the vertices property to a listbox. This is easy by using this code in my XAML in the listbox declaration: ItemsSource="{Binding Path=Component.Vertices, Mode=OneWay, Converter={StaticResource verticesconverter},UpdateSourceTrigger=PropertyChanged}" The tricky part is when I try to create a datatemplate for the listbox. I want each row of the listbox to display a textbox with the values of the Vertex (Point.X, Point.Y) and a button to allow me to delete the item. Could you help me on the datatemplate definition. The code below doesn't work to bind the X,Y values into two separate textboxes. Could you point me on the mistake and why nothing is displayed in the textboxes? <ListBox ItemsSource="{Binding Path=Component.Vertices, Mode=OneWay,UpdateSourceTrigger=PropertyChanged}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal" Margin="0,10,0,0"> <TextBox Text="{Binding X}" MinWidth="35" MaxWidth="35"/> <TextBox Text="{Binding Y}" MinWidth="35" MaxWidth="35"/> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> /ListBox>

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  • Float addition promoted to double?

    - by Andreas Brinck
    I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = 0.1f; float z = x + y; assert(z == x + y); //This assert is triggered! (Atleast with visual studio 2008) The reason seems to be that the expression x + y is promoted to double and compared with the truncated version in z. (If i change z to double the assert isn't triggered). I can see that for precision reasons it would make sense to perform all floating point arithmetics in double precision before converting the result to single precision. I found the following paragraph in the standard (which I guess I sort of already knew, but not in this context): 4.6.1. "An rvalue of type float can be converted to an rvalue of type double. The value is unchanged" My question is, is x + y guaranteed to be promoted to double or is at the compiler's discretion? UPDATE: Since many people has claimed that one shouldn't use == for floating point, I just wanted to state that in the specific case I'm working with, an exact comparison is justified. Floating point comparision is tricky, here's an interesting link on the subject which I think hasn't been mentioned.

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  • How to access hidden template in unnamed namespace?

    - by Johannes Schaub - litb
    Here is a tricky situation, and i wonder what ways there are to solve it namespace { template <class T> struct Template { /* ... */ }; } typedef Template<int> Template; Sadly, the Template typedef interferes with the Template template in the unnamed namespace. When you try to do Template<float> in the global scope, the compiler raises an ambiguity error between the template name and the typedef name. You don't have control over either the template name or the typedef-name. Now I want to know whether it is possible to: Create an object of the typedefed type Template (i.e Template<int>) in the global namespace. Create an object of the type Template<float> in the global namespace. You are not allowed to add anything to the unnamed namespace. Everything should be done in the global namespace. This is out of curiosity because i was wondering what tricks there are for solving such an ambiguity. It's not a practical problem i hit during daily programming.

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  • Computing "average" of two colors

    - by Francisco P.
    This is only marginally programming related - has much more to do w/ colors and their representation. I am working on a very low level app. I have an array of bytes in memory. Those are characters. They were rendered with anti-aliasing: they have values from 0 to 255, 0 being fully transparent and 255 totally opaque (alpha, if you wish). I am having trouble conceiving an algorithm for the rendering of this font. I'm doing the following for each pixel: // intensity is the weight I talked about: 0 to 255 intensity = glyphs[text[i]][x + GLYPH_WIDTH*y]; if (intensity == 255) continue; // Don't draw it, fully transparent else if (intensity == 0) setPixel(x + xi, y + yi, color, base); // Fully opaque, can draw original color else { // Here's the tricky part // Get the pixel in the destination for averaging purposes pixel = getPixel(x + xi, y + yi, base); // transfer is an int for calculations transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.red + (float) pixel.red)/2); // This is my attempt at averaging newPixel.red = (Byte) transfer; transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.green + (float) pixel.green)/2); newPixel.green = (Byte) transfer; // transfer = (int) ((float) ((float) 255.0 - (float) intensity)/255.0 * (((float) color.blue) + (float) pixel.blue)/2); transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.blue + (float) pixel.blue)/2); newPixel.blue = (Byte) transfer; // Set the newpixel in the desired mem. position setPixel(x+xi, y+yi, newPixel, base); } The results, as you can see, are less than desirable. That is a very zoomed in image, at 1:1 scale it looks like the text has a green "aura". Any idea for how to properly compute this would be greatly appreciated. Thanks for your time!

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  • Passing filtering functions to Where() in LINQ-to-SQL

    - by Daniel
    I'm trying to write a set of filtering functions that can be chained together to progressively filter a data set. What's tricky about this is that I want to be able to define the filters in a different context from that in which they'll be used. I've gotten as far as being able to pass a very basic function to the Where() clause in a LINQ statement: filters file: Func<item, bool> returnTrue = (i) => true; repository file: public IQueryable<item> getItems() { return DataContext.Items.Where(returnTrue); } This works. However, as soon as I try to use more complicated logic, the trouble begins: filters file: Func<item, bool> isAssignedToUser = (i) => i.assignedUserId == userId; repository file: public IQueryable<item> getItemsAssignedToUser(int userId) { return DataContext.Items.Where(isAssignedToUser); } This won't even build because userId isn't in the same scope as isAssignedToUser(). I've also tried declaring a function that takes the userId as a parameter: Func<item, int, bool> isAssignedToUser = (i, userId) => i.assignedUserId == userId; The problem with this is that it doesn't fit the function signature that Where() is expecting: Func<item, bool> There must be a way to do this, but I'm at a loss for how. I don't feel like I'm explaining this very well, but hopefully you get the gist. Thanks, Daniel

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  • Atomic swap in GNU C++

    - by Steve
    I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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  • how to store/model users/faceboook users/linkedin users, etc, with ActiveRecord?

    - by crankharder
    My app has "normal" users: those which come through a typical signup page facebook(FB) users: those which come from Facebook connect "FB-normal" users: a user that can log with both email/password * FB connect Further, there's the a slew of other openID-ish login methods (I don't think openID itself will be acceptable since it doesn't link up the accounts and allow the 3rd party specific features (posting to twitter, adding a FB post, etc etc)) So, how do I model this? Right now we have User class with #facebook_user? defined -- but it gets messy with the "FB-normal" users - plus all the validations become very tricky and hard to interpret. Also, there are methods like #deliver_password_reset! which make no sense in the context for facebook-only users. (this is lame) I've thought out STI (User::Facebook, User::Normal, User::FBNormal, etc.) This makes validations super slick, but it doesn't scale to other connection types, and all the permutations between them... User::FacebookLinkedInNormal(wtf?) Doing this with a bunch of modules I think would suck a lot. Any other ideas?

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  • retrieve value from hashtable with clone of key; C#

    - by Johnny
    I would like to know if there is any possible way to retrieve an item from a hashtable using a key that is identical to the actual key, but a different object. I understand why it is probably not possible, but I would like to see if there is any tricky way to do it. My problem arises from the fact that, being as stupid as I am, I created hashtables with int[] as the keys, with the integer arrays containing indices representing spatial position. I somehow knew that I needed to create a new int[] every time I wanted to add a new entry, but neglected to think that when I generated spatial coordinate arrays later they would be worthless in retrieving the values from my hashtables. Now I am trying to decide whether to rearrange things so that I can store my values in ArrayLists, or whether to search through the list of keys in the Hashtable for the one I need every time I want to get a value, neither of the options being very cool. Unless of course there is a way to get //1 to work like //2! Thanks in advance. static void Main(string[] args) { Hashtable dog = new Hashtable(); //1 int[] man = new int[] { 5 }; dog.Add(man, "hello"); int[] cat = new int[] { 5 }; Console.WriteLine(dog.ContainsKey(cat)); //false //2 int boy = 5; dog.Add(boy, "wtf"); int kitten = 5; Console.WriteLine(dog.ContainsKey(kitten)); //true; }

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  • CEIL is one too high for exact integer divisions

    - by Synetech
    This morning I lost a bunch of files, but because the volume they were one was both internally and externally defragmented, all of the information necessary for a 100% recovery is available; I just need to fill in the FAT where required. I wrote a program to do this and tested it on a copy of the FAT that I dumped to a file and it works perfectly except that for a few of the files (17 out of 526), the FAT chain is one single cluster too long, and thus cross-linked with the next file. Fortunately I know exactly what the problem is. I used ceil in my EOF calculation because even a single byte over will require a whole extra cluster: //Cluster is the starting cluster of the file //Size is the size (in bytes) of the file //BPC is the number of bytes per cluster //NumClust is the number of clusters in the file //EOF is the last cluster of the file’s FAT chain DWORD NumClust = ceil( (float)(Size / BPC) ) DWORD EOF = Cluster + NumClust; This algorithm works fine for everything except files whose size happens to be exactly a multiple of the cluster size, in which case they end up being one cluster too much. I thought about it for a while but am at a loss as to a way to do this. It seems like it should be simple but somehow it is surprisingly tricky. What formula would work for files of any size?

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  • Check if file is locked or catch error for trying to open

    - by Duncan Matheson
    I'm trying to handle the problem where a user can try to open, with an OpenFileDialog, a file that is open by Excel. Using the simple FileInfo.OpenRead(), it chucks an IOException, "The process cannot access the file 'cakes.xls' because it is being used by another process." This would be fine to display to the user except that the user will actually get "Debugging resource strings are unavailable" nonsense. It seems not possible to open a file that is open by another process, since using FileInfo.Open(FileMode.Open, FileAccess.Read, FileShare.ReadWrite) chucks a SecurityException, "File operation not permitted. Access to path 'C:\whatever\cakes.xls' is denied.", for any file. Rather unhelpful. So it's down to either finding some way of checking if the file is locked, or trying to catch the IOException. I don't want to catch all IOExceptions and assume they're all locked file errors, so I need some sort of way of classifying this type of exception as this error... but the "Debugging resource strings" nonsense along with the fact that that message itself is probably localized makes it tricky. I'm partial trust, so I can't use Marshal.GetHRForException. So: Is there any sensible way of either check if a file is locked, or at least determining if this problem occurred without just catching all IOExceptions?

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  • Raising events and object persistence in Django

    - by Mridang Agarwalla
    Hi, I have a tricky Django problem which didn't occur to me when I was developing it. My Django application allows a user to sign up and store his login credentials for a sites. The Django application basically allows the user to search this other site (by scraping content off it) and returns the result to the user. For each query, it does a couple of queries of the other site. This seemed to work fine but sometimes, the other site slaps me with a CAPTCHA. I've written the code to get the CAPTCHA image and I need to return this to the user so he can type it in but I don't know how. My search request (the query, the username and the password) in my Django application gets passed to a view which in turn calls the backend that does the scraping/search. When a CAPTCHA is detected, I'd like to raise a client side event or something on those lines and display the CAPTCHA to the user and wait for the user's input so that I can resume my search. I would somehow need to persist my backend object between calls. I've tried pickling it but it doesn't work because I get the Can't pickle 'lock' object error. I don't know to implement this though. Any help/ideas? Thanks a ton.

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  • creating matrix with probabilities

    - by John Chan
    Hi all, I want to generate a matrix of NxN to test some code that I have where each row contains floats as the elements and has to add up to 1 (i.e. a row with a set of probabilities). Where it gets tricky is that I want to make sure that randomly some of the elements should be 0 (in fact most of the elements should be 0 except for some random ones to be the probabilities). I need the probabilities to be 1/m where m is the number of elements that are not 0 within a single row. I tried to think of ways to output this, but essentially I would need this stored in a C++ array. So even if I output to a file I would still have the issue of not having it in array as I need it. At the end of it all I need that array because I want to generate a Market Matrix file. I found an implementation in C++ to take an array and convert it to the market matrix file, so this is what I am basing my findings on. My input for the rest of the code takes in this market matrix file so I need that to be the primary form of output. The language does not matter, I just want to generate the file at the end (I found a way mmwrite and mmread in python as well) Please help, I am stuck and not really sure how to implement this.

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  • Printing to different printers using mozilla.

    - by Nick-ACNB
    I am currently creating a web application that will be deployed in an intranet environment. I chose firefox to be the browser that will run it. However, in the application I am building, I need to be able to print to different printers quickly since they use different paper size depending on what client is coming. To avoid many time-wasting mistakes that could occur, for instance someone choosing the wrong printer and wasting paper. Also, the time used to find the right printer for the job and then pressing print is considered too long in the current context. Is there any solution to this problem? I understand the potential security flaw behind this, but please be aware that this is solely an intranet project and that I can reduce the browser's security to the lowest since they don't access internet. I know there could be something doable behind IE (ActiveX or VBScript) but I am using firefox. Also, I guess there could also be something rather tricky that when you press print on the browser, it saves what needs to be printed to a DB and then there is an exe app that runs and fetch that DB every set ammount of time and print to the right printer. Any suggestion would be greatly appreciated. I doubt I am the only one to ever face this issue! :) Thank you very much.

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  • How to view shell commands used by eclipse "run configurations"

    - by gmale
    Given a "run configuration" in Eclipse, I want to print out the associated shell command that would be used to run it. For example: Right now, in Eclipse, if I click "play" it will run: mvn assembly:directory -Dmaven.test.skip=true I don't see that command, I just know that's what the IDE must run, at some point. However, some of the other run configurations are far more complex with long classpaths and virtual machine options and, frankly, sometimes I have no idea what the equivalent shell command would be (particularly when it comes to Flex). There must be some way to access the shell command that would be associated with a "Run Configuration" in Eclipse/Flex Builder. This information must be available, which leads me to believe someone has written a plugin to display it. Or maybe there's already an option built into Eclipse for accessing this. So is there a way to, essentially, convert an Eclipse run configuration into a shell command? (for context only: I'm asking because I'm writing a bash script that automates everything I do, during development--from populating the Database all the way to opening Firefox and clearing the cache before running the web app. So every command I run from the IDE needs to exist in the script. Some are tricky to figure out.)

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  • Entity Framework 4 Self Many-To-Many with Properties

    - by csharpnoob
    UPDATE: Solved by myself. Tricky but works. If you know a better solution, feel free to correct me. DESIGNER: CODE: Product product1 = new Product{key = "Product 1"}; sd.AddToProducts(product1); Product product2 = new Product{key = "Product 2"}; sd.AddToProducts(product2); Product product3 = new Product{key = "Product 3"}; ProductRelated pr = new ProductRelated(); pr.Products.Add(product1); pr.Products.Add(product2); product3.ProductRelateds.Add(pr); sd.AddToProducts(product3); CODE VIEW: foreach(var x in (from b in sd.Products select b)) { %><%=x.key %><br /> <% foreach (var y in x.ProductRelateds) { foreach (var k in y.Products) { %>- <%=k.key%><br /><%} } } OUTPUT Product1 Product2 Product3 - Product2 - Product1 QUESTION: Hi, i want to have a Self Reference for Releated Products on a Product Entity, something like here: http://my.safaribooksonline.com/9781430227038/modeling_a_many-to-many_comma_self-refer But i also want on the Many-To-Many Reference addional Properties like deleted, created etc. I tried to do it by another Entity "Related", but somehow it won't work. Does anyone had this Problem before? Is there any other Example? Thanks

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  • How is a referencing environment generally implemented for closures?

    - by Alexandr Kurilin
    Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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  • How to enter text into the "Write something..." box on Facebook and click Submit

    - by Peter Payne
    Hello, I am trying to manipulate Facebook pages in various ways, using Javascript browser elements. I'd need to be able to insert some text into the top "Type something..." box that shows on my site's fan page (or alternately, "click into" the field and I can type the text using GUI scripting), then click the "submit" button as if i'd done it by hand. It's tricky since the page is very Ajax heavy and I can't find the names of the elements I need to manipulate, let alone how to manipulate them as they're not using traditional form fields I'm used to. Can anyone help me figure out how to do this with javascript commands, which I'd be calling from Applescript on the Mac? Many thanks in advance. UPDATE Thanks for the comments below. Believe me, I am not trying to do anything spammy or douchy, mainly posting links to products that have gone live on page facebook page, but do it during the business day when people are on rather than at strange hours of the day. I am located in Japan so my sleep period is right when people are using FB. The solution I came up with for clicking the button was got using UI Browser, an outstanding tool if you're trying to script on the Mac. The script that clicked the button for me was: tell application "Safari" activate set thename to name of (get current tab of window 1) delay 3 tell application "System Events" tell process "Safari" try click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 3 of window thename -- this one works on the mini? on error click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 2 of window thename -- did not work end try end tell end tell end tell Hope this is useful to anyone.

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  • How to output multicolumn html without "widows"?

    - by user314850
    I need to output to HTML a list of categorized links in exactly three columns of text. They must be displayed similar to columns in a newspaper or magazine. So, for example, if there are 20 lines total the first and second columns would contain 7 lines and the last column would contain 6. The list must be dynamic; it will be regularly changed. The tricky part is that the links are categorized with a title and this title cannot be a "widow". If you have a page layout background you'll know that this means the titles cannot be displayed at the bottom of the column -- they must have at least one link underneath them, otherwise they should bump to the next column (I know, technically it should be two lines if I were actually doing page layout, but in this case one is acceptable). I'm having a difficult time figuring out how to get this done. Here's an example of what I mean: Shopping Link 3 Link1 Link 1 Link 4 Link2 Link 2 Link 3 Link 3 Cars Link 1 Music Games Link 2 Link 1 Link 1 Link 2 News As you can see, the "News" title is at the bottom of the middle column, and so is a "widow". This is unacceptable. I could bump it to the next column, but that would create an unnecessarily large amount of white space at the bottom of the second column. What needs to happen instead is that the entire list needs to be re-balanced. I'm wondering if anyone has any tips for how to accomplish this, or perhaps source code or a plug in. Python is preferable, but any language is fine. I'm just trying to get the general concept down.

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  • WCF: Exposed Object Model - stuck in a loop

    - by Mark
    Hi I'm working on a pretty big WSSF project. I have a normal object model in the business layer. Eg a customer has an orders collection property, when this is accessed then it loads from the data layer (lazy loading). An order has a productCollection property etc etc.. Now the bit I'm finding tricky is exposing this via WCF. I want to export a collection of orders. The client app will also need information about the customers. Using the WSSF data contract designer I have set it up so that customers have a property called "order collection". This is fine if you have a customer object and would like to look at the orders but if you have an order object there is no customer property so it doesn't work going up the hierarchy. I've tried adding a customer property to the orders object but then the code gets stuck in a loop when it loads the data contracts up. This is because it doesn't load on demand like in the business layer. I need to load all properties up before the objects can be sent out via WCF. It ends up loading an order, then the customer for that order, then the orders for that customer, then the customer for that order etc etc... I'm sure I've got all this wrong. Help!!

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  • C++ Program Flow: Sockets in an Object and the Main Function

    - by jfm429
    I have a rather tricky problem regarding C++ program flow using sockets. Basically what I have is this: a simple command-line socket server program that listens on a socket and accepts one connection at a time. When that connection is lost it opens up for further connections. That socket communication system is contained in a class. The class is fully capable of receiving the connections and mirroring the data received to the client. However, the class uses UNIX sockets, which are not object-oriented. My problem is that in my main() function, I have one line - the one that creates an instance of that object. The object then initializes and waits. But as soon as a connection is gained, the object's initialization function returns, and when that happens, the program quits. How do I somehow wait until this object is deleted before the program quits? Summary: main() creates instance of object Object listens Connection received Object's initialization function returns main() exits (!) What I want is for main() to somehow delay until that object is finished with what it's doing (aka it will delete itself) before it quits. Any thoughts?

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  • Escape whitespace in paths using nautilus script

    - by Tommy Brunn
    I didn't think this would be as tricky as it turned out to be, but here I am. I'm trying to write a Nautilus script in Python to upload one or more images to Imgur just by selecting and right clicking them. It works well enough with both single images and multiple images - as long as they don't contain any whitespace. In fact, you can upload a single image containing whitespace, just not multiple ones. The problem is that NAUTILUS_SCRIPT_SELECTED_FILE_PATHS returns all the selected files and directories as a space separated string. So for example, it could look like this: print os.environment['NAUTILUS_SCRIPT_SELECTED_FILE_PATHS'] /home/nevon/Desktop/test image.png /home/nevon/Desktop/test.jpg What I need is a way to -either in bash or Python- escape the spaces in the path - but not the spaces that delimit different items. Either that, or a way to put quotation marks around each item. The ultimate solution would be if I could do that in bash and then send the items as separate arguments to my python script. Something like: python uploader.py /home/nevon/Desktop/test\ image.png /home/nevon/Desktop/test.jpg I've tried RTFM'ing, but there doesn't seem to be a lot of good solutions for this. At least not that I've found. Any ideas?

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  • Generate random number from an arbitrary weighted list

    - by Fernando
    Here's what I need to do, I'll be doing this both in PHP and JavaScript. I have a list of numbers that will range from 1 to 300-500 (I haven't set the limit yet). I will be running a drawing were 10 numbers will be picked at random from the given range. Here's the tricky part: I want some numbers to be less likely to be drawn up. A small set of those 300-500 will be flagged as "lucky numbers". For example, out of 100 drawings, most numbers have equal chances of being drawn, except for a few, that will only be picked once every 30-50 drawings. Basically I need to artificially set the probability of certain numbers to be picked while maintaining an even distribution with the rest of the numbers. The only similar thing I've found so far is this question: Generate A Weighted Random Number, the problem being that my spec has considerably more numbers (up to 500) so the weights would get very small and supposedly this could be a problem with that solution (Rejection Sampling). I'm still trying it, though, but I wonder if there other solutions. Math is not my thing so I appreciate any input. Thanks.

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  • Memory management of objects returned by methods (iOS / Objective-C)

    - by iOSNewb
    I am learning Objective-C and iOS programming through the terrific iTunesU course posted by Stanford (http://www.stanford.edu/class/cs193p/cgi-bin/drupal/) Assignment 2 is to create a calculator with variable buttons. The chain of commands (e.g. 3+x-y) is stored in a NSMutableArray as "anExpression", and then we sub in random values for x and y based on an NSDictionary to get a solution. This part of the assignment is tripping me up: The final two [methods] “convert” anExpression to/from a property list: + (id)propertyListForExpression:(id)anExpression; + (id)expressionForPropertyList:(id)propertyList; You’ll remember from lecture that a property list is just any combination of NSArray, NSDictionary, NSString, NSNumber, etc., so why do we even need this method since anExpression is already a property list? (Since the expressions we build are NSMutableArrays that contain only NSString and NSNumber objects, they are, indeed, already property lists.) Well, because the caller of our API has no idea that anExpression is a property list. That’s an internal implementation detail we have chosen not to expose to callers. Even so, you may think, the implementation of these two methods is easy because anExpression is already a property list so we can just return the argument right back, right? Well, yes and no. The memory management on this one is a bit tricky. We’ll leave it up to you to figure out. Give it your best shot. Obviously, I am missing something with respect to memory management because I don't see why I can't just return the passed arguments right back. Thanks in advance for any answers!

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  • VB.Net - Launch app on Windows startup

    - by Queops
    We all now the tricky folders where your application runs when you publish your VB.NET to other people, but I won't give up on the benefits of the system (auto-update, you know). Problem is: Program is supposed to startup, or not, with Windows if the user wishes so. I'm saving program preferences into My.Settings. All fine with that. If you debug it it will save the values between sessions. The problem is after deployment. I installed the program on a testing machine. Application works okay, the settings load, if it's the user launching it by themselfs (using shortcut on desktop for example). Now upon restarting the program does indeed start up as I want it to but the My.Settings don't show up! It's like the config file has been erased. If I close program and re-open by clicking shorcut it loads the settings just fine though. So I wonder what's the problem? This is the code I use to save the registry key: regKey = Registry.CurrentUser.OpenSubKey("SOFTWARE\Microsoft\Windows\CurrentVersion\Run", True) regKey.SetValue("ScapeTracker", Chr(34) & Application.ExecutablePath & Chr(34) & " startup") Does what it's supposed to. The startup parameter is needed so the program knows if it's launched on startup on not (to show up on tray and idle there until user decides to use it). So the problem is that I can't use the settings upon restart of Windows, so I'm assuming the VB.Net applications have some extra parameters when launching? How can I solve this?

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  • How to systematically generate images from data?

    - by adamvickers
    I work for a performing arts nonprofit. We have seating charts for each of the theaters we work with; each seating chart shows the number of sections, the shape of each section, and the number of rows in each section. We'd like to create dynamic seating charts based on this info. We'd like them to look/feel kinda like this: http://www.fansnap.com/tickets/177754-on. But the tricky part is we'd like to be able to store all the info about each theater (the section names, shape/size of each section, and number of rows in each section) as data and then build a system that reads this data and uses it to create a dynamic map. I'm a life-long web developer, but I don't have have any experience with a difficult graphics problem like this. I realize it's a complex problem and I don't expect anyone to give me a complete answer here, but I would love direction on where I should be looking for more info. Is what I'm describing possible? Does this sort of technique have a name? Where can I learn more about how to accomplish this? What software should I use? Any info would be helpful.

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