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• C++ volatile required when spinning on boost::shared_ptr operator bool()?

  - by JaredC

  I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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• simple GET validation

  - by Andrew

  I have GET[] input and would like to carry out their validation. The input data is always a number by. Schema. I want to make sure that the pass number and the appropriate amount - not to throw the sql query. at this moment I am using the procedures $cc = $_GET['cc']; if ($cc=='') $cc='9012';$find=array("..", "/", "\\"); $replace=array("", "", ""); $cc=str_replace($find, $replace, $cc); $eic = $_GET['eic']; .... ect. // where f.ex. 9012 is an real existing data (in dbase) to generate sucure sql question GET[] variable data schema $_GET[$cc] - always 4 digits $_GET[$eic] - always 4 digits $_GET[$iy] - always 4 digits $_GET[$ir] - always 1 digit Can you show me a better way to secure my GET?

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• addslashes and addcslahes

  - by theband

  I was seeing today the addslashes and addcslashes in php.net, but did not get the point on what is the difference between them and what are the characters escaped in these two. <?php $originaltext = 'This text does NOT contain \\n a new-line!'; $encoded = addcslashes($originaltext, '\\'); $decoded = stripcslashes($encoded); //$decoded now contains a copy of $originaltext with perfect integrity echo $decoded; //Display the sentence with it's literal \n intact ?> If i comment the $decoded variable and echo $encoded, i get the same value which is in the original string. Can anyone clearly explain me the difference and use of these two.

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• Passing a String from PHP to a JavaScript function

  - by user635614

  Hello. am trying to write a code to pass a php string when clicked on the table : <?php . . . echo("<td onclick = 'print_("$file[$i]->Name");' >". $files[$i]->Name."</td>"); ... ?> where files[] is an array, and each element is a class with Name as a String, and it is put in a ''for'' loop, Am trying to pass it to a JavaScript function where i need the name there,and it's not working,i tried passing the i variable and it was passed correctly so i thought there should be a special syntax for dealing with strings... function print_(var x) { alert(x);}

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• can we write this in C++ switch ?

  - by jellly

  #include <iostream> using namespace std; int main(){ char i; cin >>i; switch (i){ case ('e'||'i'||'o'||'u'||'a'): cout<<"Vowel"; break; case ('+'||'-'||'/'||'*'||'%'): cout<<"Op"; break; } return 0; } if not than how can we use comparison or logical operators in switch ? & why cant we declare and initialize variable in single case without using scope ?

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• Is it possible to have a variadic function in C with no non-variadic parameter?

  - by Tim

  I have the following function: void doStuff(int unusedParameter, ...) { va_list params; va_start(params, unusedParameter); /* ... */ va_end(params); } As part of a refactor, I'd like to remove the unused parameter without otherwise changing the implementation of the function. As far as I can tell, it's impossible to use va_start when you don't have a last non-variadic parameter to refer to. Is there any way around this? Background: It is in fact a C++ program, so I could use some operator-overloading magic as suggested here, but I was hoping not to have to change the interface at this point. The existing function does its work by requiring that the variable argument list be null-terminated, and scanning for the NULL, therefore it doesn't need a leading argument to tell it how many arguments it has.

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• the use of private keyword

  - by LAT

  Hi everyone I am new to programming. I am learning Java now, there is something I am not really sure, that the use of private. Why programmer set the variable as private then write , getter and setter to access it. Why not put everything in public since we use it anyway. public class BadOO { public int size; public int weight; ... } public class ExploitBadOO { public static void main (String [] args) { BadOO b = new BadOO(); b.size = -5; // Legal but bad!! } } I found some code like this, and i saw the comment legal but bad. I don't understand why, please explain me.

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• Function argument treated as undeclared

  - by Mikulas Dite

  I've prepared this simple example which is not working for me #include <stdio.h> #include <stdlib.h> FILE *fp; char filename[] = "damy.txt"; void echo (char[] text) { fp = fopen(filename, "a"); fwrite(text, 1, strlen(text), fp); fclose(fp); printf(text); } int main () { echo("foo bar"); return 0; } It's supposed to write both to command window and to file. However, this gives compilation error - the text used in echo() is not declared. Does c need another declaration of the variable?

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• More elegant way to initialize list of duplicated items in Python

  - by Claudiu

  If I want a list initialized to 5 zeroes, that's very nice and easy: [0] * 5 However if I change my code to put a more complicated data structure, like a list of zeroes: [[0]] * 5 will not work as intended, since it'll be 10 copies of the same list. I have to do: [[0] for i in xrange(5)] that feels bulky and uses a variable so sometimes I even do: [[0] for _ in " "] But then if i want a list of lists of zeros it gets uglier: [[[0] for _ in " "] for _ in " "] all this instead of what I want to do: [[[0]]*5]*5 Has anyone found an elegant way to deal with this "problem"?

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• PHP and Java interoperablity

  - by Jack

  I am working on windows using tomcat 6 and PHP/Java Bridge. I know how to access a Java file from PHP but how do we do it the other way i.e accessing PHP from Java <?php require_once("java\Java.inc"); $systemInfo = new Java("java.lang.System"); print "Total seconds since January 1, 1970: ".$systemInfo->currentTimeMillis(); ?> Also how do I access Java classes that are created by me. Do I write a CLASSPATH env variable or change the php.ini config file?

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• Should member variables of global objects be made global as well?

  - by David Wong

  I'm developing plugins in Eclipse which mandates the use of singleton pattern for the Plugin class in order to access the runtime plugin. The class holds references to objects such as Configuration and Resources. In Eclipse 3.0 plug-in runtime objects are not globally managed and so are not generically accessible. Rather, each plug-in is free to declare API which exposes the plug-in runtime object (e.g., MyPlugin.getInstance() In order for the other components of my system to access these objects, I have to do the following: MyPlugin.getInstance().getConfig().getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); , which is overly verbose IMO. Since MyPlugin provides global access, wouldn't it be easier for me to just provide global access to the objects it manages as well? MyConfig.getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); Any thoughts? (I'm actually asking because I was reading about the whole "Global variable access and singletons are evil" debates)

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• Objective-C : Changing "self" value inside self

  - by Oliver

  Hello, I have a category on NSDate, and I want to implement some functions to manipulate the date, like : NSDate *thedate = [NSDate date]; [thedate setToMidnight]; so I have a function in NSDate like : -(void)setToMidnight { some code with calendars and comps self = theNewDate; } This works inside the function, but outside this member function, thedate has not changed. I understand this malfunction because I've been told that self is just a local variable created inside the member function. So, how can I make this work ? Of course, I could have written : thedate = [thedate dateAsMidnightDate] or thedate = [NSDate dateAtMidnightFromDate:thedate] but I feel it has more sense inside the instance class, as I don't want to change the date but just adjust some values of the previously created one. Can you help me to achieve this ?

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• Extending appengine's db.Property with caching

  - by Noio

  I'm looking to implement a property class for appengine, very similar to the existing db.ReferenceProperty. I am implementing my own version because I want some other default return values. My question is, how do I make the property remember its returned value, so that the datastore query is only performed the first time the property is fetched? What I had is below, and it does not work. I read that the Property classes do not belong to the instances, but to the model definition, so I guess that the return value is not cached for each instance, but overwritten on the model every time. Where should I store this _resolved variable? class PageProperty(db.Property): data_type = Page def get_value_for_datastore(self, model_instance): page = super(PageProperty, self).get_value_for_datastore(model_instance) self._resolved = page return page.key().name() def make_value_from_datastore(self, value): if not hasattr(self, '_resolved'): self._resolved = Page.get_by_name(value) return self._resolved

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• Whats the best to way convert a set of Java objects to another set of objects?

  - by HDave

  Basic Java question here from a real newbie. I have a set of Java objects (of class "MyClass") that implement a certain interface (Interface "MyIfc"). I have a set of these objects stored in a private variable in my class that is declared as follows: protected Set<MyClass> stuff = new HashSet<MyClass>(); I need to provide a public method that returns this set as a collection of objects of type "MyIfc". public Collection<MyIfc> getMyStuff() {...} How do I do the conversion? The following line gives me an error that it can't do the conversion. I would have guessed the compiler knew that objects of class MyClass implemented MyIfc and therefore would have handled it. Collection<MyIfc> newstuff = stuff; Any enlightenment is appreciated.

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• JAVA: How do I accept input during a certain period of time only

  - by sebrock

  Im trying to do a simple game where I continually need input from players. This needs to happen during a certain time period only. Everything that is sent after that will be discarded. After the time period a new game starts. So: Start game Wait for input from all players during 10 seconds 10 secs no more input Calculate the winner and do some stuff Goto 1. I was thinking using a timer and timertask to keep track of time and maybe use a boolean variable that changes from "open" to "closed" after 10 seconds? Please give me some advise on this.

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• How do I replace "this" in Java with something that works.

  - by Luke Alderton

  I'm looking to get the showGUI() method work, the compiler says "this" is not a static variable and cannot be referenced from a static context, what would I use to replace "this"? I've tried test.main (test being the package it's in). The reason I'm using the static method showGUI() is because I need the method to be called from another static method, as well as the startup() method. Below are my two main classes. public class Main extends SingleFrameApplication { @Override protected void startup() { showGUI(); } @Override protected void configureWindow(java.awt.Window root) { } public static Main getApplication() { return Application.getInstance(Main.class); } public static void main(String[] args) { launch(Main.class, args); } public static void showGUI() { show(new GUI(this)); } } public class GUI extends FrameView { public GUI(SingleFrameApplication app) { super(app); initComponents(); } private void initComponents() { //all the GUI stuff is somehow defined here } }

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• that, self or me — which one to prefer in JavaScript?

  - by Török Gábor

  While coding JavaScript sometimes you store the reference of object this in a local variable for different purposes (to set proper scope, to help code obfuscators, etc.). There are coders who prefer aliasing this to that to make it obvious its intention. Other guys use self since it's pointing to the object itself. I even saw source codes where me held the reference and it still makes sense. Certainly there are other ones. Which one should I prefer? Is there a convention on which to use or is it only the matter of taste.

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• it is possible to "group by" without losing the original rows?

  - by toPeerOrNotToPeer

  i have a query like this: ID | name | commentsCount 1 | mysql for dummies | 33 2 | mysql beginners guide | 22 SELECT ..., commentsCount // will return 33 for first row, 22 for second one FROM mycontents WHERE name LIKE "%mysql%" also i want to know the total of comments, of all rows: SELECT ..., SUM(commentsCount) AS commentsCountAggregate // should return 55 FROM mycontents WHERE name LIKE "%mysql%" but this one obviously returns a single row with the total. now i want to merge these two queries in one single only, because my actual query is very heavy to execute (it uses boolean full text search, substring offset search, and sadly lot more), then i don't want to execute it twice is there a way to get the total of comments without making the SELECT twice? !! custom functions are welcome !! also variable usage is welcome, i never used them...

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• android: getting rid of "warning: unmappable character for encoding ascii"

  - by Lo'oris

  I'm compiling using android tools without eclipse. I compile launching "ant debug" from command line. I have found many many instructions around the web about how to remove with annoying warning, but I haven't been able to make any of them work. I've tried -D option, I've tried randomly tweaking build.* files, I've tried exporting an environment variable... nothing. I guess some of these methods just don't work, and some others would work but I've been doing them incorrectly. Anything is possible and I can't stand it any more: any advice on how to do it?

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• How to access a method of a closure's parent object?

  - by Bytecode Ninja

  I have defined a class named MyClass and I have defined two methods myMethod1 and myMethod2 for it: function MyClass() {} MyClass.prototype.myMethod1 = function() {...}; MyClass.prototype.myMethod2 = function() {...}; Inside myMethod1, I use jQuery and there's a callback closure defined there: MyClass.prototype.myMethod2 = function() { $.jQuery({success: function(data) { this.myMethod2(); }, ...}); } Now the problem is that this no longer is referring to MyClass. The question is how can I refer to it? At the moment I have assigned it to a variable named thisObj and access it this way: MyClass.prototype.myMethod2 = function() { var thisObj = this; $.jQuery({success: function(data) { thisObj.myMethod2(); }, ...}); } Is there a better way to access MyClass.this from the closure nested in myMethod2? Thanks in advance.

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• How do you extend a Ruby module with macro-like metaprogramming methods?

  - by Ian Terrell

  Consider the following extension (the pattern popularized by several Rails plugins over the years): module Extension def self.included(recipient) recipient.extend ClassMethods recipient.class_eval { include InstanceMethods } end module ClassMethods def macro_method puts "Called macro_method within #{self.name}" end end module InstanceMethods def instance_method puts "Called instance_method within #{self.object_id}" end end end If you wished to expose this to every class, you can do the following: Object.send :include, Extension Now you can define any class and use the macro method: class FooClass macro_method end #=> Called macro_method within FooClass And instances can use the instance methods: FooClass.new.instance_method #=> Called instance_method within 2148182320 But even though Module.is_a?(Object), you cannot use the macro method in a module: module FooModule macro_method end #=> undefined local variable or method `macro_method' for FooModule:Module (NameError) This is true even if you explicitly include the original Extension into Module with Module.send(:include, Extension). How do you add macro like methods to Ruby modules?

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• Django m2m adding field in the secondary table

  - by dana

  I have a model in wich i'm using m2m Django ORM feature, in order to create an aditional table to hold my 'classrom members'. My problem is: the membership to a classroom must be accepted by the invited one, so i need a boolean field :1=accepted, 0=refused/unseen yet. How can i include this boolean variable in the aditionally generated classroom_membership (and NOT in the primary created Classroom table)? class Classroom(models.Model): user = models.ForeignKey(User, related_name = 'classroom_creator') classname = models.CharField(max_length=140, unique = True) date = models.DateTimeField(auto_now=True) open_class = models.BooleanField(default=True) #domain = models.EnumField() members = models.ManyToManyField(User,related_name="list of invited members") Thanks in advance!!

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• pthread_exit return value

  - by Manty

  This is surprising for me. void * thread_func(void *arg) { pthread_exit(&ret); } int main(void) { pthread_t thr; int *exit_status; pthread_create(&thr, NULL, thread_func, NULL); sleep(2); pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); ret = 20; pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); return 0; } The output is value of exit status - 50 value of exit status - 20 I was expecting both the times the exit_status would be the actual exit value(50 in my case) of the thread. Instead it is just returning the value of the global variable which I used for pthread_exit. Is it not a bug?

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• Declared Properties and assigning values with self

  - by Shaun Budhram

  I understand how declared properties work - I just need a clarification on when Objective C is using the accessor method vs. when it is not. Say I have a property declared using retain: @property (nonatomic, retain) NSDate *date; ... and later... @synthesize date If I say: date = x Is that calling the accessor method? Or is it just setting the variable? self.date = x This seems to call the accessor method (I think but I'm not sure, since it seems like the retain count is increasing). Can anyone clarify this issue? I'm curious because i have some variables that seem to become invalid before I need them (and I have to specifically call retain), and I suspect this is why.

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