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  • ChaiScript troubles

    - by Ockonal
    Hello guys, I'm using script language ChaiScript with c++ and Qt. I've defined such function: void ChaiPainter::drawRectangle(QPainter *painter, int x, int y, int height, int width) { painter.drawRect(x, y, width, height); } And in application paint-event: void MainWindow::paintEvent(QPaintEvent *event) { QPainter painter(this); chaiPainter->mChai.add(chaiscript::var(&painter), "painter"); chaiPainter->mChai.add(chaiscript::fun(&ChaiPainter::drawRectangle), "drawRect"); chaiPainter->mChai("drawRect(painter, 5, 5, 100, 100)"); } The error is: 'chaiscript::Eval_Error' what(): Error: "No matching function to dispatch to with function 'drawRect'" during evaluation at (1, 1) What I do wrong?

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  • Is it possible to do AJAX calls in a liquid template?

    - by Brian Armstrong
    I'm looking at the liquid templating language for Rails apps: http://wiki.github.com/tobi/liquid/ I'd like my users to also be able to make AJAX calls (just like the ones in rails for periodically_call_remote, observe_field, etc). Is this possible? Assuming the rails helpers can be added as filters, how will the user be able to modify what gets returned by the AJAX call? They cannot modify an rjs file on the server or anything like that. I suppose the AJAX call could return JSON (instead of rendered html) and then the javascript could use that to render something. But I'm having a little trouble envisioning how it would work exactly. If anyone can point me to an example of this or clarify it'd be much appreciated. Thanks!

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  • Hosting a complex online service

    - by jonathanconway
    I have an idea for a web-based service. The implementation is very complex. There will be very few users, and the traffice will be fairly low, but the server-side code could require a lot of resources. Ideally I'd need to have as much control over the servers as possible. How should I arrange hosting for this, when it comes time to release it to the public? Should I do the hosting myself, from my own servers? Trouble is, since I'm not quite an expert on .NET hosting, it might take time to learn and I might make big mistakes. The trouble with using a hosting company is, they might steal my idea, or else, it might cost a lot. Since I'm an un-funded startup I don't have a lot of money to throw at this.

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  • breakthrough programming .net era

    - by Andrew Florko
    I wonder what are .net technologies / c# language improvements you consider as breakthrough in .net era for the last 5-10 years. I mean technologies that shifted developers mind. For example direct-x made assembler nearly abandoned for game programming in the end of XX century and JQuery extremely simplified ajax web development as well as javascript code reusability. What kind of breakthrough .net technologies you expect in the future and what modern .net technologies are just a light evolution of well known approaches. Do you consider .net 4.0 parallel extensions and other improvements as breakthrough, or may be we have reached the point when nothing radical is expected in modern programming?

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  • ASP User Control Issue

    - by Steven
    I am attempting to construct my own date picker using code from several sources. Why won't the calendar hide when visible? myDate.ascx <%@ Control Language="vb" AutoEventWireup="false" CodeBehind="myDate.ascx.vb" Inherits="Website.myDate" %> <asp:TextBox ID="dateText" runat="server" > </asp:TextBox> <asp:Button ID="dateBtn" runat="server" UseSubmitBehavior="false" Text="x" /> <asp:Calendar ID="dateCal" runat="server" ></asp:Calendar> myDate.ascx.vb Partial Public Class myDate Inherits System.Web.UI.UserControl Protected Sub dateCal_SelectionChanged(ByVal sender As Object, ByVal e As EventArgs) Handles dateCal.SelectionChanged dateText.Text = dateCal.SelectedDate ' Update text box' dateCal.Visible = False ' Hide calendar' End Sub Protected Sub dateCal_VisibleMonthChanged(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MonthChangedEventArgs) Handles dateCal.VisibleMonthChanged dateCal.Visible = True ' For some reason, changing the month hides the calendar (so show it)' End Sub Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load dateCal.Visible = False ' Hide calendar on load' End Sub Protected Sub dateBtn_Click(ByVal sender As Object, ByVal e As EventArgs) Handles dateBtn.Click dateCal.Visible = Not dateCal.Visible ' On button press, toggle visibility' End Sub End Class

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  • Calling C function from DTrace scripts

    - by dmeister
    DTrace is impressive, powerful tracing system originally from Solaris, but it is ported to FreeBSD and Mac OSX. DTrace uses a high-level language called D not unlike AWK or C. Here is an example: io:::start /pid == $1/ { printf("file %s offset %d size %d block %llu\n", args[2]->fi_pathname, args[2]->fi_offset, args[0]->b_bcount, args[0]->b_blkno); } Using the command line sudo dtrace -q -s <name>.d <pid> all IOs originated from that process are logged. My question is if and how it is possible to call custom C functions from a DTrace script to do advanced operations with that tracing data during the tracing itself.

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  • IAuthenticationRequest.RedirectToProvider is not supposed to return, yet it does

    - by ripper234
    The method DotNetOpenAuth.OpenId.RelyingParty.IAuthenticationRequest.RedirectToProvider() is documented never to return: Redirects the user agent to the provider for authentication. Execution of the current page terminates after this call. However, it does return under the latest implementation (3.4.3). I'm using the following code: using (var relayingParty = new OpenIdRelyingParty()) { var response = relayingParty.GetResponse(); if (response == null) { // Stage 2: user submitting Identifier var openId = Request.Form["openId"]; relayingParty.CreateRequest(openId).RedirectToProvider(); throw new Exception("Never gets here"); } ... } (The line with "Never gets here" is reached). I need to return an ActionResult from this method ... Is this a known bug? Is there a aorkaround? Should I return EmptyResult? As far as I understand this is a bug - I submitted it in the project issue tracker.

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  • Parsing Indentation-based syntaxes in Haskell's Parsec

    - by pavpanchekha
    I'm trying to parse an indentation-based language (think Python, Haskell itself, Boo, YAML) in Haskell using Parsec. I've seen the IndentParser library, and it looks like it's the perfect match, but what I can't figure out is how to make my TokenParser into an indentation parser. Here's the code I have so far: import qualified Text.ParserCombinators.Parsec.Token as T import qualified Text.ParserCombinators.Parsec.IndentParser.Token as IT lexer = T.makeTokenParser mylangDef ident = IT.identifier lexer This throws the error: parser2.hs:29:28: Couldn't match expected type `IT.TokenParser st' against inferred type `T.GenTokenParser s u m' In the first argument of `IT.identifier', namely `lexer' In the expression: IT.identifier lexer In the definition of `ident': ident = IT.identifier lexer What am I doing wrong? How should I create an IT.TokenParser? Or is IndentParser broken and to be avoided?

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  • Hash 32bit int to 16bit int?

    - by dkamins
    What are some simple ways to hash a 32-bit integer (e.g. IP address, e.g. Unix time_t, etc.) down to a 16-bit integer? E.g. hash_32b_to_16b(0x12345678) might return 0xABCD. Let's start with this as a horrible but functional example solution: function hash_32b_to_16b(val32b) { return val32b % 0xffff; } Question is specifically about JavaScript, but feel free to add any language-neutral solutions, preferably without using library functions. Simple = good. Wacky+obfuscated = amusing.

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  • Expression Tree

    - by nettguy
    My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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  • How can I store data in a table as a trie? (SQL Server)

    - by Matt
    Hi, To make things easier, the table contains all the words in the English dictionary. What I would like to do is be able to store the data as a trie. This way I can traverse the different branches of the trie and return the most relevant result. First, how do I store the data in the table as a trie? Second, how do I traverse the tree? If it helps at all, the suggestion in this previous question is where this question was sparked from. Please make sure it's SQL we're talking about. I understood the Mike Dunlavey's C implementation because of pointers but can't see how this part (The trie itself) works in SQL. Thanks, Matt

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  • Detecting Infinite recursion in Python or dynamic languages

    - by drozzy
    Recently I tried compiling program something like this with GCC: int f(int i){ if(i<0){ return 0;} return f(i-1); and it ran just fine. When I inspected the stack frames the compiler optimized the program to use only one frame, by just jumping back to the beginning of the function and only replacing the arguments to f. And - the compiler wasn't even running in optimized mode. Now, when I try the same thing in Python - I hit maximum recursion wall (or stack overflow). Is there way that a dynamic language like python can take advantage of these nice optimizations? Maybe it's possible to use a compiler instead of an interpreter to make this work? Just curious!

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  • java equivalent of ruby's ||= syntax

    - by brad
    I'm brand new to java, coming from a ruby world. One thing I love about ruby is the very terse syntax such as ||=. I realize of course that a compiled language is different, but I'm wondering if Java has anything similar. In particular, what I do all the time in ruby is something like: someVar ||= SomeClass.new I think this is incredibly terse, yet powerful, but thus far the only method I can think of to achieve the same thing is a very verbose: if(someVar == null){ someVar = new SomeClass() } Just trying to improve my Java-fu and syntax is certainly one area that I'm no pro.

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  • Memory-Mapped Files & Transparent Persistence of Java Objects

    - by geeko
    Greeting All, I want to achieve transparent persistence of Java objects through memory-mapped files (utilize the OS paging/swapping mechanism). My problem is: how can I move a Java object to my memory-mapped block ? Plus, how can I force a new object instance to reside in such blocks ? As you all know, a memory-mapped block can be seen as a byte array, and what I am really asking here is how to overlap the address space of Java objects with the one of such arrays ? If Java does not allow me for this, what cross-platform & garbage-collecting OO language would you advise me to use ? Thank you all in advance.

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  • Are rails timers reliable when using Net::HTTP?

    - by Frank
    Hi All. When reading data from a potentially slow website, I want to ensure that get_response can not hang, and so added a timer to timeout after x seconds. So far, so good. I then read http://ph7spot.com/musings/system-timer which illustrates that in certain situations timer.rb doesn't work due to ruby's implementation of threads. Does anyone know if this is one of these situations? url = URI.parse(someurl) begin Timeout::timeout(30) do response = Net::HTTP.get_response(url) @responseValue = CGI.unescape(response.body) end rescue Exception = e dosomething end

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  • Best practice for copying private instance vars with NSCopying

    - by Ben
    I might be missing something obvious here, but I'm implementing NSCopying on one of my objects. That object has private instance variables that are not exposed via getters, as they shouldn't be used outside the object. In my implementation of copyWithZone:, I need alloc/init the new instance, but also set up its state to match the current instance. I can obviously access current private state from inside copyWithZone:, but I can't set it into the new object, because there are no accessors for that state. Is there a standard way around this while still keeping data privacy intact? Thanks.

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  • Concatenation Operator - PHP

    - by Chaitanya
    This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: a. by not using the concatenation operator, does it effect the performance? b. If it doesn't why at all have the concatenation operator. c. Why have 2 modes of implementation when one does the work?

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  • Comparing images using SIFT

    - by Luís Fernando
    I'm trying to compare 2 images that are taken from a digital camera. Since there may be movement on the camera, I want to first make the pictures "match" and then compare (using some distant function). To match them, I'm thinking about cropping the second picture and using SIFT to find it inside the first picture... it will probably have a small difference on scale/translation/rotation so then I'd need to find the transformation matrix that converts image 1 to image 2 (based on points found by SIFT) any ideas on how to do that (or I guess that's a common problem that may have some opensource implementation?)? thanks

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  • Writing a Compiler for .net - IL or Bytecode?

    - by Michael Stum
    I'm currently diving into the inner workings of .net, which means IL. As an exercise, I want to build a brainf..k compiler for .net (yes, they already exist, but as said it's for learning purposes). For the moment I'm just writing some text files that contain .il and compile them with ilasm, which works. But I wonder if I could/should go one level deeper and write bytecode directly? My "concern" is the Windows PE Stuff when compiling an EXE - instead of ilasm I would need some sort of Bytecode linker that would take my MSIL/CIL bytecode and generate the PE Stuff for it? Or do compilers "only" compile their language to IL and execute ilasm? Is there a managed version of it that I can call/embed from my compiler?

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  • Thread safe lockfree mutual ByteArray queue

    - by user313421
    A byte stream should be transferred and there is one producer thread and a consumer one. Speed of producer is higher than consumer most of the time, and I need enough buffered data for QoS of my application. I read about my problem and there are solutions like shared buffer, PipeStream .NET class ... This class is going to be instantiated many times on server so I need and optimized solution. Is it good idea to use a Queue of ByteArray ? If yes, I'll use an optimization algorithm to guess the Queue size and each ByteArray capacity and theoretically it fits my case. If no, I what's the best approach ? Please let me know if there's a good lock free thread safe implementation of ByteArray Queue in C# or VB. Thanks in advance

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  • Dynamic choices for Django SelectMultiple Widget

    - by PhilGo20
    I'm building a form (not modelForm) where i'd like to use the SelectMultiple Widget to display choices based on a query done during the init of the form. I can think of a few way to do this but I am not exactly clear on the right way to do it. I see different options. I get the "choices" I should pass to the widget in the form init but I am not sure how I should pass them. class NavigatorExportForm(forms.Form): def __init__(self,user, app_id, *args,**kwargs): super (NavigatorExportForm,self ).__init__(*args,**kwargs) # populates the form language_choices = Navigator.admin_objects.get(id=app_id).languages.all().values_list('language', flat=True) languages = forms.CharField(max_length=2, widget=forms.SelectMultiple(choices=???language_choices))

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  • What are logical and path queries

    - by NomeN
    I'm reading a paper which mentions that a language for refactoring has three specific requirements. functional features (like ML) logical queries (like Datalog) path queries (like Datalog) I know what they mean by functional features, but I'm not totally clear on the latter two and can't find a clear explanation either. Although I have a good idea after what I could find on the subjects, I need to be sure so here goes: Could the SO-community please clearly explain to me what logical queries and path queries are? Or at the very least what the people from the paper meant?

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  • What Python based Dashboard options exist?

    - by stuartcw
    I want to create a Dashboard on each server to show it's health and the results of some daily processing. I plan to hook up shell scripts and Python programs to collect the data. Instead of writing a web-based interface, I thought it would be good to use a python based web dashboard that could render the results in various business user and manager friendly formats. What are my options to do this? I am primarily interested in Python RedHat Linux, but other platforms are interesting too. I'm also open to Perl and Ruby based solutions especially if the plugins can be language neutral.

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  • Connection string in app.config in a class library

    - by Copeleto
    I am creating solution and inside I have three projects: A WCF Service Library Project A DataAccess Project (Class Library) A Web site for hosting WCF service The implementation of the service is on the project # 1, but in order to access the DataBase I use a second project that implements the data access using a class library project. That problem is in order to get data access I need to configure a connection string, but that connection string must be configurable in a production environment, I meant in production I am going to deploy the site, which is a very simple project that contains only a reference WCF Service Library Project then a guy from database department will configure the connection string. In development I have an app.config on the data access project but when I do the release that app.config is embedded on the dll. Any ideas how can we achieve our purpose

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  • Coordinate geometry operations in images/discrete space

    - by avd
    I have images which have line segments, rays etc. I am representing these line segments using Bresenham algorithm (means whatever coordinates I get using this algorithm between two points). Now I want to do operations such as finding intersection point between two line segments, finding the projection of one vector onto other etc... The problem is I am not working in continuous space. The line segments are being approximated using Bresenham algorithm. So I want suggestions on what are the best and most efficient ways to do this? A link to C++ library or implementation would also be good enough. Please suggest some books which deal with such problems.

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