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  • How do I return an array from a method?

    - by dwwilson66
    I'm trying to create a deck of cards for my homework. Code is posted below. I need to create four sets of cards (the four suits) and am create a multidimensional array. When I print the results instead of trying to pass the array, I can see that the data in the array is as expected. However, when I try to pass the array card, I get an error cannot find symbol. I've got this modeled after texbook and Java tutorial examples, and I need some help figuring out what I'm missing. I've over-documented to give an idea of how I'm thinking this SHOULD work...please let me know where I've gone horribly wrong in my understanding. import java.util.*; import java.lang.*; // public class CardGame { public static int[][] main(String[] args) { int[][] startDeck = deckOfCards(); /* cast new deck as int[][], calling method deckOfCards System.out.println(" /// from array: " + Arrays.deepToString(startDeck)); } public static int[][] deckOfCards() /* method to return a multi-dimensional array */ { int rank; int suit; for(rank=1;rank<14;rank++) /* cards 1 - 13 .... */ { for(suit=1;suit<5;suit++) /* suits 1 - 4 .... */ { int[][] card = new int[][] /* define a new card... */ { {rank,suit} /* with rank/suit from for... loops */ }; System.out.println(" /// from array: " + Arrays.deepToString(card)); } } return card; /* Error: cannot find symbol } }

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  • Sampling Duplicates

    - by user3640982
    I have a dataset from which I need to sample. It is set up with an ID field and a year field. I want every record from the most current year and then I want the most current ID's but sampled from every 3rd year going back. The data is ordered by year. For example ID<-rep(1:3, 5) Year<-rep(c(1,2,3,4,5),each=3) df<-data.frame(ID,Year) ID Year 1 1 1 2 2 1 3 3 1 4 1 2 5 2 2 6 3 2 7 1 3 8 2 3 9 3 3 10 1 4 11 2 4 12 3 4 13 1 5 14 2 5 15 3 5 So from this example, I would want to return ID Year 1 1 1 2 2 1 3 3 1 4 1 4 5 2 4 6 3 4 I'm thinking that some combination of duplicated() and which() should get what I want, but the problem is duplicated() just tells if it has been repeated; it doesn't say which record is being repeated. which(duplicated(df$ID)) [1] 4 5 6 7 8 9 10 11 12 13 14 15 This a problem since not every ID exists in every year. Any help would be appreciated. Thanks, Eric

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  • TFS: Choose which Team Project to add a solution too.

    - by Patricker
    I have a solution which I developed in VS2008 and which I am trying to add to Source Control (TFS 2010, though the issue happened in TFS 2008 as well). I have several TFS workspaces on my computer and I have access to several Team Projects. When I right click the solution in my Solution Explorer and choose the "Add Solution to Source Control" option I am never given an option of choosing which Workspace or which Team Project to add the existing solution too. VS2008 then proceeds to add it to the same team project every time. I have tried selecting an alternate workspace/team project in every window where I can see an option for it but it always adds it back to the same one. I even tried changing the name of my new workspace so that alphabetically it was the first thinking that it might be somehow related to that... no luck. I then tried goign to the Change Source Control window where you can add/remove bindings on a solution/project but that window also defaults to the same Team Project as trying to add the solution directly does... Any help would be greatly appreciated with this, maybe I'm just missing something?

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  • Rails uploaded file blank

    - by Ceilingfish
    Hi chaps, I'm trying to upload a file to the server using a HTTP multipart form in rails, and for some reason it's turning up blank at the other end. I can see it being received in the rails log thusly: Processing Admin::HeadlinesController#update (for 127.0.0.1 at 2010-03-08 12:26:13) [PUT] Parameters: {"commit"=>"Save changes", "action"=>"update", "_method"=>"put", "authenticity_token"=>"mK70XRk5gOPUwXOcNboT/4K8PD9RBM7GqCOlEUKZwcA=", "headline"=>{"position"=>"1", "location"=>"primary", "attachment_id"=>"13", "headline_content"=>"questionnaires", "article_id"=>"3", "image"=>#<File:/tmp/RackMultipart20100308-63211-1vym9nj-0>}, "id"=>"140", "controller"=>"admin/headlines"} But if I have a look in /tmp/RackMultipart20100308-63211-1vym9nj-0 the file is blank. Am I right in thinking that this should be the file that I uploaded? I'm running Phusion Passenger 2.2.7 on Apache 2.2.13, with ruby 1.8.7 and rails 2.3.5, on OSX 10.6.2

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  • Access class instance "name" dynamically in Python

    - by user328317
    In plain english: I am creating class instances dynamically in a for loop, the class then defines a few attributes for the instance. I need to later be able to look up those values in another for loop. Sample code: class A: def init(self, name, attr): self.name=name self.attr=attr names=("a1", "a2", "a3") x=10 for name in names: name=A(name, x) x += 1 ... ... ... for name in names: print name.attr How can I create an identifier for these instances so they can be accessed later on by "name"? I've figured a way to get this by associating "name" with the memory location: class A: instances=[] names=[] def init(self, name, attr): self.name=name self.attr=attr A.instances.append(self) A.names.append(name) names=("a1", "a2", "a3") x=10 for name in names: name=A(name, x) x += 1 ... ... ... for name in names: index=A.names.index(name) print "name: " + name print "att: " + str(A.instances[index].att) This has had me scouring the web for 2 days now, and I have not been able to find an answer. Maybe I don't know how to ask the question properly, or maybe it can't be done (as many other posts seemed to be suggesting). Now this 2nd example works, and for now I will use it. I'm just thinking there has to be an easier way than creating your own makeshift dictionary of index numbers and I'm hoping I didn't waste 2 days looking for an answer that doesn't exist. Anyone have anything? Thanks in advance, Andy Update: A coworker just showed me what he thinks is the simplest way and that is to make an actual dictionary of class instances using the instance "name" as the key.

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  • Extract domain from body of email

    - by iman453
    Hi, I was wondering if there is any way I could extract domain names from the body of email messages in python. I was thinking of using regular expressions, but I am not too great in writing them, and was wondering if someone could help me out. Here's a sample email body: <tr><td colspan="5"><font face="verdana" size="4" color="#999999"><b>Resource Links - </b></font><span class="snv"><a href="http://clk.about.com/?zi=4/RZ">Get Listed Here</a></span></td><td class="snv" valign="bottom" align="right"><a href="http://sprinks.about.com/faq/index.htm">What Is This?</a></td></tr><tr><td colspan="6" bgcolor="#999999"><img height="1" width="1"></td></tr><tr><td colspan="6"><map name="sgmap"><area href="http://x.about.com/sg/r/3412.htm?p=0&amp;ref=fooddrinksl_sg" shape="rect" coords="0, 0, 600, 20"><area href="http://x.about.com/sg/r/3412.htm?p=1&amp;ref=fooddrinksl_sg" shape="rect" coords="0, 55, 600, 75"><area href="http://x.about.com/sg/r/3412.htm?p=2&amp;ref=fooddrinksl_sg" shape="rect" coords="0, 110, 600, 130"></map><img border="0" src="http://z.about.com/sg/sg.gif?cuni=3412" usemap="#sgmap" width="600" height="160"></td></tr><tr><td colspan="6">&nbsp;</td></tr> <tr><td colspan="6"><a name="d"><font face="verdana" size="4" color="#cc0000"><b>Top Picks - </b></font></a><a href="http://slclk.about.com/?zi=1/BAO" class="srvb">Fun Gift Ideas</a><span class="snv"> from your <a href="http://chinesefood.about.com">Chinese Cuisine</a> Guide</span></td></tr><tr><td colspan="6" bgcolor="cc0000"><img height="1" width="1"></td></tr><tr><td colspan="6" class="snv"> So I would need "clk.about.com" etc. Thanks!

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  • Where is the Open Source alternative to WPF?

    - by Evan Plaice
    If we've learned anything from HTML/CSS it's that, declarative languages (like XML) work best to describe User Interfaces because: It's easy to build code preprocessors that can template the code effectively. The code is in a well defined well structured (ideally) format so it's easy to parse. The technology to effectively parse or crawl an XML based source file already exists. The UIs scripted code becomes much simpler and easier to understand. It simple enough that designers are able to design the interface themselves. Programmers suck at creating UIs so it should be made easy enough for designers. I recently took a look at the meat of a WPF application (ie. the XAML) and it looks surprisingly familiar to the declarative language style used in HTML. It's blindingly apparent to me that the current state of desktop UI development is largely fractionalized, otherwise there wouldn't be so much duplicated effort in the domain of user interfaces (IE. GTK, XUL, Qt, Winforms, WPF, etc). There are 45 GUI platforms for Python alone It's painfully obvious to me that there should be a general purpose, open source, standardized, platform independent, markup language for designing desktop GUIs. Much like what the W3C made HTML/CSS into. WPF, or more specifically XAML seems like a pretty likely step in the right direction. Why hasn't anyone in the Open Source community (AFAIK) even scratched the surface of this issue. Now that the 'browser wars' are over should we look forward to a future of 'desktop gui wars?' Note: This topic is relatively subjective in the attempt to be 'future-thinking.' I think that desktop GUI development in its current state sucks ((really)hard) and, even though WPF is still in it's infancy, it presents a likely solution to the problem. Has no one in the OS community looked into developing something similar because they don't see the value, or because it's not worth the effort?

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  • How to use a getter with a nullable?

    - by Desmond Lost
    I am reading a bunch of queries from a database. I had an issue with the queries not closing, so I added a CommandTimeout. Now, the individual queries read from the config file each time they are run. How would I make the code cache the int from the config file only once using a static nullable and getter. I was thinking of doing something along the lines of: static int? var; get{ var = null; if (var.HasValue) ...(i dont know how to complete the rest) My actual code: private object ExecuteQuery(string dbConnStr, bool fixIt) { object result = false; using (SqlConnection connection = new SqlConnection(dbConnStr)) { connection.Open(); using (SqlCommand sqlCmd = new SqlCommand()) { AddSQLParms(sqlCmd); sqlCmd.CommandTimeout = 30; sqlCmd.CommandText = _cmdText; sqlCmd.Connection = connection; sqlCmd.CommandType = System.Data.CommandType.Text; sqlCmd.ExecuteNonQuery(); } connection.Close(); } return result; }}

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  • What constitutes a development environment, and how do you document it?

    - by Joel Coehoorn
    What items go into a software shop's development environment, how do you document it, and what processes do you follow to make changes? I thinking about this from the standpoint where I want to make it easier to bring new hires up to speed quickly by having all this on a checklist we follow when setting them up, and then while I'm at it making it easier for the new hires or existing team members to bring new powerful toolkits and ideas into the environment without disrupting things. I want to keep this platform agnostic, so even though I'm currently at a microsoft shop where Visual Studio would be assumed I'll go ahead and list compiler/IDE as one of the items: Here are some ideas for part 1: [edit]: I'm keeping this updated based on the better suggestions. Source Control access Issue/Bug/Project tracker System Documention, or references to find the system documentation in source control or in a wiki, including: build document/environment covered by this question design documents / technical notes Coding Style guidelines Deploy for review/testing/QA/staging/production procedures Licensing details for your tools and your product Team Calendar, including the project schedule(s), deadlines, vacation time, and support/on-call schedule (if required) compiler/IDE compiler/IDE extensions (things like source control plugins or visual studio add-ins) 3rd party SDKs/toolkits Database connection and tools Testing Frameworks Internal libraries communication tools (chat, wiki, etc) Static analysis tools (FxCop, FlawFinder, etc) Virtual machines (holding dev environment or for testing) Specialized editors (modeling, xml, etc) Other tools What else goes in this list, and how do you document it and vet changes?

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  • JTA or LOCAL transactions in JPA2+Hibernate 3.6.0?

    - by Pangea
    We are in the process of re-thinking our tech stack and below are our choices (We can't live without Spring and Hibernate due to the complexity etc of the app). We are also moving from J2EE 1.4 to JEE 5. Tech stack JEE 5 JPA 2.0 (I know JEE 5 only supports JPA 1.0 but we want to use Hibernate as the JPA provider) Hibernate 3.6.0 (We already have lots of hbm files with custom types etc. so we doesn't want to migrate them at this time to JPA. This means we want both jpa/hbm mappings work together and hence the Hibernate as the JPA provider instead of using the default that comes with App Server) Now the problems is that I want to stick with local transactions but other team members want to use JTA. I have been working with J2EE for last 9 years and I've heard time and again people suggesting to stick with local transactions if I doesn't need two phase commits. This is not only for performance reasons but debugging/troubleshooting a local transaction is lot easier than a distributed transaction. My suggestion is to use spring declarative transaction management + local transactions (HibernateTransactionManager) I want to make sure if I am being paranoid or I have a valid point. I'd like to hear what the rest of the JEE world thinks. Thank you.

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  • Byte-Pairing for data compression

    - by user1669533
    Question about Byte-Pairing for data compression. If byte pairing converts two byte values to a single byte value, splitting the file in half, then taking a gig file and recusing it 16 times shrinks it to 62,500,000. My question is, is byte-pairing really efficient? Is the creation of a 5,000,000 iteration loop, to be conservative, efficient? I would like some feed back on and some incisive opinions please. Dave, what I read was: "The US patent office no longer grants patents on perpetual motion machines, but has recently granted at least two patents on a mathematically impossible process: compression of truly random data." I was not inferring the Patent Office was actually considering what I am inquiring about. I was merely commenting on the notion of a "mathematically impossible process." If someone has, in some way created a method of having a "single" data byte as a placeholder of 8 individual bytes of data, that would be a consideration for a patent. Now, about the mathematically impossibility of an 8 to 1 compression method, it is not so much a mathematically impossibility, but a series of rules and conditions that can be created. As long as there is the rule of 8 or 16 bit representation of storing data on a medium, there are ways to manipulate data that mirrors current methods, or creation by a new way of thinking.

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  • Making a simple searchable directory of people and their skills in a day - Which technologies?

    - by gav
    Hi All, I am working with a small theatre company. Currently they have a list of people on paper with notes about their skills next to each one. I want to create a database / directory for them so that they can add, delete, update and search for people. It is a very simple and common scenario I know but the issue here is that I only have a day to build a working solution. The search has to be very simple At first I was thinking LAMP but I'd rather not have to create it all from scratch and host it myself. That lead me to Google Spreadsheet as a database, this has the advantage that they already use google docs for everything and if my front end goes tits up they can still get to the data. Presuming none of you can think of some existing software which does exactly what I want the next step is to make a front end for the database. You can create forms for Google Spreadsheets but they only let you add new entries, I can make a Google Gadget but that will only let me implement the search as the Google Visualisation API provides read only access. It's at this point I'm stuck, should I just create a Java Servlet front end for the Google Spreadsheet and use the Java API to add, search and update? I know this is a broad question but I'm just asking 'What would you do?' to implement this system with a day's development time? Gav

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  • Multiple forms using Rails & jQuery & AJAX

    - by biggie8199
    I have multiple coupons on a page and I'm trying to get comments to work on each coupon. So for each coupon i have a comments form. Im using jQuery + Ajax to accomplish this. Here's what my code looks like. Coupon Page <p>Comments:</p> <% form_for(@comment) do |f| %> <%= f.label :body %><br /><%= f.text_field :body, :size => "24" %> <%= f.hidden_field :coupon_id, :value => coupon.id %> <%= f.submit "Save" %> <% end %> Application.js jQuery.ajaxSetup({ 'beforeSend': function(xhr) {xhr.setRequestHeader("Accept", "text/javascript")} }) jQuery.fn.submitWithAjax = function() { this.submit(function() { $.post(this.action, $(this).serialize(), null, "script"); return false; }) return this; }; $(document).ready(function() { $("#new_comment").submitWithAjax(); }) I tried changing the jQuery selector to a class $(".new_comment").submitWithAjax(); Thinking that would work, now all the submit buttons work, however it posts only the first form on the page. What can I change to make it so ajax submits the correct form and not the first one?

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  • Array of templated structs

    - by Jakub Mertlik
    I have structs templated by int derived from a Base struct. struct Base { int i; double d; }; template< int N > struct Derv : base { static const int mN = N; }; I need to make an array of Derv< N where N can vary for each struct in that array. I know C/C++ does not allow arrays of objects of different types, but is there a way around this? I was thinking of separating the type information somehow (hints like pointers to Base struct or usage of union spring to my mind, but with all of these I don't know how to store the type information of each array element for usage DURING COMPILE TIME). As you can see, the memory pattern of each Derv< N is the same. I need to access the type of each array element for template specialization later in my code. The general aim of this all is to have a compile-time dispatch mechanism without the need to do a runtime "type switch" somewhere in the code. Thank you.

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • ASP.NET MVC 2 - How do I use an Interface as the Type for a Strongly Typed View

    - by Rake36
    I'd like to keep my concrete classes separate from my views. Without using strongly typed views, I'm fine. I just use a big parameter list in the controller method signatures and then use my service layer factory methods to create my concrete objects. This is actually just fine with me, but it got me thinking and after a little playing, I realized it was literally impossible for a controller method to accept an interface as a method parameter - because it has no way of instantiating it. Can't create a strongly-typed view using an interface through the IDE either (which makes sense actually). So my question. Is there some way to tell the controller how to instantiate the interface parameter using my service layer factory methods? I'd like to convert from: [Authorize] [AcceptVerbs(HttpVerbs.Post)] [UrlRoute(Path = "Application/Edit/{id}")] public ActionResult Edit(String id, String TypeCode, String TimeCode, String[] SelectedSchoolSystems, String PositionChoice1, String PositionChoice2, String PositionChoice3, String Reason, String LocationPreference, String AvailableDate, String RecipientsNotSelected, String RecipientsSelected) { //New blank app IApplication _application = ApplicationService.GetById(id); to something like [Authorize] [AcceptVerbs(HttpVerbs.Post)] [UrlRoute(Path = "Application/Edit/{id}")] public ActionResult Edit(String id, IApplication app) { //Don't need to do this anymore //IApplication _application = ApplicationService.GetById(id);

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  • How to efficiently convert String, integer, double, datetime to binary and vica versa?

    - by Ben
    Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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  • properly format postal address with line breaks [google maps]

    - by munchybunch
    Using V3 of the google maps API, is there any reliable way to format addresses with the line break? By this, I mean something like 1600 Amphitheatre Parkway Mountain View, CA 94043 should be formatted as 1600 Amphitheatre Parkway Mountain View, CA 94043 Looking through the response object from geocoding, there is an address_components array that has, for the above address, 8 components (not all of the components are used for the address): 0: Object long_name: "1600" short_name: "1600" types: Array[1] 0: "street_number" length: 1 1: Object long_name: "Amphitheatre Pkwy" short_name: "Amphitheatre Pkwy" types: Array[1] 0: "route" length: 1 2: Object long_name: "Mountain View" short_name: "Mountain View" types: Array[2] 0: "locality" 1: "political" length: 2 3: Object long_name: "San Jose" short_name: "San Jose" types: Array[2] 0: "administrative_area_level_3" 1: "political" length: 2 4: Object long_name: "Santa Clara" short_name: "Santa Clara" types: Array[2] 0: "administrative_area_level_2" 1: "political" length: 2 5: Object long_name: "California" short_name: "CA" types: Array[2] 0: "administrative_area_level_1" 1: "political" length: 2 6: Object long_name: "United States" short_name: "US" types: Array[2] 0: "country" 1: "political" length: 2 7: Object long_name: "94043" short_name: "94043" types: Array[1] 0: "postal_code" length: 1 I was thinking that you could just combine parts that you want, like sprintf("%s %s<br />%s, %s %s", array[0].short_name, array[1].short_name, array[2].short_name, array[5].short_name, array[7].short_name) [edit]I just realized that sprintf isn't defined by default in JavaScript, so just a concatenation would do I guess.[/edit] But that seems awfully unreliable. Does anyone know the details on the structure of address_components, and if it's reliably similar like that for street addresses in the US? If I wanted to, I guess I could look for the proper types (street_number,route, etc) as well. I'd love it if anyone had a better way than what I"m doing here...

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  • Strategy game programming in Java, how the map and unit classes should work/relate each other.

    - by Gabriel A. Zorrilla
    As a way of learning Java i'm doing a little strategy game. You have a game map and military units. The gamemap and the units are Jpanels which are binded together in another class called GameWindow, which has a JLayeredPane where the gamepap is below the units. Every time i click a unit (and therefore, the JPane) I can get the unit's information. The problem comes when i want to move a unit... each unit is self drawn inside it's Jpanel, how do i represent the change in position over the gamemap? I'm thinking about reloading the whole game window based on a position change of a unit (because the JPAnels that represent the units are created in the GameWindow, not drawn in the gamemap). Another more elegant option, should be repainting the whole map, with the units. But that way the units would lose it's status of objects (no more JPAnels, just being drawn in the gamemap paint() method), and how would i tell if one unit is clicked? I dont know how people with more experience in games handle the class structure in strategy games. I believe i have the right structure (map, game units, each one an object) but I'm having difficulties making it work together. Here is a snapshot of the map with a couple of units:

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  • Silverlight 4 ComboBox - Binding to Nullable data (tried TargetNullValue but not working as expected)

    - by Laurence
    (Please note - I am a Silverlight beginner and am looking for the simplest solution here, e.g. that doesn't involve writing/installing a replacement for the ComboBox control!) This is an issue with a Silverlight 4 application that uses the View Model (MVVM) approach. I have a simple form for editing a "Product" object. Product has a CategoryID property which is nullable (int?). A ComboBox is used to view and set the CategoryID - this is bound to an ObservableCollection of Categories. Product also has number of non-nullable properties bound to TextBoxes. I want the user to see "N/A" in the ComboBox for a product with no category, and to be use this "N/A" option to set CategoryID to null. So, I manually added a Category object with CategoryID=0 and CategoryName="N/A" to the collection; then I set TargetNullValue=0 in the SelectedValue Binding of the ComboBox. My thinking was - when the ComboBox SelectedValue was bound to a null CategoryID it would substitute zero, and therefore select the "N/A" option. When editing a Product with a non-null CategoryID, everything works. However when a null CategoryID is found, two problems occur: No option is selected in the ComboBox (its blank) The ComboBox binding seems broken from this point onwards - any Product I subsequently edit (incl. ones with a non-null CategoryID) have nothing selected in the ComboBox (its still populated with all categories - just no selected item). I've seen reports of problem #2 (here, here) but I was under the impression that #1 should have worked. What am I missing to get the "N/A" option to be selected? XAML for ComboBox: <ComboBox x:Name="cboCategory" ItemsSource="{Binding colCategories, Mode=OneWay}" SelectedValuePath="CategoryID" DisplayMemberPath="CategoryName" SelectedValue="{Binding CurrentProduct.CategoryID, Mode=TwoWay, TargetNullValue=0}" Height="24" Width="344"></ComboBox>

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  • Field Members vs Method Variables?

    - by Braveyard
    Recently I've been thinking about performance difference between class field members and method variables. What exactly I mean is in the example below : Lets say we have a DataContext object for Linq2SQL class DataLayer { ProductDataContext context = new ProductDataContext(); public IQueryable<Product> GetData() { return context.Where(t=>t.ProductId == 2); } } In the example above, context will be stored in heap and the GetData method variables will be removed from Stack after Method is executed. So lets examine the following example to make a distinction : class DataLayer { public IQueryable<Product> GetData() { ProductDataContext context = new ProductDataContext(); return context.Where(t=>t.ProductId == 2); } } (*1) So okay first thing we know is if we define ProductDataContext instance as a field, we can reach it everywhere in the class which means we don't have to create same object instance all the time. But lets say we are talking about Asp.NET and once the users press submit button the post data is sent to the server and the events are executed and the posted data stored in a database via the method above so it is probable that the same user can send different data after one another.If I know correctly after the page is executed, the finalizers come into play and clear things from memory (from heap) and that means we lose our instance variables from memory as well and after another post, DataContext should be created once again for the new page cycle. So it seems the only benefit of declaring it publicly to the whole class is the just number one text above. Or is there something other? Thanks in advance... (If I told something incorrect please fix me.. )

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  • The following grammar is LL1, SLR, LR(1), LALR?

    - by Mike
    P - {D ; C} D - d; D| d C - c; C | c a) Is the grammar LL(1)? Explain your answer. b) Is the grammar SLR(1)? Explain your answer. c) Is the grammar LR(1)? Explain your answer. d) Is the grammar LALR? Explain your answer. As for my answers I actually got no for them all... so I'm thinking I did something wrong Here is my explanation. a) It is not LL(1) because it is not left factored. b) It is not SLR, because of the transition diagram item 2 ( which is... ) D- d . ; D D- d . We need to consult the follow set, Follow(D) = ; Therefore this is not SLR c) It is not LR(1) because of... item 1 P- {D.;C} , $ D- .d;D , ; D- .d , ; item 2 D- d.; D , ; D- d. , ; item 3 D- d; . D , ; D- .d;D , ; D- .d , ; Since item 2 goes to item 3 with ;, AND "D- d."'s (in item 2) look ahead token is also ;. this causes a reduce to shift conflict, therefore this grammar is not LR(1) d) This grammar is not LALR because it is not LR(1) Thanks for your help!

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  • Generic callbacks

    - by bobobobo
    Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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  • Group / User based security. Table / SQL question

    - by Brett
    Hi, I'm setting up a group / user based security system. I have 4 tables as follows: user groups group_user_mappings acl where acl is the mapping between an item_id and either a group or a user. The way I've done the acl table, I have 3 columns of note (actually 4th one as an auto-id, but that is irrelevant) col 1 item_id (item to access) col 3 user_id (user that is allowed to access) col 3 group_id (group that is allowed to access) So for example item1, peter, , item2, , group1 item3, jane, , so either the acl will give access to a user or a group. Any one line in the ACL table with either have an item - user mapping, or an item group. If I want to have a query that returns all objects a user has access to, I think I need to have a SQL query with a UNION, because I need 2 separate queries that join like.. item - acl - group - user AND item - acl - user This I guess will work OK. Is this how its normally done? Am I doing this the right way? Seems a little messy. I was thinking I could get around it by creating a single user group for each person, so I only ever deal with groups in my SQL, but this seems a little messy as well..

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  • A good solution for displaying galleries with lytebox and php

    - by Johann
    Hello I have thought for a while over an issue with the loading of images on a website-solution that I have programmed (For fun and the experience) The programming language used is PHP with MYSQL as the database language It also uses javascript, but not extensively I have recently realized that the engine I programmed, while it has it's smart solutions also carry a lot of flaws and redundant code. I have therefore decided to make a new one, now incorporating what I know, but didn't when I started the previous project. For the new system, there will be an option to add galleries to a site, and upload images to it. I have used the javascript image viewer Lytebox before. The screen goes dark and an image appears with a "Previous" and "next" button to view the other images. The problem is that I used groups with lytebox and the images themselves, resized as thumbs. This causes lytebox to work only when all the images have loaded. If you click a link before that, the image is shown as if you right click and choose "Show image" Information about these images is parsed from a database using a while statement with a counter that goes from 0 to sizeof() I'm thinking it probably isn't a good idea to have the images as the thumbs, even if you restrict the upload size. Likewise, adding thumbs at upload also seems like a hassle. It would be practical if the thumbs didn't show up before they were fully loaded. Has anyone got any good tips. Any help would be appreciated. Johann

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