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  • Dangling pointers and double free

    - by user151410
    After some painful experiences, I understand the problem of dangling pointers and double free. I am seeking proper solutions. aStruct has a number of fields including other arrays. aStruct *A=NULL, *B = NULL; A = (aStruct*) calloc(1, sizeof(sStruct)); B = A; free_aStruct(A); ... //bunch of other code in various places. ... free_aStruct(B); Is there any way to write free_aStruct(X) so that free_aStruct(B) exists gracefully?? void free_aStruct(aStruct *X){ if (X ! = NULL){ if (X->a != NULL){free(X->a); x->a = NULL;} free(X); X = NULL; } } Doing above only sets A = NULL when free_aStruct(A); is called. B is now dangling. How can this situation be avoided / remedied? Is reference counting the only viable solution? or, are there other "defensive" free approaches, to prevent free_aStruct(B); from exploding? Thanks, Russ

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  • Trial vs free with limited functionality

    - by Morten K
    Hi everyone, Not a programming question as such, but a bit more business oriented question about software product development. We have just released a small app, and is offering a free, fully functional trial which lasts for 15 days. I have the gut feeling however, that to reach any kind of penetration on the web, we'd need to offer a version which is free forever, but then has a few limitations in terms of functionality (still quite usable, but not full-throttle). For example, the Roboform browser plugin is somewhat similar in purpose to ours. Not functionality wise, but it's basically a little util that saves time and removes some repetitive-action pain. They offer a free version with limitations and then a pro version for around 30 USD. Roboform has gotten very much attention over the years, and I can't help to think that this is because they have a product which is obviously good, but also free, thus adoption becomes much higher than if they had only offered a 15 day trial. I am wondering if any of you have experience in a similar scenario? Or any thoughts on the two models? Again, I know it's not directly programming related, but it's still a question I feel best answered by a community of developers.

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  • Number of Classes in a Namespace - Code Smell?

    - by Tim Claason
    I have a C# library that's used by several executables. There's only a couple namespaces in the library, and I just noticed that one of the namespaces has quite a few classes in it. I've always avoided having too many classes in a single namespace because of categorization, and because subconsciously, I think it looks "prettier" to have a deeper hierarchy of namespaces. My question is: does anyone else consider it a "code smell" when a namespace has many classes - even if the classes relate to each other? Would you put in a lot of effort to find nuances in the classes that allows for subcategorization?

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  • How should I handle "real time" events in an online strategy game?

    - by Hojat Taheri
    Some online strategy games have real time events. For example when you send troops to attack somewhere, the attack happens at the right time in the future. Checking the database again and again to get the list of attacks happening each second would cause heavy load. Is there any technique to achieve this goal? Another example: You want to attack a village 3 hours away, you send troops and the attack occurs 3 hours later. Should there be an script to check the database at each second to run the query at the specified time?

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  • Should concrete classes avoid calling other concrete classes, except for data objects?

    - by Kazark
    In Appendix A to The Art of Unit Testing, Roy Osherove, speaking about ways to write testable code from the start, says, An abstract class shouldn't call concrete classes, and concerete classes shouldn't call concrete classes either, unless they're data objects (objects holding data, with no behavior). (259) The first half of the sentence is simply Dependency Inversion from SOLID. The second half seems rather extreme to me. That means that every time I'm going to write a class that isn't a simple data structure, which is most classes, I should write an interface or abstract class first, right? Is it really worthwhile to go that far in defining abstract classes an interfaces? Can anyone explain why in more detail, or refute it in spite of its benefit for testability?

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  • what are the "Online accounts" used for under System Settings?

    - by user67811
    I previously never bothered with it. but I just did a fresh install of 12.04 and figured "hey maybe i'll put in my google account and see what happens" I logged in with google and everyting like mal/calendar/contacts/chat is set to "on"... I figured it might automatically set up my gmail for various applications like empathy and thunderbird.. but I opened them up and found nothing... What exactly is the purpose of adding your account to "online accounts"? where is it used?

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  • Online DATAFILE MOVE in Oracle Database 12c

    - by Ulrike Schwinn (DBA Community)
    Einige Operationen im Datenbankumfeld können nicht nur offline sondern auch online durchgeführt werden. Ein wichtiges Kennzeichen einer Online Operation ist dabei, dass Abfragen und DML Operationen während des Ablaufs der Operation (beispielsweise einer Reorganisation) ohne Unterbrechung weiter laufen können. Je nach einplanbarer Maintenance Zeit ist es daher durchaus wünschenswert, gewisse Operationen online durchzuführen. Generell gibt es in jedem Datenbankrelease einige Erweiterungen im Umfeld von Online Operationen. Besonders im aktuellen Release 12c gibt es eine Vielzahl neuer Operationen zu diesem Thema.Während der ersten 12c Veranstaltungen fand besonders das Kommando "DATAFILE ONLINE MOVE" besondere Aufmerksamkeit bei vielen Kunden. Aus diesem Grund wird im aktuellen Tipp dazu eine kleine Einführung gegeben.  Mehr dazu erfahren Sie hier. 

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  • C Programming: malloc and free within a loop

    - by kouei
    Hi all, I just started out with C and have very little knowledge about performance issues with malloc() and free(). My question is as such: if I were to call malloc() followed by free() in a while-loop that loops for, say, 20 times, would it run slower compared to if I were to call free() outside the loop? I am actually using the first method to allocate memory to a buffer, read a string of variable length in a file, perform some string operation, and then clear the buffer after every iteration. If my method results in a lot of overhead then I'd like to ask for a better way for me to achieve the same results. Sorry for my bad English. Thanks and regards, K

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  • "Arbitrary" context free grammars?

    - by danwroy
    Long time admirer first time inquirer :) I'm working on a program which derives a deterministic finite-state automata from a context-free grammar, and the paper I have been assigned which explains how to do this keeps referring to "arbitrary probabilistic context-free grammars" but never defines the meaning of "arbitrary" in relation to PCFGs. I assume they mean "any old PCFG" but then why not just say "any PCFG"? The term also turns up in several Wikipedia entries. At the top of the CFG page there is a reference to arbitrariness in relation to CFGs on ("clauses can be nested inside clauses arbitrarily deeply"), but doesn't make clear why someone would refer to a PCFG or subset of PCFGs as arbitrary. In case anyone is curious, the paper is Parsing and Hypergraphs by Klein and Manning (2001); I've also been reading two other papers by them related to this one (An Agenda-Based Chart Parser for Arbitrary Probabilistic Context-Free Grammars and Empirical Bounds, Theoretical Models, and the Penn Treebank) which use the term extensively but never explain it either. Thanks for your help!

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  • How does C free() work?

    - by slee
    #include <stdio.h> #include <stdlib.h> int * alloc() { int *p = (int *)calloc(5,4); printf("%d\n",p); return p; } int main() { int *p = alloc(); free(p); printf("%d\n",p); p[0] = 1; p[1] = 2; printf("%d %d\n",p[0],p[1]); } As to the code segment, I allocate 5 ints,first. And then I free the memory. When I printf p, why does p sill have a value same to the memory address allocated first? And I also can assign value to p[0] and p[1]. Does this mean free() do nothing? Once I allocate memory, I can use later though I have freed it.

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  • WinForm partial classes

    - by nivlam
    I have a WinForm project that contains a form called MainUI. You can see that the automatically generated partial class shows up as a node under MainUI.cs. Is there a way to "move" my self created partial class MainUI.Other.cs under MainUI.cs so that it'll show as another node?

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  • Python: combining making two scripts into one

    - by Alex
    I have two separately made python scripts one that makes a sine wave sound based off time, and another that produces a sine wave graph that is based off the same time factors. I need help combining them into one running file. Here's the first: from struct import pack from math import sin, pi import time def au_file(name, freq, freq1, dur, vol): fout = open(name, 'wb') # header needs size, encoding=2, sampling_rate=8000, channel=1 fout.write('.snd' + pack('>5L', 24, 8*dur, 2, 8000, 1)) factor = 2 * pi * freq/8000 factor1 = 2 * pi * freq1/8000 # write data for seg in range(8 * dur): # sine wave calculations sin_seg = sin(seg * factor) + sin(seg * factor1) fout.write(pack('b', vol * 64 * sin_seg)) fout.close() t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis * 100 tim = float(ti) tim = tim * 100 if __name__ == '__main__': au_file(name='timeSound.au', freq=tim, freq1=tis, dur=1000, vol=1.0) import os os.startfile('timeSound.au') and the second is this: from Tkinter import * import math import time t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis / 100 tim = float(ti) tim = tim / 100 root = Tk() root.title("This very moment") width = 400 height = 300 center = height//2 x_increment = 1 # width stretch x_factor1 = tis x_factor2 = tim # height stretch y_amplitude = 50 c = Canvas(width=width, height=height, bg='black') c.pack() str1 = "sin(x)=white" c.create_text(10, 20, anchor=SW, text=str1) center_line = c.create_line(0, center, width, center, fill='red') # create the coordinate list for the sin() curve, have to be integers xy1 = [] xy2 = [] for x in range(400): # x coordinates xy1.append(x * x_increment) xy2.append(x * x_increment) # y coordinates xy1.append(int(math.sin(x * x_factor1) * y_amplitude) + center) xy2.append(int(math.sin(x * x_factor2) * y_amplitude) + center) sinS_line = c.create_line(xy1, fill='white') sinM_line = c.create_line(xy2, fill='yellow') root.mainloop()

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  • How to add CSS classes to Zend_Form_Element_Select option

    - by Jah Selassie
    Hi, I'm trying to add a CSS class to a Zend_Form_Element_Select option, but I just can't find a way to do it. The desired output would be something like this: <select name="hey" id="hey"> <option value="value1" style="parent">label1</option> <option value="value2" style="sibling">sublabel1</option> <option value="value3" style="sibling">sublabel2</option> <option value="value4" style="parent">label2</option> <option value="value5" style="sibling">sublabel3</option> <option value="value6" style="sibling">sublabel4</option> </select> But I'm getting this: <select name="hey" id="hey"> <option value="value1">label1</option> <option value="value2">sublabel1</option> <option value="value3">sublabel2</option> <option value="value4">label2</option> <option value="value5">sublabel3</option> <option value="value6">sublabel4</option> </select> I can't seem to pass a CSS class attribute to any of the options in the select element although I can style the select element itselft. My code: $sel = new Zend_Form_Element_Select('hey'); $sel->setRequired(true)->setLabel('Select an Option:'); $sel->addMultiOption('value1', 'label1', array('class' => 'parent')) ->addMultiOption('value2', 'sublabel1', array('class' => 'sibling')) (etc...); After researching a bit I found out that Element_Select doesn't have a method for adding CSS styles to the options in the select box, only for the select itself. So, how can I add them? Should I extend the form_element_select? Or would a custom decorator suffice? Can anyone give me a hint? I'm baffled with this. Thanks in advance!

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  • Slider value available between different cocoa classes

    - by Miguel Bayona
    I am playing around with an iPhone app, and need to accomplish something that I am sure is very basic: I have a slider that is implemented in a Controller.m class. However, I need its value must be available in a different class, MainView.m class where I have defined an equation that depends on the value of the slider. How can I do it?? Thanks, Miguel Bayona

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  • Mingling C++ classes with Objective C classes

    - by Joey
    I am using the iphone SDK and coding primarily in C++ while using parts of the SDK in obj-c. Is it possible to designate a C++ class in situations where an obj-c class is needed? For instance: 1) when setting delegates to obj-c objects. I cannot make a C++ class derive from a Delegate protocol so this and possibly other reasons prevent me from making my C++ class a delegate for various obj-c objects. What I do as a solution is create an obj-c adapter class that contains a ptr to the C++ class and is used as the delegate (notifying the C++ class when it is called). It feels cumbersome to write these every time I need to get delegate notifications to a C++ class. 2) when setting selectors This goes hand in hand with item 1. Say I want to set a callback to fire when something is done, like a button press or a setAnimationDidStopSelector in the UIView animation functionality. It would be nice to be able to designate a C++ function along with the relevant delegate for setAnimationDelegate. Well, I suspect this isn't readily possible, but if anyone has any suggestions on how to do it if it is, or on how to write such things more easily, I would love to hear them. Thanks.

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  • C++ Beginner - Trouble using classes inside of classes

    - by Francisco P.
    Hello, I am working on a college project, where I have to implement a simple Scrabble game. I have a player class (containing a Score and the player's hand, in the form of a std::string, and a score class (containing a name and numeric (int) score). One of Player's member-functions is Score getScore(), which returns a Score object for that player. However, I get the following error on compile time: player.h(27) : error C2146: syntax error : missing ';' before identifier 'getScore' player.h(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(27) : warning C4183: 'getScore': missing return type; assumed to be a member function returning 'int' player.h(35) : error C2146: syntax error : missing ';' before identifier '_score' player.h(35) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int player.h(35) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int Here's lines 27 and 35, respectively: Score getScore(); //defined as public (...) Score _score; //defined as private I get that the compiler is having trouble recognizing Score as a valid type... But why? I have correctly included Score.h at the beginning of player.h: #include "Score.h" #include "Deck.h" #include <string> I have a default constructor for Score defined in Score.h: Score(); //score.h //score.cpp Score::Score() { _name = ""; _points = 0; } Any input would be appreciated! Thanks for your time, Francisco EDIT: As requested, score.h and player.h: http://pastebin.com/3JzXP36i http://pastebin.com/y7sGVZ4A

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  • Changing classes on multiple divs when selecting specific radio buttons

    - by Rob
    Hey everyone I got a javascript problem I can't seem to find a specific solution for on the web. What I want to be able to do is select one of the radio buttons and have that change the class of #home-right to either .rackmount or .shipping and add the class of .displaynone to the type of dimensions I don't want shown. <div id="home-right" class="rackmount"> <h4 class="helvneuebcn">Case Finder</h4> <div class="cta-options"> <input type="radio" value="Shipping and Storage" name="" checked> Shipping and Storage<br/> <input type="radio" value="Rackmount Enclosures" name=""> Rackmount Enclosures<br/> </div> <div class="shipping-dimensions displaynone"> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">H x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">W x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">L</span></div> </div> <div class="rackmount-dimensions"> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">U Height x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">Rack Depth</span></div> </div> <div class="clear"></div> <input type="button" value="Submit" class="findcase"> </div>

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  • What are guard methods/classes?

    - by Paul Sasik
    i just noticed the guard method/class mentioned in this question and i don't really get the concept from the answers. And alas, Jon Skeet's link to an MS site never loaded. A few quick Google searches seemed to yield only products, not software engineering concepts. Any explanation and/or samples would be appreciated. (Especially from the .Net side of things.)

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  • Wordpress sidebar classes

    - by Chris J. Lee
    There any way i could add a class for the specific order of widget item? i.e. the class name would be widgetorder-1 (for the first appearing widget), widgetorder-2 (for the widget appearing in the 2nd order), etc. I looked into filters but wasn't sure how that worked.

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  • Delphi, VirtualStringTree - classes (objects) instead of records

    - by michal
    I need to use a class instead of record for VirtualStringTree node. Should I declare it standard (but in this case - tricky) way like that: PNode = ^TNode; TNode = record obj: TMyObject; end; //.. var fNd: PNode; begin fNd:= vstTree.getNodeData(vstTree.AddChild(nil)); fNd.obj:= TMyObject.Create; //.. or should I use directly TMyObject? If so - how?! How about assigning (constructing) the object and freeing it? Thanks in advance m.

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  • Multiple classes in Codeigniter

    - by Leon
    I want to create an array of objects, so what I did was to create a library but I can't figure out how to actually dynamically create instances of it in a loop and store each instance in an array. Can anyone tell me please?

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  • Disturbing or politically incorrect classes

    - by Jonas B
    Please don't take this seriously! - Community wikied Satire is always fun. Try to come up with the most shocking, disturbing or politically incorrect class you can think of. (But please no racism or anything seriously offensive or anything that can't be interpeted as satire). I'll go first with my example: public class Person { public bool Female; public Person(bool female) { Female = female; } public static bool operator <(Person j1, Person j2) { if (j1.Female && !j2.Female) return true; else return false; } public static bool operator >(Person j1, Person j2) { if (!j1.Female && j2.Female) return true; else return false; } public static bool operator <=(Person j1, Person j2) { if ((j1.Female == j2.Female) || (j1.Female && !j2.Female)) return true; else return false; } public static bool operator >=(Person j1, Person j2) { if ((j1.Female == j2.Female) || (!j1.Female && j2.Female)) return true; else return false; } }

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  • Are there any online database schema drawing tools?

    - by Pure.Krome
    Hi folks, i wish to draw up some database schemas. Eg, table 1 has zero to many rows in table 2, etc. It's purely for visual purposes (eg. no sql code, etc). Are there any online tools / website that offer this? (please don't say: Use Sql Server Database Diagrams, print screen, upload to image hosting service). thanks :) EDIT: Please take note of the keyword - ONLINE. I don't want any desktop solutions (because I already have one of these).

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