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  • Get an Arduino and Android phone to communicate over the web

    - by Saleem
    I am writing an Android application to communicate with my Arduino over the web. The Arduino is running a web server through an Ethernet shield. I am attaching my code, but I will explain it here so you will understand what I am trying to do. The Android sends an HTTP request in the format http://192.168.1.148/?Lights=1. The Arduino gets the request, executes the command (in this case turning on some lights) and then responds to the Android device by simply sending the string "Lights=On". The Android will then change the color of the button to notify the user that the command was executed successfully. The Arduino is getting the instruction and executing it and sending the response but my button color is not changing. I know that the Android device is getting the string because I added a debug line to change the text on the button to the received response. The relevant code for the Android device is: ((Button) v).setText(sb.toString()); //This works and the button text changes to "Lights=On". //Test response and update button if(sb.toString()=="Lights=On"){ v.getBackground().setColorFilter(0xFFFFFF00, PorterDuff.Mode.MULTIPLY); Drawable d = lightOff.getBackground(); lightOff.invalidateDrawable(d); d.clearColorFilter(); } The Arduino code is: if(s=="Lights"){ switch(client.read()){ case '0': digitalWrite(LightPin,0); client.print("Lights=Off"); //debug Serial.println("Lights=Off"); break; case '1': digitalWrite(LightPin,1); client.print("Lights=On"); Serial.println("Lights=On"); break; } } Please let me know if you need more of the code to answer this question.

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  • CssClass and default images in ServerContol

    - by Jeff Dege
    I'm writing a ServerControl in ASP.NET 3.5, and I'm exposing CssClass, so the user can manipulate the visual appearance of the control. My problem is that I want to establish reasonable defaults, so that the user doesn't have to configure CSS unless he wants to change the defaults. My specific problem is that my control is emitting html divs, that need to display background images. I want the user to be able to specify a different image in CSS, but I want to display a default background image, and I can't make that work. The entire server control is emitted as a div, with a class name set to the value the user provided in CssClass. The div that needs the background image is enclosed within this outer div, with a class name of its own. I am currently setting the background image in CSS on the page that contains the control: <style type="text/css"> .cssClass .innerDiv { background-image: url("http://...."); } </style> With this the proper image is drawn. But if it's not there, no image is drawn. What I want is for the ServerControl to emit some CSS that will define these image urls, that would be over-ridden by any css that was added by the user, and for that default CSS to include URLs to images embedded in the ServerControl's assembly. And I'm not sure of how to do either. Nor, for that matter, am I sure this is the best approach. Any ideas?

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  • MS Access: Why is ADODB.Recordset.BatchUpdate so much slower than Application.ImportXML?

    - by apenwarr
    I'm trying to run the code below to insert a whole lot of records (from a file with a weird file format) into my Access 2003 database from VBA. After many, many experiments, this code is the fastest I've been able to come up with: it does 10000 records in about 15 seconds on my machine. At least 14.5 of those seconds (ie. almost all the time) is in the single call to UpdateBatch. I've read elsewhere that the JET engine doesn't support UpdateBatch. So maybe there's a better way to do it. Now, I would just think the JET engine is plain slow, but that can't be it. After generating the 'testy' table with the code below, I right clicked it, picked Export, and saved it as XML. Then I right clicked, picked Import, and reloaded the XML. Total time to import the XML file? Less than one second, ie. at least 15x faster. Surely there's an efficient way to insert data into Access that doesn't require writing a temp file? Sub TestBatchUpdate() CurrentDb.Execute "create table testy (x int, y int)" Dim rs As New ADODB.Recordset rs.CursorLocation = adUseServer rs.Open "testy", CurrentProject.AccessConnection, _ adOpenStatic, adLockBatchOptimistic, adCmdTableDirect Dim n, v n = Array(0, 1) v = Array(50, 55) Debug.Print "starting loop", Time For i = 1 To 10000 rs.AddNew n, v Next i Debug.Print "done loop", Time rs.UpdateBatch Debug.Print "done update", Time CurrentDb.Execute "drop table testy" End Sub I would be willing to resort to C/C++ if there's some API that would let me do fast inserts that way. But I can't seem to find it. It can't be that Application.ImportXML is using undocumented APIs, can it?

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  • How to architect Rails site that can be edited while running?

    - by Chris Kimpton
    Hi, I am writing a Rails app that "scrapes/navigates" some other websites and webservices for content. I am using Mechanize and Savon to do the heavylifting. But given the dynamic nature of the web, I'd like to make my calls to these editable by the admin users of the site - rather than requiring me to release a new version of the site. The actual scraping thread happens async to the website, using the daemons gem. My requirements are: Thinking that the scraping/webservice calling code is quite simple, the easiest route is to make the whole class editable by the admins. Keep a history of the scraping code - so that we can fairly easily revert if we introduce a problem. Initially use the code from the file system, but as soon as thats been edited and stored somewhere, to use that code instead. I am thinking my options are: Store the code in the db (with a history table for the old versions) Store the code in a private git repo somewhere and access that for the history/latest versions. I am thinking the git route might be easiest, given its raison d'etre is to track file history... But perhaps there is a gem/plugin that does all this for me, out of the box? Thanks in advance for any tips/advice. ~chris

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  • Uncompress OpenOffice files for better storage in version control

    - by Craig McQueen
    I've heard discussion about how OpenOffice (ODF) files are compressed zip files of XML and other data. So making a tiny change to the file can potentially totally change the data, so delta compression doesn't work well in version control systems. I've done basic testing on an OpenOffice file, unzipping it and then rezipping it with zero compression. I used the Linux zip utility for my testing. OpenOffice will still happily open it. So I'm wondering if it's worth developing a small utility to run on ODF files each time just before I commit to version control. Any thoughts on this idea? Possible better alternatives? Secondly, what would be a good and robust way to implement this little utility? Bash shell that calls zip (probably Linux only)? Python? Any gotchas you can think of? Obviously I don't want to accidentally mangle a file, and there are several ways that could happen. Possible gotchas I can think of: Insufficient disk space Some other permissions issue that prevents writing the file or temporary files ODF document is encrypted (probably should just leave these alone; the encryption probably also causes large file changes and thus prevents efficient delta compression)

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  • Where do you take mocking - immediate dependencies, or do you grow the boundaries...?

    - by Peter Mounce
    So, I'm reasonably new to both unit testing and mocking in C# and .NET; I'm using xUnit.net and Rhino Mocks respectively. I'm a convert, and I'm focussing on writing behaviour specifications, I guess, instead of being purely TDD. Bah, semantics; I want an automated safety net to work above, essentially. A thought struck me though. I get programming against interfaces, and the benefits as far as breaking apart dependencies goes there. Sold. However, in my behaviour verification suite (aka unit tests ;-) ), I'm asserting behaviour one interface at a time. As in, one implementation of an interface at a time, with all of its dependencies mocked out and expectations set up. The approach seems to be that if we verify that a class behaves as it should against its collaborating dependencies, and in turn relies on each of those collaborating dependencies to have signed that same quality contract, we're golden. Seems reasonable enough. Back to the thought, though. Is there any value in semi-integration tests, where a test-fixture is asserting against a unit of concrete implementations that are wired together, and we're testing its internal behaviour against mocked dependencies? I just re-read that and I think I could probably have worded it better. Obviously, there's going to be a certain amount of "well, if it adds value for you, keep doing it", I suppose - but has anyone else thought about doing that, and reaped benefits from it outweighing the costs?

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  • WCF Service instead of ASMX Web Service?

    - by wchrisjohnson
    I'm writing a SOAP Server that will act as an endpoint for an external client. The external client expects SOAP 1.1. I'll be taking embedded business objects in the SOAP messages and passing them to an internal application, getting responses back and responding with SOAP messages to the eternal client. I did the traditional ASMX based web services several years ago. Now, I've been exploring WCF Services and wondering the best approach to take. 1) Should WCF be considered a superset of ASMX web services? 2) Is there any reason to still write new web services using ASMX instead of WCF? 3) Does WCF provide better facilities for working with SOAP messages, as opposed to SOAP Extensions? 4) Can I restrict communication to SOAP 1.1 using WCF, the way I can with a web.config change in ASMX? 5) Does WCF have an easy way to log or review the requests that hit the service without resorting to something like SOAP extensions? Sorry my questions are not very specific; still trying to get handle on what I need to know... Using VS2008, Windows Server 2008. Chris

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  • PHPUnit and autoloaders: Determining whether code is running in test-scope?

    - by pinkgothic
    Premise I know that writing code to act differently when a test is run is hilariously bad practise, but I may've actually come across a scenario in which it may be necessary. Specifically, I'm trying to test a very specific wrapper for HTML Purifier in the Zend framework - a View Helper, to be exact. The HTML Purifier autoloader is necessary because it uses a different logic to the autoloaders we otherwise have. Problem require()-ing the autoloader at the top of my View Helper class, gives me the following in test-scope: HTML Purifier autoloader registrar is not compatible with non-static object methods due to PHP Bug #44144; Please do not use HTMLPurifier.autoload.php (or any file that includes this file); instead, place the code: spl_autoload_register(array('HTMLPurifier_Bootstrap', 'autoload')) after your own autoloaders. Replacing the require() with spl_autoload_register(array('HTMLPurifier_Bootstrap', 'autoload')) as advertised means the test runs fine, but the View Helper dies a terrible death claiming: Zend_Log[3707]: ErrorController caught LogicException "Passed array does not specify an existing static method (class 'HTMLPurifier_Bootstrap' not found)" (Our test folder structure is slightly different to our Zend folder structure by necessity.) Question(s) After tinkering with it, I'm thinking I'll need to pick an autoloader-loading depending on whether things are in the test scope or not. Do I have another option to include HTMLPurifier's autoloading routine in both cases that I'm not seeing due to tunnel vision? If not, do I have to find a means to differentiate between test-environment and production-environment this with my own code (e.g. APPLICATION_ENV) - or does PHPUnit support this godawful hackery of mine natively by setting a constant that I could check whether its been defined(), or similar shenanigans? (My Google-fu here is weak! I'm probably just doing it wrong.)

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  • Programatic re-evalutation of MVVM command's "can execute" state

    - by dzs
    Hello! I'm writing a WPF application using the MVVM pattern, based on the following article: WPF Apps With The Model-View-ViewModel Design Pattern I have two buttons on my View with the buttons' "Command" property bound (with data binding) to a given instance of the RelayCommand class (see "Figure 3 The RelayCommand Class" from the article above). The RelayCommand class has support for checking whether the given command can be executed. WPF automatically disables buttons whose command cannot be executed. Each of my commands (in the ViewModel class) start a background operation, and the command cannot be executed again until the background operation is finished. The RelayCommand instances have information whether the background operation is still working or it is finished. My problem is the following: after pressing the any of the buttons, the buttons automaticaly go disabled (which is OK) because the background operation started and the command cannot be executed until it is finished, but after the operation had finished, the buttons don't go enabled automatically because their command's "can be executed" predicate is not automatically reevaluated. The reevaluation can be manually triggered by having the application loose and regain focus (by pressing ALT+TAB). After doing this trick, the buttons get enabled once again. How can I programatically reevaluate the buttons' command's "can execute" state?

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  • Use of const double for intermediate results

    - by Arne
    Hi, I a writing a Simulation program and wondering if the use of const double is of any use when storing intermediate results. Consider this snippet: double DoSomeCalculation(const AcModel &model) { (...) const double V = model.GetVelocity(); const double m = model.GetMass(); const double cos_gamma = cos(model.GetFlightPathAngleRad()); (...) return m*V*cos_gamma*Chi_dot; } Note that the sample is there only to illustrate -- it might not make to much sense from the engineering side of things. The motivation of storing for example cos_gamma in a variable is that this cosine is used many time in other expressions covered by (...) and I feel that the code gets more readable when using cos_gamma rather than cos(model.GetFlightPathAngleRad()) in various expressions. Now the actual is question is this: since I expect the cosine to be the same througout the code section and I actually created the thing only as a placeholder and for convenience I tend to declare it const. Is there a etablished opinion on wether this is good or bad practive or whether it might bite me in the end? Does a compiler make any use of this additional information or am I actually hindering the compiler from performing useful optimizations? Arne

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  • Are there any ASP.NET MVC subscription-based starter kits or examples?

    - by Wayne M
    Basically something that handles the low-level "plumbing" code for a subscription-based service. I see a lot of things dealing with basic membership, but nothing that handles the subscription aspect (recurring billing, automated jobs for setting up billing, notification for billing, etc). This might be the one thing that keeps me from using ASP.NET MVC for my SaaS idea, since it would take a fair amount of development time to write my own; if I go with my other option, Ruby on Rails, I can buy a kit that does all of this for $250. I haven't found anything even remotely close to this for .NET - all of the SaaS sample apps I've seen are more like StackOverflow et all where you have one site that multiple people log on to, not the web application model where you have subscribers who are billed monthly, each of whom has users and other entities (e.g. Customers, Tasks, etc) for their own site. Is there anything similar for ASP.NET, or some kind of guidelines for writing my own if I have to, so I don't waste too much time? As a startup that means that I'm doing all the coding myself. I've found this, but it seems to only be for billing and didn't seem to have much (any?) documentation on exactly how to set it up.

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  • What does it mean that "Lisp can be written in itself?"

    - by Mason Wheeler
    Paul Graham wrote that "The unusual thing about Lisp-- in fact, the defining quality of Lisp-- is that it can be written in itself." But that doesn't seem the least bit unusual or definitive to me. ISTM that a programming language is defined by two things: Its compiler or interpreter, which defines the syntax and the semantics for the language by fiat, and its standard library, which defines to a large degree the idioms and techniques that skilled users will use when writing code in the language. With a few specific exceptions, (the non-C# members of the .NET family, for example,) most languages' standard libraries are written in that language for two very good reasons: because it will share the same set of syntactical definitions, function calling conventions, and the general "look and feel" of the language, and because the people who are likely to write a standard library for a programming language are its users, and particularly its designer(s). So there's nothing unique there; that's pretty standard. And again, there's nothing unique or unusual about a language's compiler being written in itself. C compilers are written in C. Pascal compilers are written in Pascal. Mono's C# compiler is written in C#. Heck, even some scripting languages have implementations "written in itself". So what does it mean that Lisp is unusual in being written in itself?

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  • Idiomatic STL: Iterating over a list and inserting elements

    - by mkilling
    I'm writing an algorithm that iterates over a list of points, calculates the distance between them and inserts additional points if the distance is too great. However I seem to be lacking the proper familiarity with STL to come up with an elegant solution. I'm hoping that I can learn something, so I'll just show you my code. You might have some hints for me. for (std::list<PathPoint>::iterator it = ++points_.begin(); it != points_.end(); it++) { Vector curPos = it->getPosition(); Vector prevPos = (--it)->getPosition(); Vector vecFromPrev = curPos - prevPos; float distance = vecFromPrev.abs(); it++; if (distance > MAX_DISTANCE_BETWEEN_POINTS) { int pointsToInsert = (int)(distance / MAX_DISTANCE_BETWEEN_POINTS); Vector curPos = prevPos; for (int i = 0; i < pointsToInsert; i++) { curPos += vecFromPrev / pointsToInsert; it = points_.insert(it, PathPoint(curPos, false)); it++; } } }

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  • Using a version control system as a data backend

    - by JacobM
    I'm involved in a project that, among other things, involves storing edits and changes to a large hierarchical document (HTML-formatted text). We want to include versioning of textual changes and of structural changes. Currently we're maintaining the tree of document sections in a relational database, but as we start working on how to manage versioning of structural changes, it's clear that we're in danger of having to write a lot of the functionality that a version control system provides. We don't want to reinvent the wheel. Is it possible that we could use an existing version control system as the data store, at least for the document itself? Presumably we could do so by writing out new versions to the filesystem, and keeping that directory under version control (and programmatically doing commits and so forth) but it would be better if we could directly interact with the repository via code. The VCS that we are most familiar with is Subversion, but I'm not thrilled with how Subversion represents changes to the directory structure -- it would be nice if we could see that a particular revision included moving a section from Chapter 2 to Chapter 6, rather than just seeing a new version of the tree. This sounds more like the way a system like Mercurial handles changes to the structure. Any advice? Do VCS's have public APIs and so forth? The project is in Java (with Spring) if it matters.

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  • Simple in-place discrete fourier transform ( DFT )

    - by Adam
    I'm writing a very simple in-place DFT. I am using the formula shown here: http://en.wikipedia.org/wiki/Discrete_Fourier_transform#Definition along with Euler's formula to avoid having to use a complex number class just for this. So far I have this: private void fft(double[] data) { double[] real = new double[256]; double[] imag = new double[256]; double pi_div_128 = -1 * Math.PI / 128; for (int k = 0; k < 256; k++) { for (int n = 0; n < 256; n++) { real[k] += data[k] * Math.Cos(pi_div_128 * k * n); imag[k] += data[k] * Math.Sin(pi_div_128 * k * n); } data[k] = Math.Sqrt(real[k] * real[k] + imag[k] * imag[k]); } } But the Math.Cos and Math.Sin terms eventually go both positive and negative, so as I'm adding those terms multiplied with data[k], they cancel out and I just get some obscenely small value. I see how it is happening, but I can't make sense of how my code is perhaps mis-representing the mathematics. Any help is appreciated. FYI, I do have to write my own, I realize I can get off-the shelf FFT's.

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  • C++ Serialization Clean XML Similar to XSTREAM

    - by disown
    I need to write a linux c++ app which saves it settings in XML format (for easy hand editing) and also communicates with existing apps through XML messages over sockets and HTTP. Problem is that I haven't been able to find any intelligent libs to help me, I don't particular feel like writing DOM or SAX code just to write and read some very simple messages. Boost Serialization was almost a match, but it adds a lot of boost-specific data to the xml it generates. This obviously doesn't work well for interchange formats. I'm wondering if it is possible to make Boost Serialization or some other c++ serialization library generate clean xml. I don't mind if there are some required extra attributes - like a version attribute, but I'd really like to be able to control their naming and also get rid of 'features' that I don't use - tracking_level and class_id for instance. Ideally I would just like to have something similar to xstream in Java. I am aware of the fact that c++ lacks introspection and that it is therefore necessary to do some manual coding - but it would be nice if there was a clean solution to just read and write simple XML without kludges! If this cannot be done I am also interested in tools where the XML schema is the canonical resource (contract first) - a good JAXB alternative to C++. So far I have only found commercial solutions like CodeSynthesis XSD. I would prefer open source solutions. I have tried gSoap - but it generates really ugly code and it is also SOAP-specific. In desperation I also started looking at alternative serialization formats for protobuffers. This exists - but only for Java! It really surprises me that protocol buffers seems to be a better supported data interchange format than XML. I'm going mad just finding libs for this app and I really need some new ideas. Anyone?

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  • My First F# program

    - by sudaly
    Hi I just finish writing my first F# program. Functionality wise the code works the way I wanted, but not sure if the code is efficient. I would much appreciate if someone could review the code for me and point out the areas where the code can be improved. Thanks Sudaly open System open System.IO open System.IO.Pipes open System.Text open System.Collections.Generic open System.Runtime.Serialization [<DataContract>] type Quote = { [<field: DataMember(Name="securityIdentifier") >] RicCode:string [<field: DataMember(Name="madeOn") >] MadeOn:DateTime [<field: DataMember(Name="closePrice") >] Price:float } let m_cache = new Dictionary<string, Quote>() let ParseQuoteString (quoteString:string) = let data = Encoding.Unicode.GetBytes(quoteString) let stream = new MemoryStream() stream.Write(data, 0, data.Length); stream.Position <- 0L let ser = Json.DataContractJsonSerializer(typeof<Quote array>) let results:Quote array = ser.ReadObject(stream) :?> Quote array results let RefreshCache quoteList = m_cache.Clear() quoteList |> Array.iter(fun result->m_cache.Add(result.RicCode, result)) let EstablishConnection() = let pipeServer = new NamedPipeServerStream("testpipe", PipeDirection.InOut, 4) let mutable sr = null printfn "[F#] NamedPipeServerStream thread created, Wait for a client to connect" pipeServer.WaitForConnection() printfn "[F#] Client connected." try // Stream for the request. sr <- new StreamReader(pipeServer) with | _ as e -> printfn "[F#]ERROR: %s" e.Message sr while true do let sr = EstablishConnection() // Read request from the stream. printfn "[F#] Ready to Receive data" sr.ReadLine() |> ParseQuoteString |> RefreshCache printfn "[F#]Quot Size, %d" m_cache.Count let quot = m_cache.["MSFT.OQ"] printfn "[F#]RIC: %s" quot.RicCode printfn "[F#]MadeOn: %s" (String.Format("{0:T}",quot.MadeOn)) printfn "[F#]Price: %f" quot.Price

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  • File-level filesystem change notification in Mac OS X

    - by Paul J. Lucas
    I want my code to be notified when any file under (either directly or indirectly) a given directory is modified. By "modified", I mead I want my code to be notified whenever a file's contents are altered, it's renamed, or it's deleted; or if a new file is added. For my application, there can be thousands of files. I looked as FSEvents, but its Technology Overview says, in part: The important point to take away is that the granularity of notifications is at a directory level. It tells you only that something in the directory has changed, but does not tell you what changed. It also says: The file system events API is also not designed for finding out when a particular file changes. For such purposes, the kqueues mechanism is more appropriate. However, in order to use kqueue on a given file, one has to open the file to obtain a file descriptor. It's impractical to manage thousands of file descriptors (and would probably exceed the maximum allowable number of open file descriptors anyway). Curiously, under Windows, I can use the ReadDirectoryChangesW() function and it does precisely what I want. So how can one do what I want under Mac OS X? Or, asked another way: how would one go about writing the equivalent of ReadDirectoryChangesW() for Mac OS X in user-space (and do so very efficiently)?

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  • Obj-C: ++variable is increasing by two instead of one

    - by Eli Garfinkel
    I am writing a program that asks users yes/no questions to help them decide how to vote in an election. I have a variable representing the question number called questionnumber. Each time I go through the switch-break loop, I add 1 to the questionnumber variable so that the next question will be displayed. This works fine for the first two questions. But then it skips the third question and moves on to the fourth. When I have more questions in the list, it skips every other question. Somewhere, for some reasons, the questionnumber variable is increasing when I don't want it to. Please look at the code below and tell me what I'm doing wrong. Thank you! Eli import "MainView.h" import @implementation MainView @synthesize Question; @synthesize mispar; int conservative = 0; int liberal = 0; int questionnumber = 1; (IBAction)agreebutton:(id)sender { ++liberal; } (IBAction)disagreebutton:(id)sender { ++conservative; } (IBAction)nextbutton:(id)sender { ++questionnumber; switch (questionnumber) { case 2: Question.text = @"Congress should pass a law that would ban Americans from earning more than one hundred million dollars in any given year."; break; case 3: Question.text = @"It is not fair to admit people to a university or employ them on the basis of merit alone. Factors such as race, gender, class, and sexual orientation must also be considered."; break; case 4: Question.text = @"There are two Americas - one for the rich and one for the poor."; break; case 5: Question.text = @"Top quality health care should be free for all."; break; default: break; } } @end

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  • DataTable vs. Collection in .Net

    - by B Pete
    I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel. I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts. I'm tempted to use a collection of "Register" objects that I can access via a unique key. It would be a little more coding up front, but seems like a cleaner solution overall. I should still be able to use LINQ to dataset to query subsets of registers when I need them, but would also be able to grab a single field using a the key value, something like this: Registers(keyValue).fieldName). Which would be a cleaner approach to the problem? Is there a way to read/write XML into a Collection without needing custom code? Could this be accomplished using String for a key?

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  • Multithreading and Interrupts

    - by Nicholas Flynt
    I'm doing some work on the input buffers for my kernel, and I had some questions. On Dual Core machines, I know that more than one "process" can be running simultaneously. What I don't know is how the OS and the individual programs work to protect collisions in data. There are two things I'd like to know on this topic: (1) Where do interrupts occur? Are they guaranteed to occur on one core and not the other, and could this be used to make sure that real-time operations on one core were not interrupted by, say, file IO which could be handled on the other core? (I'd logically assume that the interrupts would happen on the 1st core, but is that always true, and how would you tell? Or perhaps does each core have its own settings for interrupts? Wouldn't that lead to a scenario where each core could react simultaneously to the same interrupt, possibly in different ways?) (2) How does the dual core processor handle opcode memory collision? If one core is reading an address in memory at exactly the same time that another core is writing to that same address in memory, what happens? Is an exception thrown, or is a value read? (I'd assume the write would work either way.) If a value is read, is it guaranteed to be either the old or new value at the time of the collision? I understand that programs should ideally be written to avoid these kinds of complications, but the OS certainly can't expect that, and will need to be able to handle such events without choking on itself.

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  • DRY Authenticated Tasks in Cocoa (with distributed objects)

    - by arbales
    I'm kind of surprise/infuriated that the only way for me to run an authenticated task, like perhaps sudo gem install shi*t, is to make a tool with pre-written code. I'm writing a MacRuby application, which doesn't seem to expose the KAuthorization* constants/methods. So.. I learned Cocoa and Objective-C. My application creates a object, serves it and calls the a tool that elevates itself and then performs a selector on a distributed object (in the tool's thread). I hoped that the distributed object's methods would evaluated inside the tool, so I could use delegation to create "privileged" tasks. If this won't work, don't try to save it, I just want a DRY/cocoa solution. AuthHelper.m //AuthorizationExecuteWithPrivileges of this. AuthResponder* my_responder = [AuthResponder sharedResponder]; // Gets the proxy object (and it's delegate) NSString *selector = [NSString stringWithUTF8String:argv[3]]; NSLog(@"Performing selector: %@", selector); setuid(0); if ([[my_responder delegate] respondsToSelector:NSSelectorFromString(selector)]){ [[my_responder delegate] performSelectorOnMainThread:NSSelectorFromString(selector) withObject:nil waitUntilDone:YES]; } RandomController.m - (void)awakeFromNib { helperToolPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingString:@"/AuthHelper"]; delegatePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingString:@"/ABExtensions.rb"]; AuthResponder* my_responder = [AuthResponder initAsService]; [my_responder setDelegate:self]; } -(oneway void)install_gems{ NSArray *args = [NSArray arrayWithObjects: @"gem", @"install", @"sinatra", nil]; [NSTask launchedTaskWithLaunchPath:@"/usr/bin/sudo" arguments:args]; NSLog(@"Ran AuthResponder.delegate.install_gems"); // This prints. } ... other privileges tasks. "sudo gem update --system" for one. I'm guessing the proxy object is performing the selector in it's own thread, but I want the current (privileged thread) to do it so I can use sudo. Can I force the distributed object to evaluate the selector on the tool's thread? How else can I accomplish this dryly/cocoaly?

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  • D callbacks in C functions

    - by Caspin
    I am writing D2 bindings for Lua. This is in one of the Lua header files. typedef int (*lua_CFunction) (lua_State *L); I assume the equivalent D2 statement would be: extern(C) alias int function( lua_State* L ) lua_CFunction; Lua also provides an api function: void lua_pushcfunction( lua_State* L, string name, lua_CFunction func ); If I want to push a D2 function does it have to be extern(C) or can I just use the function? int dfunc( lua_State* L ) { std.stdio.writeln("dfunc"); } extern(C) int cfunc( lua_State* L ) { std.stdio.writeln("cfunc"); } lua_State* L = lua_newstate(); lua_pushcfunction(L, "cfunc", &cfunc); //This will definitely work. lua_pushcfunction(L, "dfunc", &dfunc); //Will this work? If I can only use cfunc, why? I don't need to do anything like that in C++. I can just pass the address of a C++ function to C and everything just works.

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  • How to install DBD::mysql on OS X Server 10.6?

    - by Zoran Simic
    Trying to install DBD::mysql on OS X Server 10.6 (mac mini server). But I'm missing the mysql headers apparently. Since mysql is already part of OS X Server 10.6, I would like to NOT install anything else (no fink or darwin ports installs), just whatever's needed to get DBD::mysql installed and working. Do you know how I could do that? Do I have to install the headers somewhere? And if so, where? (again: I don't want to install another version of mysql on the box, want to use the version it came with). Is there a way to install DBD::mysql without compiling any C files? This is the error I get (the actual error is much longer, but these are the most meaningful bits, this is the first error reported). Checking if your kit is complete... Looks good Unrecognized argument in LIBS ignored: '-pipe' Note (probably harmless): No library found for -lmysqlclient Multiple copies of Driver.xst found in: /Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI/ /System/Library/Perl/Extras/5.10.0/darwin-thread-multi-2level/auto/DBI/ at Makefile.PL line 907 Using DBI 1.611 (for perl 5.010000 on darwin-thread-multi-2level) installed in /Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI/ Writing Makefile for DBD::mysql cp lib/DBD/mysql.pm blib/lib/DBD/mysql.pm cp lib/DBD/mysql/GetInfo.pm blib/lib/DBD/mysql/GetInfo.pm cp lib/DBD/mysql/INSTALL.pod blib/lib/DBD/mysql/INSTALL.pod cp lib/Bundle/DBD/mysql.pm blib/lib/Bundle/DBD/mysql.pm gcc-4.2 -c -I/Library/Perl/5.10.0/darwin-thread-multi-2level/auto/DBI -I/usr/include -fno-omit-frame-pointer -pipe -D_P1003_1B_VISIBLE -DSIGNAL_WITH_VIO_CLOSE -DSIGNALS_DONT_BREAK_READ -DIGNORE_SIGHUP_SIGQUIT -DDBD_MYSQL_INSERT_ID_IS_GOOD -g -arch x86_64 -arch i386 -arch ppc -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -I/usr/local/include -Os -DVERSION=\"4.014\" -DXS_VERSION=\"4.014\" "-I/System/Library/Perl/5.10.0/darwin-thread-multi-2level/CORE" dbdimp.c In file included from dbdimp.c:20: dbdimp.h:22:49: error: mysql.h: No such file or directory dbdimp.h:23:45: error: mysqld_error.h: No such file or directory dbdimp.h:25:49: error: errmsg.h: No such file or directory

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  • if (i == 2) or if (2 == i) ?

    - by Maroloccio
    I usually use if (i == 2) in preference to if (2 == i) On occasion, I would switch things around when writing xUnit-type tests from scratch so as to follow the assertion convention of "expected" preceding "actual". When adding to existing unit tests, I always follow the style I find. No matter what, I always try to keep things consistent. Today I checked out some code with a lot of "if (2 == i)" and started wondering: which style is more "popular" nowadays? is popularity language-dependent? The latter probably because I am aware of why the "if (2 == i)" became common in the first place (C heritage) and because I see some languages go as far as disallowing assignments within conditions (e.g. Python). I thought about downloading some sources: apt-get source linux-source eclipse openoffice.org expanding them and performing a quick grep: grep --color --include=*.java --include=*.c -ERI \ "if[[:space:]]*\([[:space:]]*[[:digit:]]+[[:space:]]==" . or creating a quick "poll": http://goo.gl/mod/ciMF after a bit of searching and asking around, I am still not sure. So I am asking you: which way to go?

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