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  • "Inlining" (kind of) functions at runtime in C

    - by fortran
    Hi, I was thinking about a typical problem that is very JIT-able, but hard to approach with raw C. The scenario is setting up a series of function pointers that are going to be "composed" (as in maths function composition) once at runtime and then called lots and lots of times. Doing it the obvious way involves many virtual calls, that are expensive, and if there are enough nested functions to fill the CPU branch prediction table completely, then the performance with drop considerably. In a language like Lisp, I could probably process the code and substitute the "virtual" call by the actual contents of the functions and then call compile to have an optimized version, but that seems very hacky and error prone to do in C, and using C is a requirement for this problem ;-) So, do you know if there's a standard, portable and safe way to achieve this in C? Cheers

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  • Restrict confirm message on page reload with f5

    - by Max
    In my JSP page I am using post method while submitting the page. So once I go from Page 1 to page 2. In Page 2, If I press F5 I am getting alert as "To display this page, Firefox must send information that will repeat any action (such as a search or order confirmation) that was performed earlier." I knew this question is a bit sarcastic but please give me an Idea. I can't change my method from POST to GET because I need to send large amount of data. Thanks in advance... Edited: In my Page1.JSP I call onClick function in that function I call action as "/page2servlet.do". Now, In Java side I use Spring Framework. With MVC Object I return to page2.jsp. So where do the response.sendRedirect Fit.

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  • KindError: Property r must be an instance of SecondModel, why ?

    - by zjm1126
    class FirstModel(db.Model): p = db.StringProperty() r=db.ReferenceProperty(SecondModel) class SecondModel(db.Model): r = db.ReferenceProperty(FirstModel) class sss(webapp.RequestHandler): def get(self): a=FirstModel() a.p='sss' a.put() b=SecondModel() b.r=a b.put() a.r=b a.put() self.response.out.write(str(b.r.p)) the error is : Traceback (most recent call last): File "D:\Program Files\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 511, in __call__ handler.get(*groups) File "D:\zjm_code\helloworld\a.py", line 158, in get a.r=b File "D:\Program Files\Google\google_appengine\google\appengine\ext\db\__init__.py", line 3009, in __set__ value = self.validate(value) File "D:\Program Files\Google\google_appengine\google\appengine\ext\db\__init__.py", line 3048, in validate (self.name, self.reference_class.kind())) KindError: Property r must be an instance of SecondModel thanks

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  • How to restart Linux from inside a C++ program?

    - by Dave K
    I have a Qt 4 GUI where I need to have a option in a drop-down menu that allows the user to choose to restart the computer. I realize this might seem redunant with the ability to restart the computer in other ways, but the choice needs to stay there. I've tried using system() to call the following: a suid-root shell script a non-suid shell script a suid-root binary program and all of them just cause reboot: must be superuser to be printed. Using system() to call reboot directly does the same thing. I'm not especially attached to using system() to do this, but it seemed like the most direct choice. How can I reboot the system from the GUI?

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  • Silently binding a variable instance to a class in C++?

    - by gct
    So I've got a plugin-based system I'm writing. Users can create a child class of a Plugin class and then it will be loaded at runtime and integrated with the rest of the system. When a Plugin is run from the system, it's run in the context of a group of plugins, which I call a Session. My problem is that inside the user plugins, two streaming classes called pf_ostream and pf_istream can be used to read/write data to the system. I'd like to bind the plugin instance's session variable to pf_ostream and pf_istream somehow so that when the user instantiates those classes, it's already bound to the session for them (basically I don't want them to see the session internals) I could just do this with a macro, wrapping a call to the constructor like: #define MAKE_OSTREAM = pf_ostream_int(this->session) But I thought there might be a better way. I looked at using a nested class inside Plugin wrapping pf_ostream but it appears nested classes don't get access to the enclosing classes variables in a closure sort of way. Does anyone know of a neat way to do this?

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  • best method in jquery for replacing rows in a table after server side processing such as mysql sorti

    - by Kevin J
    What is the 'best practice' when returning dynamic data for a table (server side sorting, filtering etc from a db) ? Do you return just the data in json, and repeatedly clone a row element, replacing the values in each row (thus decreasing the size of the ajax call, but increasing the client side processing), or return the full html, and replace with .html or .append? Or is there another method I'm missing? This is a frequent situation in my app, and in some cases a bottleneck, and I am unsure if what I am doing is the best solution. Currently, I return the row html and use a single .append call, after emptying all the rows except the header.

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  • Access to related Objects inside a model propery

    - by aliem
    Hi, I just run into some problems with django models. Example code is better than any word: class Cart(models.Model): updated_at = models.DateTimeField(auto_now=True) created_at = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'date %s;'%(self.created_at) def __str__(self): return self.__unicode__() def _total_items(self): """ Totale n di oggetti """ a = 0 for i in self.items.all: a += i.quantity return a total_items = property(_total_items) class Item(models.Model): cart = models.ForeignKey(Cart) quantity = models.PositiveIntegerField() def __unicode__(self): return u'product %s'%(self.id) def __str__(self): return self.__unicode__() but, when i call the cart property here's what i get in the python console: >>> a.total_items Traceback (most recent call last): File "<console>", line 1, in <module> File "models.py", line 49, in _total_items for i in self.item_set.all: TypeError: 'RelatedManager' object is not callable

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  • Simple Sinatra Ajax Not Working

    - by proteantech
    I was trying make an AJAX call from a static file on my computer to a simple sinatra service. The ajax call was returning with an error and no details. The server logged no errors either. Another strange symptom was that the Origin in the request header was null. I turns out that you can't make cross domain ajax calls without a little extra effort. You can set the Access-Control-Allow-Origin header on your sinatra response to expose your service to external domains using a snippet like this: get '/hi' do response['Access-Control-Allow-Origin'] = '*' content_type 'text/plain' "Hello World" end There's also another header you can set to allow other HTTP Methods besides gets, Access-Control-Request-Method. You can find more information by searching around for CORS: Cross Origin Resource Sharing and the previously mentioned headers. Oh, and in case you want to do this in Rails as well you can do something like this in your controller: after_filter :set_access_control_headers def set_access_control_headers headers['Access-Control-Allow-Origin'] = '*' headers['Access-Control-Request-Method'] = '*' end

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  • func_get_args detect context

    - by Steve
    I have a script where it accepts a varying number of arguments. I want to use func_get_args to perform operations on said arguments. If I have one function like this: function Something() { foreach(func_get_args($this) as $functions) { // Do something } // Return.. } I want to be able to call this function in, for example, another function to add/save entries. The add/save function would have arguments 'title', 'description' etc.. I basically want to know if there is a way to detect the context of a function call. Can I pass something to func_get_args that will let it know that its called in a certain function? So if I do: function Save($title, $desc) { $vars = $this->Something(); } I want $vars to contain $title and $desc after modifying them.

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  • Can't use method return value in write context; Not sure where to go from here

    - by Morgan Green
    This is my source for the variable. <?php if ($admin->get_permissions()=3) echo 'Welcome to the Admin Panel'; else echo 'Sorry, You do not have access to this page'; ?> And the code that I'm actually trying to call with the if statement is: public function get_permissions() { $username = $_SESSION['admin_login']; global $db; $info = $db->get_row("SELECT `permissions` FROM `user` WHERE `username` = '" . $db->escape($username) . "'"); if(is_object($info)) return $info->permissions; else return ''; } This should be a simple way to call my pages that the user is authorized for by using an else if statement. Or So I thought

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  • In Blackberry, how are shared objects in runtimestore recognized by other applications

    - by Carbonizer
    In Blackberry Runtime Store, when sharing objects between applications. How can we call methods of the shared object in another application, if the object itself is not recognized in the other application ? i am getting a runtime error when object gets typecasted, as that object is not defined in the calling applicatoin . If i typecast it to super interface and have the interface in another application. When i call getClass() on the object returned from the runtimestore. It shows as concrete class instance stored in the RunTimeStore. How can a share a object in runtimestore and use it across different applications ?

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  • [C++] Simple inheritance question

    - by xbonez
    I was going over some sample questions for an upcoming test, and this question is totally confusing me. Any help would be appreciated. Consider the following code: class GraduateStudent : public Student { ... }; If the word "public" is omitted, GraduateStudent uses private inheritance, which means which of the following? GraduateStudent objects may not use methods of Student. GraduateStudent does not have access to private objects of Student. No method of GraduateStudent may call a method of Student. Only const methods of GraduateStudent can call methods of Student.

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  • Low-overhead way to access the memory space of a traced process?

    - by vovick
    Hello all. I'm looking for an efficient way to access(for both read and write operations) the memory space of my ptraced child process. The size of blocks being accessed may vary from several bytes up to several megabytes in size, so using the ptrace call with PTRACE_PEEKDATA and PTRACE_POKEDATA which read only one word at a time and switch context every time they're called seems like a pointless waste of resources. The only one alternative solution I could find, though, was the /proc/<pid>/mem file, but it has long since been made read only. Is there any other (relatively simple) way to do that job? The ideal solution would be to somehow share the address space of my child process with its parent and then use the simple memcpy call to copy data I need in both directions, but I have no clues how to do it and where to begin. Any ideas?

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  • Trying to use a list iterator to print out entire linked list in Java. Infinite loop for some reaso

    - by Matt
    I created my list: private static List list = new LinkedList(); and my iterator: ListIterator itr = list.listIterator(); and use this code to try to print out the list... Only problem is, it never comes out of the loop. When it reaches the tail, shouldn't it come out of the loop, because there is no next? Or is it going back to the head like a circular linked list? It is printing so quickly and my computer locks up shortly after, so I can't really tell what is going on. while (itr.hasNext()) System.out.println(itr.next());

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  • Rails - Rendering a Partial without having to use "_" in front of the filename?

    - by bluedevil2k
    How do I render a partial without having to supply the "_" in front of the file name? Is there a parameter I can call to not use it? This problem popped up using RABL and Backbone - using RABL requires me to have a file in my views like "index.json.rabl". But, when I use embed the JSON right on the page load (as is usual with Backbone), I'm required to call the file "index.json.rabl". These 2 files are the exact same thing, just required to have different names. I'm looking to use just 1 file, "index.json.rabl" and force the render() function to look for that file name, without the "".

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  • checking the return code using python (MAC)

    - by cyberbemon
    I have written a script that checks if an SVN Repo is up and running, the result is based on the return value. import subprocess url = " validurl" def check_svn_status(): subprocess.call(['svn info'+url],shell=True) def get_status(): subprocess.call('echo $?',shell=True) def main(): check_svn_status() get_status() if __name__ == '__main__': main() The problem I'm facing is that if I change the url to something that does't exist I still get the return value as 0, but if I were to run this outside the script, i.e go to the terminal type svn info wrong url and then do a echo $? I get a return value of 1. But I can't re-create this in the python. Any guidelines ?

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  • C++ Questions about vectors

    - by xbonez
    Hey guys, I have a CS exam tomorrow. Just want to get a few questions cleared up. Thanks a lot, and I really appreciate the help. Que 1. What are parallel vectors? Vectors of the same length that contain data that is meant to be processed together Vectors that are all of the same data type Vectors that are of the same length Any vector of data type parallel Que 2. Arrays are faster and more efficient than vectors. True False Que 3. Arrays can be a return type of a function call. True False Que 4. Vectors can be a return type of a function call. True False

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  • How do I left pad a database column in FrontBase?

    - by PleaseStand
    I have a table of items (let's call it WIDGET) that each have their own eight-digit barcode numbers stored in a VARCHAR field (let's call it BARCODE; the table's primary key is in a separate integer field ID). My problem is that some personnel have omitted the leading zeros instead of entering the entire number while others have not. All new data is being entered with all eight digits present, but I would like to update all the existing records (several hundred in all) to eight digits for the sake of consistency. 1 → 00000001 234 → 00000234 5678 → 00005678 00009012 → 00009012 I know FrontBase supports all of SQL-92, but SQL-92 has no function specifically for left-padding strings. I already came up with a solution, but I am posting this question to see if anyone can think of a better way of doing this than I did.

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  • How to get all possible generic type in StructureMap?

    - by Soul_Master
    I just used StructureMap few days ago. I use StructureMap for collecting all validator class like the following code. public class BaseClassA {} public class ClassB : BaseClassA {} public class ClassC : BaseClassB {} public BaseClassAValidator : IValidator<BaseClassA>() {} In StructureMap, I only register IValidator interface for BaseClassAValidator class. But I want to get the same result when I call IValidator or IValidator that mean StructureMap should return IValidator where T is requested class or parent class of requested class. Is it possible? Or I need to manually call it.

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  • QuickTime movie disappearing from Javascript when scrolled offscreen in Firefox?

    - by c-had
    I have a web page I'm creating that uses Javascript to control an embedded QuickTime player. I add the QuickTime movie to the page using the AC_QuickTime.js file from Apple (as described here - http://developer.apple.com/mac/library/documentation/QuickTime/Conceptual/QTScripting_HTML/QTScripting_HTML_Document/ScriptingHTML.html#//apple_ref/doc/uid/TP40001525-2-SW1 ). Everything seems to be working fine - I can call methods on the QuickTime movie and control its playback (as well as get the current timestamp). The problem is that in Firefox, when I scroll down such that the QuickTime player is no longer visible, I get the following error every time I try to call a method on the QuickTime movie: Error calling method on NPObject! This does not occur in Safari. Why is this happening, and is there any way to work around this?

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • java.util.Observable, will clients complete executing their update() before continuing

    - by jax
    When I call: setChanged(); notifyObservers() on a java.until.Observable class, will all the listening Observer objects complete execution of their udpate() methods - assuming we are running in the same Thread - before the java.until.Observable class continues running? This is important because I will be sending a few messages through the notifyObservers(Object o) method in quick concession, it is important that each Observer class has finished its method before the new one though. I understand that the order of execution for each Observer class may vary when we call notifyObservers() - it is just important that the order of method execution for each individual instance is in order.

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  • Can I get parameter names/values procedurally from the currently executing function?

    - by Pwninstein
    I would like to do something like this: public MyFunction(int integerParameter, string stringParameter){ //Do this: LogParameters(); //Instead of this: //Log.Debug("integerParameter: " + integerParameter + // ", stringParameter: " + stringParameter); } public LogParameters(){ //Look up 1 level in the call stack (if possible), //Programmatically loop through the function's parameters/values //and log them to a file (with the function name as well). //If I can pass a MethodInfo instead of analyzing the call stack, great. } I'm not even sure what I want to do is possible, but it would be very nice to be able to automatically output parameter names/values at runtime to a file without explicitly writing the code to log them. Thanks!

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  • c# user notification while waiting

    - by user315445
    Hi, I am writing a simple win forms app in C#. There is a method call in my method which loads files but is taking a while to respond. Below is the method call Directory.GetFiles(selectedFolder, "*.xml", SearchOption.AllDirectories); I want to notify this to users. Is there a way to show them that file loading is in progress? I want a simplest way. I suppose Splash screen is too costly for my app. Thanks, Sid

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