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• Program Structure Design Tools? (Top Down Design)

  - by Lee Olayvar

  I have been looking to expand my methodologies to better involve Unit testing, and i stumbled upon Behavioral Driven Design (Namely Cucumber, and a few others). I am quite intrigued by the concept as i have never been able to properly design top down, only because keeping track of the design gets lost without a decent way to record it. So on that note, in a mostly language agnostic way, are there any useful tools out there i am (probably) unaware of? Eg, i have often been tempted to try building flow charts for my programs, but i am not sure how much that will help, and it seems a bit confusing to me how i could make a complex enough flow chart to handle the logic of a full program, and all its features.. ie, it just seems like flow charts would be limiting in the design scheme.. or possibly grow to an unmaintainable scale. BDD methods are nice, but with a system that is so tied to structure, tying into the language and unit testing seems like a must (for it to be worth it) and it seems to be hard to find something to work well with both Python and Java (my two main languages). So anyway.. on that note, any comments are much appreciated. I have searched around on here and it seems like top down design is a well discussed topic, but i haven't seen too much reference to tools themselves, eg, flow chart programs, etc. I am on Linux, if it matters (in the case of programs).

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• Convert function to read from string instead of file in C

  - by Dusty

  I've been tasked with updating a function which currently reads in a configuration file from disk and populates a structure: static int LoadFromFile(FILE *Stream, ConfigStructure *cs) { int tempInt; ... if ( fscanf( Stream, "Version: %d\n",&tempInt) != 1 ) { printf("Unable to read version number\n"); return 0; } cs->Version = tempInt; ... } to one which allows us to bypass writing the configuration to disk and instead pass it directly in memory, roughly equivalent to this: static int LoadFromString(char *Stream, ConfigStructure *cs) A few things to note: The current LoadFromFile function is incredibly dense and complex, reading dozens of versions of the config file in a backward compatible manner, which makes duplication of the overall logic quite a pain. The functions that generate the config file and those that read it originate in totally different parts of the old system and therefore don't share any data structures so I can't pass those directly. I could potentially write a wrapper, but again, it would need to handle any structure passed in in a backwards compatible manner. I'm tempted to just pass the file as is in as a string (as in the prototype above) and convert all the fscanf's to sscanf's but then I have to handle incrementing the pointer along (and potentially dealing with buffer overrun errors) manually. This has to remain in C, so no C++ functionality like streams can help here Am I missing a better option? Is there some way to create a FILE * that actually just points to a location in memory instead of on disk? Any pointers, suggestions or other help is greatly appreciated.

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• How to debug anomalous C memory/stack problems

  - by EBM

  Hello, Sorry I can't be specific with code, but the problems I am seeing are anomalous. Character string values seem to be getting changed depending on other, unrelated code. For example, the value of the argument that is passed around below will change merely depending on if I comment out one or two of the fprintf() calls! By the last fprintf() the value is typically completely empty (and no, I have checked to make sure I am not modifying the argument directly... all I have to do is comment out a fprintf() or add another fprintf() and the value of the string will change at certain points!): static process_args(char *arg) { /* debug */ fprintf(stderr, "Function arg is %s\n", arg); ...do a bunch of stuff including call another function that uses alloc()... /* debug */ fprintf(stderr, "Function arg is now %s\n", arg); } int main(int argc, char *argv[]) { char *my_arg; ... do a bunch of stuff ... /* just to show you it's nothing to do with the argv array */ my_string = strdup(argv[1]); /* debug */ fprintf(stderr, "Argument 1 is %s\n", my_string); process_args(my_string); } There's more code all around, so I can't ask for someone to debug my program -- what I want to know is HOW can I debug why character strings like this are getting their memory changed or overwritten based on unrelated code. Is my memory limited? My stack too small? How do I tell? What else can I do to track down the issue? My program isn't huge, it's like a thousand lines of code give or take and a couple dynamically linked external libs, but nothing out of the ordinary. HELP! TIA!

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• Banning by IP with php/mysql

  - by incrediman

  I want to be able to ban users by IP. My idea is to keep a list of IP's as rows in an BannedIPs table (the IP column would be an index). To check users' IP's against the table, I will keep a session variable called $_SESSION['IP'] for each session. If on any request, $_SESSION['IP'] doesn't match $_SERVER['REMOTE_ADDR'], I will update $_SESSION['IP'] and check the BannedIPs table to see if the IP is banned. (A flag will also be saved as a session variable specifying whether or not the user is banned) Here are the things I'm wondering: Does that sound like a good strategy with regards to speed and security (would someone be able to get around the IP ban somehow, other than changing IP's)? What's the best way to structure a mysql query that checks to see if a row exists? That is, what's the best way to query the db to see if a row with a certain IP exists (to check if it's banned)? Should I save the IP's as integers or strings? Note that... I estimate there will be between 1,000-10,000 banned IP's stored in the database. $_SERVER['REMOTE_ADDR'] is the IP from which the current request was sent.

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• haskell: a data structure for storing ascending integers with a very fast lookup

  - by valya

  Hello! (This question is related to my previous question, or rather to my answer to it.) I want to store all qubes of natural numbers in a structure and look up specific integers to see if they are perfect cubes. For example, cubes = map (\x -> x*x*x) [1..] is_cube n = n == (head $ dropWhile (<n) cubes) It is much faster than calculating the cube root, but It has complexity of O(n^(1/3)) (am I right?). I think, using a more complex data structure would be better. For example, in C I could store a length of an already generated array (not list - for faster indexing) and do a binary search. It would be O(log n) with lower ?oefficient than in another answer to that question. The problem is, I can't express it in Haskell (and I don't think I should). Or I can use a hash function (like mod). But I think it would be much more memory consuming to have several lists (or a list of lists), and it won't lower the complexity of lookup (still O(n^(1/3))), only a coefficient. I thought about a kind of a tree, but without any clever ideas (sadly I've never studied CS). I think, the fact that all integers are ascending will make my tree ill-balanced for lookups. And I'm pretty sure this fact about ascending integers can be a great advantage for lookups, but I don't know how to use it properly (see my first solution which I can't express in Haskell).

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• Perl program - Dynamic Bootstrapping code

  - by mgj

  Hi.. I need to understand the working of this particular program, It seems to be quite complicated, could you please see if you could help me understanding what this program in Perl does, I am a beginner so I hardly can understand whats happening in the code given on the following link below, Any kind of guidance or insights wrt this program is highly appreciated. Thank you...:) This program is called premove.pl.c Its associated with one more program premove.pl, Its code looks like this: #!perl open (newdata,">newdata.txt") || die("cant create new file\n");#create passwd file $linedata = ""; while($line=<>){ chomp($line); #chop($line); print newdata $line."\n"; } close(newdata); close(olddata); __END__ I am even not sure how to run the two programs mentioned here. I wonder also what does the extension of the first program signify as it has "pl.c" extension, please let me know if you know what it could mean. I need to understand it asap thats why I am posting this question, I am kind of short of time else I would try to figure it out myself, This seems to be a complex program for a beginner like me, hope you understand. Thank you again for your time.

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• How you would you describe the Observer pattern in beginner language?

  - by Sheldon

  Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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• change custom mapping - sharp architecture/ fluent nhibernate

  - by csetzkorn

  I am using the sharp architecture which also deploys FNH. The db schema sql code is generated during the testing like this: [TestFixture] [Category("DB Tests")] public class MappingIntegrationTests { [SetUp] public virtual void SetUp() { string[] mappingAssemblies = RepositoryTestsHelper.GetMappingAssemblies(); configuration = NHibernateSession.Init( new SimpleSessionStorage(), mappingAssemblies, new AutoPersistenceModelGenerator().Generate(), "../../../../app/XXX.Web/NHibernate.config"); } [TearDown] public virtual void TearDown() { NHibernateSession.CloseAllSessions(); NHibernateSession.Reset(); } [Test] public void CanConfirmDatabaseMatchesMappings() { var allClassMetadata = NHibernateSession.GetDefaultSessionFactory().GetAllClassMetadata(); foreach (var entry in allClassMetadata) { NHibernateSession.Current.CreateCriteria(entry.Value.GetMappedClass(EntityMode.Poco)) .SetMaxResults(0).List(); } } /// <summary> /// Generates and outputs the database schema SQL to the console /// </summary> [Test] public void CanGenerateDatabaseSchema() { System.IO.TextWriter writeFile = new StreamWriter(@"d:/XXXSqlCreate.sql"); var session = NHibernateSession.GetDefaultSessionFactory().OpenSession(); new SchemaExport(configuration).Execute(true, false, false, session.Connection, writeFile); } private Configuration configuration; } I am trying to use: using FluentNHibernate.Automapping; using xxx.Core; using SharpArch.Data.NHibernate.FluentNHibernate; using FluentNHibernate.Automapping.Alterations; namespace xxx.Data.NHibernateMaps { public class x : IAutoMappingOverride<x> { public void Override(AutoMapping<Tx> mapping) { mapping.Map(x => x.text, "text").CustomSqlType("varchar(max)"); mapping.Map(x => x.url, "url").CustomSqlType("varchar(max)"); } } } To change the standard mapping of strings from NVARCHAR(255) to varchar(max). This is not picked up during the sql schema generation. I also tried: mapping.Map(x = x.text, "text").Length(100000); Any ideas? Thanks. Christian

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• What ever happened to APL?

  - by lkessler

  When I was at University 30 years ago, I used a programming language called APL. I believe the acronym stood for "A Programming Language", This language was interpretive and was especially useful for array and matrix operations with powerful operators and library functions to help with that. Did you use APL? Is this language still in use anywhere? Is it still available, either commercially or open source? I remember the combinatorics assignment we had. It was complex. It took a week of work for people to program it in PL/1 and those programs ranged from 500 to 1000 lines long. I wrote it in APL in under an hour. I left it at 10 lines for readability, although I should have been a purist and worked another hour to get it into 1 line. The PL/1 programs took 1 or 2 minutes to run on the IBM mainframe and solve the problem. The computer charge was $20. My APL program took 2 hours to run and the charge was $1,500 which was paid for by our Computer Science Department's budget. That's when I realized that a week of my time is worth way more than saving some $'s in someone else's budget. I got an A+ in the course. p.s. Don't miss this presentation entitled: "APL one of the greatest programming languages ever"

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• Write binary data as a response in an ASP.NET MVC web control

  - by Lou Franco

  I am trying to get a control that I wrote for ASP.NET to work in an ASP.NET MVC environment. Normally, the control does the normal thing, and that works fine Sometimes it needs to respond by clearing the response, writing an image to the response stream and changing the content type. When you do this, you get an exception "OutputStream is not available when a custom TextWriter is used". If I were a page or controller, I see how I can create custom responses with binary data, but I can't see how to do this from inside a control's render functions. To simplify it -- imagine I want to make a web control that renders to: <img src="pageThatControlIsOn?controlImage"> And I know how to look at incoming requests and recognize query strings that should be routed to the control. Now the control is supposed to respond with a generated image (content-type: image/png -- and the encoded image). In ASP.NET, we: Response.Clear(); Response.OutputStream.Write(thePngData); // this throws in MVC // set the content type, etc Response.End(); How am I supposed to do that in an ASP.NET MVC control?

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• Need Help with SQL Subquery

  - by Pete Augello

  Hey: I am trying to write a query that will return all orders that only have a Subscription included. It is easy enough to write a query that includes all Orders with Subscriptions, another that includes all orders without a Subscription and then compare them with an unmatched query. But I don't want to have to store Queries in my Access database, I prefer to have it all in my ASP code, and I can't get this to work with just one complex query. Here are samples of what works if I store them: Query1 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((Not ((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query2 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query3 SELECT Query2.OrderID, Query2.ProductID FROM Query2 LEFT JOIN Query1 ON Query2.OrderID = Query1.OrderID WHERE (((Query1.OrderID) Is Null)); So, my question is 'how do I write Query3 so that it doesn't refer to Query1 or Query2?' or, am I missing some other way do do this? Thanks, Pete [email protected]

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• How to update QStandartItemModel without freezing the main UI

  - by user1044002

  I'm starting to learn PyQt4 and have been stuck on something for a long time now and can't figure it out myself: Here is the concept: There is a TreeView with custom QStandartItemModel, which gets rebuild every couple of seconds, and can have a lot (hundreds at least) of entries, there also will be additional delegates for the different columns etc. It's fairly complex and the building time for even plain model, without delegates, goes up to .3 sec, which makes the TreeView to freeze. Please advice me for the best approach on solving this. I was thing of somehow building the model in different thread, and eventually sending it to the TreeView, where it would just perform setModel() with the new one, but couldn't make that work. here is some code that may illustrate the problem a bit: from PyQt4.QtCore import * from PyQt4.QtGui import * import sys, os, re, time app = QApplication(sys.argv) REFRESH = 1 class Reloader_Thread(QThread): def __init__(self, parent = None): QThread.__init__(self, parent) self.loaders = ['\\', '--', '|', '/', '--'] self.emit(SIGNAL('refresh')) def run(self): format = '|%d/%b/%Y %H:%M:%S| ' while True: self.emit(SIGNAL('refresh')) self.sleep(REFRESH) class Model(QStandardItemModel): def __init__(self, viewer=None): QStandardItemModel.__init__(self,None) self.build() def build(self): stTime = time.clock() newRows = [] for r in range(1000): row = [] for c in range(12): item = QStandardItem('%s %02d%02d' % (time.strftime('%H"%M\'%S'), r,c)) row.append(item) newRows.append(row) eTime = time.clock() - stTime outStr = 'Build %03f' % eTime format = '|%d/%b/%Y %H:%M:%S| ' stTime = time.clock() self.beginRemoveRows(QModelIndex(), 0, self.rowCount()) self.removeRows(0, self.rowCount()) self.endRemoveRows() eTime = time.clock() - stTime outStr += ', Remove %03f' % eTime stTime = time.clock() numNew = len(newRows) for r in range(numNew): self.appendRow(newRows[r]) eTime = time.clock() - stTime outStr += ', Set %03f' % eTime self.emit(SIGNAL('status'), outStr) self.reset() w = QWidget() w.setGeometry(200,200,800,600) hb = QVBoxLayout(w) tv = QTreeView() tvm = Model(tv) tv.setModel(tvm) sb = QStatusBar() reloader = Reloader_Thread() tvm.connect(tvm, SIGNAL('status'), sb.showMessage) reloader.connect(reloader, SIGNAL('refresh'), tvm.build) reloader.start() hb.addWidget(tv) hb.addWidget(sb) w.show() app.setStyle('plastique') app.processEvents(QEventLoop.AllEvents) app.aboutToQuit.connect(reloader.quit) app.exec_()

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• dynamically horizontal scalable key value store

  - by Zubair

  Hi, Is there a key value store that will give me the following: Allow me to simply add and remove nodes and will redstribute the data automatically Allow me to remove nodes and still have 2 extra data nodes to provide redundancy Allow me to store text or images up to 1GB in size Can store small size data up to 100TB of data Fast (so will allow queries to be performed on top of it) Make all this transparent to the client Works on Ubuntu/FreeBSD or Mac Free or open source I basically want something I can use a "single", and not have to worry about having memcached, a db, and several storage components so yes, I do want a database "silver bullet" you could say. Thanks Zubair Answers so far: MogileFS on top of BackBlaze - As far as I can see this is just a filesystem, and after some research it only seems to be appropriate for large image files Tokyo Tyrant - Needs lightcloud. This doesn't auto scale as you add new nodes. I did look into this and it seems it is very fast for queries which fit onto a single node though Riak - This is one I am looking into myself, but I don't have any results yet Amazon S3 - Is anyone using this as their sole persistance layer in production? From what I have seen it seems to be used for storage of images as complex queries are too expensive @shaman suggested Cassandra - definitely one I am looking into So far it seems that there is no database or key value store that fulfills the criteria I mentioned, not even after offering a bounty of 100 points did the question get answered!

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• Audio stream mangement in Linux

  - by User1

  I have a very complicated audio setup for a project. Here's what we have: 3 applications playing sound 2 applications recording sound 2 sound cards I really don't really have the code to any of these applications. All I want to do is monitor and control the audio streams. Here are a few examples of operations I'd like to do while the applications are running: Mute one of the incoming audio streams. Have one of the incoming audio streams do a "solo" (be the only stream that can "talk"). Get a graph (about 30 seconds worth) of the audio that each stream produced. Send one of the audio streams to soundcard #1, but all three audio streams to soundcard #2. I would likely switch audio streams every 2 minutes or so with one of the operations listed above. A GUI would be preferred. I started looking at the sound systems in Linux and it gets extremely complex and I feel like there have been many new advances in the past few years. I see jack, pulseaudio, artsd, and several other packages. They all have some promise but where should I start? Is there something someone already built that can help?

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• What is Adobe Flex? Is it just Flash II?

  - by Adam Davis

  Question Alright, I'm confused by all the buzzwords and press release bingo going on. What is the relationship between flash and flex: Replace flash (not really compatible) Enhance flash The next version of flash but still basically compatible Separate technology altogether ??? If I'm starting out in Flash now, should I just skip to Flex? Follow up Ok, so what I'm hearing is that there's three different parts to the puzzle: Flash The graphical editor used to make "Flash Movies", ie it's an IDE that focuses on the visual aspect of "Flash" (Officially Flash CS3?) The official name for the display plugins (ie, "Download Flash Now!") A general reference to the entire technology stack In terms of the editor, it's a linear timeline based editor, best used for animations with complex interactivity. Actionscript The "Flash" programming language Flex An Adobe Flash IDE that focuses on the coding/programming aspect of "Flash" (Flex Builder?) A Flash library that enhances Flash and makes it easier to program for (Flex SDK?) Is not bound to a timeline (as the Flash IDE is) and so "standard" applications are more easily accomplished. Is this correct?

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• IValueConverter from string

  - by Aleksandar Toplek

  I have an Enum that needs to be shown in ComboBox. I have managed to get enum values to combobox using ItemsSource and I'm trying to localize them. I thought that that could be done using value converter but as my enum values are already strings compiler throws error that IValueConverter can't take string as input. I'm not aware of any other way to convert them to other string value. Is there some other way to do that (not the localization but conversion)? I'm using this marku extension to get enum values [MarkupExtensionReturnType(typeof (IEnumerable))] public class EnumValuesExtension : MarkupExtension { public EnumValuesExtension() {} public EnumValuesExtension(Type enumType) { this.EnumType = enumType; } [ConstructorArgument("enumType")] public Type EnumType { get; set; } public override object ProvideValue(IServiceProvider serviceProvider) { if (this.EnumType == null) throw new ArgumentException("The enum type is not set"); return Enum.GetValues(this.EnumType); } } and in Window.xaml <Converters:UserTypesToStringConverter x:Key="userTypeToStringConverter" /> .... <ComboBox ItemsSource="{Helpers:EnumValuesExtension Data:UserTypes}" Margin="2" Grid.Row="0" Grid.Column="1" SelectedIndex="0" TabIndex="1" IsTabStop="False"> <ComboBox.ItemTemplate> <DataTemplate DataType="{x:Type Data:UserTypes}"> <Label Content="{Binding Converter=userTypeToStringConverter}" /> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox> And here is converter class, it's just a test class, no localization yet. public class UserTypesToStringConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return (int) ((Data.UserTypes) value) == 0 ? "Fizicka osoba" : "Pravna osoba"; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return default(Data.UserTypes); } }

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• Subclassing an NSTextField

  - by Hooligancat

  Given all the complex things I seem to cover every day, this appears to be a "what the heck am I doing wrong that seems to simple?" scenario! I would like to subclass an NSTextField to change the background color and text color. For simplicity sake (and to help anyone who hasn't ever subclassed anything before), here is the example of my (simplified) subclass MyNSTextFieldSubclass... Step 1: Create the subclass file: First the header file @interface MyTextFieldSubclass : NSTextField { } @end And the method file @implementation MyTextFieldSubclass -(NSColor *)backgroundColor { return [NSColor redColor]; } -(NSColor *)textColor { return [NSColor yellowColor]; } @end Step 2: Drag an NSTextField to a window in Interface Builder, select the Identity tab in the inspector and select the class MyTextFieldSubclass Step 3: Save the IB file, build and run the application Problem When I run the build, the text field does not reflect the color subclassing. However, I know the subclass is being called because if I add the following method, it gets called on text changes. -(void)textDidChange:(NSNotification *)notification { NSLog(@"My text changed"); } So why does the color change not occur on the text fields? I know that I can set the color in IB, but for anyone who has dealt with a lot of UI elements that all need the same styling, subclassing makes life way, way easier. Ironically, I have never had to subclass an NSTextField before and this one has me stumped. As usual, any and all help very much appreciated. I'm sure it will turn out to be a "Doh!" moment - just cant see the wood for the trees right now (plus I'm exhausted from watching too much World Cup Football early in the morning which never helps).

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• Redraw and flicker issues

  - by AngryHacker

  I have an Outlook style app. So basically I have a sidebar on the left and on the right I have a panel control (pnlMainBody) that hosts content. The content is typically a user control that I add to the panel when user clicks appropriate button in the side bar. The way I add the user control to the panel is as follows: // _pnlEmails is the User Control that I am adding to the panel _pnlEmails = new pnlEmails(); _pnlEmails.Dock = DockStyle.Fill; this.pnlMainBody.Controls.Add(_pnlEmails); Some of the user controls that I add to the main panel are quite complex UI-wise. So when this.pnlMainBody.Controls.Add(_pnlEmails); fires, I see the control appear on the screen, then it resizes itself to fill the body of the panel control. It's quite ugly actually, so I was wondering whether there is a way to not show the resizing until it's actually done resizing? I've tried setting the user control's .Visible to false. I've tried doing .SuspendLayout, all to no avail. Is there a way to do this so the screen transitions are smooth?

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• C - Complicated pointer declarations - help understanding

  - by Emmel

  In my burgeoning new self-education in the C language, I've come across a set of declarations that I do not understand how to read. I'd love for someone to break these down. I'll explain at the bottom where I got these examples from. 1. char (*(*x())[])() "x: function returning pointer to array[] of pointer to function returning char" - huh? 2. char (*(*x[3])())[5] "x: array[3] of pointer to function returning pointer to array[5] of char" - come again? 3. char **argv This I understand. "Pointer to pointer to char." But what I don't understand is -- what's the use case for a pointer to a pointer? Follow-up question: does anyone every use declarations this complex or is this just academic fun on the part of the authors of the examples I got this from? These examples are from section 5.12 of the K&R book. This is the first time I'm genuinely stumped by an explanation, in an otherwise well-written classic. Thanks.

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• Hibernate : Opinions in Composite PK vs Surrogate PK

  - by Albert Kam

  As i understand it, whenever i use @Id and @GeneratedValue on a Long field inside JPA/Hibernate entity, i'm actually using a surrogate key, and i think this is a very nice way to define a primary key considering my not-so-good experiences in using composite primary keys, where : there are more than 1 business-value-columns combination that become a unique PK the composite pk values get duplicated across the table details cannot change the business value inside that composite PK I know hibernate can support both types of PK, but im left wondering by my previous chats with experienced colleagues where they said that composite PK is easier to deal with when doing complex SQL queries and stored procedure processes. They went on saying that when using surrogate keys will complicate things when doing joining and there are several condition when it's impossible to do some stuffs when using surrogate keys. Although im sorry i cant explain the detail here since i was not clear enough when they explain it. Maybe i'll put more details next time. Im currently trying to do a project, and want to try out surrogate keys, since it's not getting duplicated across tables, and we can change the business-column values. And when the need for some business value combination uniqueness, i can use something like : @Table(name="MY_TABLE", uniqueConstraints={ @UniqueConstraint(columnNames={"FIRST_NAME", "LAST_NAME"}) // name + lastName combination must be unique But im still in doubt because of the previous discussion about the composite key. Could you share your experiences in this matter ? Thank you !

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• Endless problems with a very simple python subprocess.Popen task

  - by Thomas

  I'd like python to send around a half-million integers in the range 0-255 each to an executable written in C++. This executable will then respond with a few thousand integers. Each on one line. This seems like it should be very simple to do with subprocess but i've had endless troubles. Right now im testing with code: // main() u32 num; std::cin >> num; u8* data = new u8[num]; for (u32 i = 0; i < num; ++i) std::cin >> data[i]; // test output / spit it back out for (u32 i = 0; i < num; ++i) std::cout << data[i] << std::endl; return 0; Building an array of strings ("data"), each like "255\n", in python and then using: output = proc.communicate("".join(data))[0] ...doesn't work (says stdin is closed, maybe too much at one time). Neither has using proc.stdin and proc.stdout worked. This should be so very simple, but I'm getting constant exceptions, and/or no output data returned to me. My Popen is currently: proc = Popen('aux/test_cpp_program', stdin=PIPE, stdout=PIPE, bufsize=1) Advise me before I pull my hair out. ;)

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• Preserving hierarchy when converting .csv file to xml or json

  - by Simon Levinson

  Hello I have a question concerning translating data from a CSV into XML or JSON where it is essential to preserve the heirarchy of the data. For example, if I have CSV data like this: type,brand,country,quantity apple,golden_delicious,english,1 apple,golden_delicious,french,2 apple,cox,,4 apple,braeburn,,1 banana,,carribean,6 banana,,central_america,7 clememtine,,,3 What I want is to preserve hierarchy in the XML so that I get something like: <fruit> <type = "apple"> <brand = "golden_delicious"> <country = "english" quantity = "1"> <country = "french" quantity = "2"> </brand> <brand = "cox"> <quantity = "4"> </brand> <brand = "braeburn"> <quantity = "1"> </brand> </type> <type = "banana"> <country = "carribean" quantity = "6"> <country = "central_america" quantity = "7"> </type> <type = "clementine"> <quantity = "3"> </type> <fruit /> Is it best to try to use JAXP or to convert the above into a table simply of parent, child and then writing the data to an array of strings for processing,? Like this: parent,child fruit,apple apple,golden_delicious golden_delicious,english golden_delicious,french english,1 french,2 apple,cox cox,4 apple,braeburn braeburn,1 And so on. Or is there a better way? Thanks Simon Levinson

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• How to implement properly plugins in C#?

  - by MartyIX

  I'm trying to add plugins to my game and what I'm trying to implement is this: Plugins will be either mine or 3rd party's so I would like a solution where crashing of the plugin would not mean crashing of the main application. Methods of plugins are called very often (for example because of drawing of game objects). What I've found so far: 1) http://www.codeproject.com/KB/cs/pluginsincsharp.aspx - simple concept that seems like it should work nicely. Since plugins are used in my game for every round I would suffice to add the Restart() method and if a plugin is no longer needed Unload() method + GC should take care of that. 2) http://mef.codeplex.com/Wikipage - Managed Extensibility Framework - my program should work on .NET 3.5 and I don't want to add any other framework separately I want to write my plugin system myself. Therefore this solution is out of question. 3) Microsoft provides: http://msdn.microsoft.com/en-us/library/system.addin.aspx but according to a few articles I've read it is very complex. 4) Different AppDomains for plugins. According to Marc Gravell ( http://stackoverflow.com/questions/665668/usage-of-appdomain-in-c ) different AppDomains allow isolation. Unloading of plugins would be easy. What would the performance load be? I need to call methods of plugins very often (to draw objects for example). Using Application Domains - http://msdn.microsoft.com/en-us/library/yb506139.aspx A few tutorials on java2s.com Could you please comment on my findings? New approaches are also welcomed! Thanks!

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• Generics with constraints hierarchy

  - by devoured elysium

  I am currently facing a very disturbing problem: interface IStateSpace<Position, Value> where Position : IPosition // <-- Problem starts here where Value : IValue // <-- and here as I don't { // know how to get away this // circular dependency! // Notice how I should be // defining generics parameters // here but I can't! Value GetStateAt(Position position); void SetStateAt(Position position, State state); } As you'll down here, both IPosition, IValue and IState depend on each other. How am I supposed to get away with this? I can't think of any other design that will circumvent this circular dependency and still describes exactly what I want to do! interface IState<StateSpace, Value> where StateSpace : IStateSpace where Value : IValue { StateSpace StateSpace { get; }; Value Value { get; set; } } interface IPosition { } interface IValue<State> where State : IState { State State { get; } } Basically I have a state space IStateSpace that has states IState inside. Their position in the state space is given by an IPosition. Each state then has one (or more) values IValue. I am simplifying the hierarchy, as it's a bit more complex than described. The idea of having this hierarchy defined with generics is to allow for different implementations of the same concepts (an IStateSpace will be implemented both as a matrix as an graph, etc). Would can I get away with this? How do you generally solve this kind of problems? Which kind of designs are used in these cases? Thanks

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• Connect two client sockets

  - by Hernán Eche

  Good morning, let's say Java has two kind of sockets... server sockets "ServerSocket" client sockets or just "Socket" ////so Simple ! Imagine the situation of two processes: X Client <-- Y Server The server process Y : has a "ServerSocket", that is listening to a TCP port The client process X : send a connection request through a -client type- "Socket" X ////so Simple ! then the accept() method (in server Y) returns a new client type "Socket", when it occurs, great the two Sockets get "interconected", so the -client socket- in client process, is connected with the -client socket- in the server process then (reading/writing in socket X is like reading/writing in socket Y, and viceversa. ) TWO CLIENT SOCKETS GET INTERCONECTED!! ////so Simple ! BUT... (there is always a But..) What if I create the two CLIENT sockets in same process, and I want to get them "interconected" ? ////mmm Complex =(... even posible? Let's say how to have TWO CLIENT SOCKETS GET INTERCONECTED WITHOUT using an intermediate ServerSocket ? I 've solved it.. by creating two threads for continuously reading A and writing B, and other for reading B and writng A... but I think could be a better way..(or should!) (Those world-energy-consuming threads are not necessary with the client-server aproach) Any help or advice would be appreciated!! Thanks

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