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  • Any good idioms for error handling in straight C programs?

    - by Will Hartung
    Getting back in to some C work. Many of my functions look like this: int err = do_something(arg1, arg2, arg3, &result); With the intent the result gets populated by the function, and the return value is the status of the call. The darkside is you get something naive like this: int err = func1(...); if (!err) { err = func2(...); if (!err) { err = func3(...); } } return err; I could macro it I suppose: #define ERR(x) if (!err) { err = (x) } int err = 0; ERR(func1(...)); ERR(func2(...)); ERR(func3(...)); return err; But that only works if I'm chaining function calls, vs doing other work. Obviously Java, C#, C++ have exceptions that work very well for these kinds of things. I'm just curious what other folks do and how other folks do error handling in their C programs nowadays.

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  • C++ operator[] syntax.

    - by Lanissum
    Just a quick syntax question. I'm writing a map class (for school). If I define the following operator overload: template<typename Key, typename Val> class Map {... Val* operator[](Key k); What happens when a user writes: Map<int,int> myMap; map[10] = 3; Doing something like that will only overwrite a temporary copy of the [null] pointer at Key k. Is it even possible to do: map[10] = 3; printf("%i\n", map[10]); with the same operator overload?

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  • Can I reproduce Scala's behavior for == ?

    - by JPP
    In Programming in Scala, I can read that the == operator behaves as if it was defined like this: final def == (that: Any): Boolean = if (null eq this) {null eq that} else {this equals that} But there must actually be compiler magic to avoid null pointer exceptions, right? Is there any way for me to replicate this behavior with pure Scala; i.e., have an operator/method return one thing if the receiver is null and another one if it isn't? What I mean is an actual implementation of null eq this. I suppose I can write a "pimp" and then define the method on the wrapper class, but is there a more direct way to do this?

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  • [PHP] Variables loaded from a separate script are not defined within functions

    - by Goro
    Hello, I use settings.php to store general settings for my application. When I load this settings file, I can use the variables defined in settings.php in the script itself, but not within any functions I define in it. For example, in my class definition, myclass.php: <?php $preIP = dirname(__FILE__); require_once( "preIP/settings.php" ); class MyClass { ... public function foo() { echo $variable_from_settings; } } The code in the function foo() will not work (the variable will not be defined). The settings.php file looks like this: $variable_from_settings = "bar"; Thanks,

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  • Books/resources for help with extracting useful feedback from clients?

    - by Eric
    I'm a web application developer looking for a book or something similar that can help with effectively communicating with clients who have a very vague or unrealistic idea of what they'd like out of the work I'm doing. Some fictional, though not by much, examples of situations: Clients who are not familiar with using the Internet, and insist on features that are not even remotely feasible (ex. time travel) Clients who are unable to express accurately what they're looking for (ex. "I know that's what I said and signed off on, but it's not what I meant") Clients who refuse to attend meetings or review sessions to answer questions or define requirements (which makes any agile development impossible) For the most part, I'm trying to find best practices for how to handle these kinds of things on a team-building level. The best ways to effectively address serious project roadblocks without sounding like a total jerk. Any recommendations for reading material on this topic?

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  • Array-size macro that rejects pointers

    - by nneonneo
    The standard array-size macro that is often taught is #define ARRAYSIZE(arr) (sizeof(arr) / sizeof(arr[0])) or some equivalent formation. However, this kind of thing silently succeeds when a pointer is passed in, and gives results that can seem plausible at runtime until things mysteriously fall apart. It's all-too-easy to make this mistake: a function that has a local array variable is refactored, moving a bit of array manipulation into a new function called with the array as a parameter. So, the question is: is there a "sanitary" macro to detect misuse of the ARRAYSIZE macro in C, preferably at compile-time? In C++ we'd just use a template specialized for array arguments only; in C, it seems we'll need some way to distinguish arrays and pointers. (If I wanted to reject arrays, for instance, I'd just do e.g. (arr=arr, ...) because array assignment is illegal).

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  • How To Securly Store Data In MySQL Using AES_ENCRYPT

    - by Justin
    We are storing sensitive data in MySQL, and I want to use AES_ENCRYPT(data, 'my-secret-key-here') which works great. My biggest question is how do I secure the key? Previously I just wast storing the key in a web PHP file, so something like: define("ENCRYPTION_KEY", 'my-secret-key-here'); This really doesn't work though, as our MySQL server and web server are the same physical machine, so if somebody gains access to the server, they can get both the encrypted data stored in MySQL and the key. Any ideas? I am thinking I need to move the key to a separate server, and read it in remotely. Or, what about generating the encryption key dynamically for each piece of data. For example taking the customer_id and running md5 on it, and then using that as the key.

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  • facelet - nested <ui:insert>

    - by user321350
    I have multiple templates which differs with each other only by few containers. The most complex one contains superset of all containers used in all other one thus to avoid creating multiple templates I created the most complex one in following format some layout stuff (div and all) defining nested insert for each container and content. Now in client template based on what is needed I turn off container which is not needed as else if container is needed, just define content as doSomething Please let me know if you guys see any issues with this approach, any potential problem or alternate approach for similar scenario. thanks a lot. Maddy

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  • Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

    - by Alex Kravets
    //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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  • javascript : make a new safe class constructor

    - by guilin ??
    sometimes we loss the new keyword when define new object, obj = new Clazz(); //correct obj = Clazz(); //wrong, but no syntax error, hard to debug. I want to write a function to help me create Class and make it new safe. var Class = function(constructor){ //when constructor // if not call by new return new constructor(); // else constructor(); } var MyClazz = Class(function(name){ this.name = name }, SuperClazz1, SuperClass2 ) MyClazz.extend({ show: function(){console.log(this.name)} }) obj1 = new MyClazz(); obj2 = MyClazz(); // obj1 should same as obj2 Is it possible, any exists module?

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  • C# How to Identify Caller for Template Events

    - by mikeknoop
    I have a ListBox container data bound and templatized as so: <ListBox x:Name="ListBox" ItemsSource="{Binding Source={StaticResource List}}" ItemTemplate="{StaticResource ListTemplate}"> </ListBox> Within my ListTemplate resource, I define a Grid which contains a few child elements. I have setup a click event handler on one of child elements. The event hander is not row-specific, and I need a (best practice) way of identifying which row in the ListBox the event fired upon. From my data source, I have an unique ID which corresponds to the row. I do not currently expose this ID in the data binding, though could. Ideally I would like the event handler to be able to identify the ID of the row the event was fired upon. Thank you!

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  • [GCC, linking] How to link app with static library + why this is not working

    - by user278799
    I have a problem. I wrote example code and I want to build it without the error: main.cpp.text+0x5): undefined reference to `test()' Library test1.c #include <stdlib.h> void test() { puts("Dziala"); } test1.h #ifndef TEST1_H #define TEST1_H extern void test(); #endif makefile all: gcc -c ./src/test1.c -o ./lib/test1.o ar rcs ./lib/libtest1.a ./lib/test1.o Program main.cpp #include <test1.h> int main() { test(); return 0; } makefile all: g++ -static -I../test1/include -L../test1/lib ./src/main.cpp -o ./build/MyApp -ltest1 What am I doing wrong?

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  • How to know if the argument that is passed to the function is a class, union or enum in c++?

    - by Narek
    I want to define an operator<< for all enums, to cout the value and print that it is an enum like this: code: enum AnyEnum{A,B,C}; AnyEnum enm = A; cout << enm <<endl; output: This is an enum which has a value equal to 0 I know a way of doing this with Boost library by using is_enum struct. But I don’t understand how it works. So that's why, in general, I am interested how to identify if the veriable is a class type, union type or an enum (in compile time).

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  • CSS Question - Any way to set (eg. a font-size) to a group of styles, by linking the style to anothe

    - by Joe
    .small_fonts{ font-size:10px; } .fonts_blue{ color:blue; } .fonts_red{ color:red; } .fonts_green{ color:green; } Any way to apply "small_fonts" to each of the "fonts_blue, _red, _green" w/o doing this: .fonts_blue, fonts_red, fonts_green { font-size:10px; } I am just trying to update my css to be more organized. I realised I don't need to define the font-size for each of the "small" fonts. When adding the class btw... I know you can do this: class="small_fonts fonts_blue" ~ however I'm talking about combining within the css stylesheet

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  • how do you group select_tag and text_field_tag?

    - by Eytan
    I'm trying to build a form where a user can select an existing category, or define their own. My form looks something like this... <%= f.select :category, category_options, prompt: "Select"> <%= f.text_field :category %> However, this UI is confusing. The user can select something in the select box, and type in a custom category. In this case, the final result is not obvious. Do you guys have any recommendations on how to handle this situation?

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  • C# performance of static string[] contains() (slooooow) vs. == operator

    - by Andrew White
    Hiya, Just a quick query: I had a piece of code which compared a string against a long list of values, e.g. if(str == "string1" || str = "string2" || str == "string3" || str = "string4". DoSomething(); And the interest of code clarity and maintainability I changed it to public static string[] strValues = { "String1", "String2", "String3", "String4"}; ... if(strValues.Contains(str) DoSomething(); Only to find the code execution time went from 2.5secs to 6.8secs (executed ca. 200,000 times). I certainly understand a slight performance trade off, but 300%? Anyway I could define the static strings differently to enhance performance? Cheers.

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  • MySQL Group Results by day using timestamp

    - by Webnet
    I need to take the following query and pull the total order counts and sum of the orders grouped by day. I'm storing everything using timestamps. SELECT COUNT(id) as order_count, SUM(price + shipping_price) as order_sum, DAY(FROM_UNIXTIME(created)) as day FROM `order` WHERE '.implode(' AND ', $where).' I need to group by DAY but when I do for this past weekend's sales it takes my order_count and makes it 1 instead of 3. How can I pull the above values grouped by day? NOTE: The implode is used ONLY to define the time period (WHERE created = TIMESTAMP AND <= TIMESTAMP)

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  • Reference to fnc.

    - by atch
    Hi guys, Is there a way in java to do something like this: void fnc(void Reference_to_other_func()); What I'm trying is basically I have number of places where I need to display this same text to the user and the only difference is which method is invoked after this text. So for example instead of writing: System.out.println("Hello"); f1(); //in some other place System.out.println("Hello"); f2(); //etc I would like to define one function: public void f(void Reference_to_other_func()) { System.out.println("Hello"); Reference_to_other_func();//HERE I'M INVOKING } and then instead of repeating this whole code I could write something like this: f(f1); //in some other place f(f2) //etc. Thanks for answers

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  • Android - How can I access a View object instantiated in onCreate in onResume?

    - by Chris
    In my onCreate() method, I'm instantiating an ImageButton View: public void onCreate(Bundle savedInstanceState) { Log.d(AntengoApplication.LOG_TAG, "BrowsePicture onCreate"); super.onCreate(savedInstanceState); setContentView(R.layout.layout_post); final ImageButton ib = (ImageButton) findViewById(R.id.post_image); ... In onResume, I want to be able to change the properties of the ImageButton with something like: @Override protected void onResume() { super.onResume(); ib.setImageURI(selectedImageUri); } //END onResume But onResume doesn't have access to the ib ImageButton object. If this were a variable, I'd simple make it a class variable, but Android does not allow you to define View object in the class. Any suggestions on how to do this?

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  • Casting in mixed type calculations in C?

    - by yCalleecharan
    Hi, If I define these variables: double x0, xn, h; int n; and I have this mathematical expression: h = (xn - x0)/n; Is it necessary that I cast n into double prior doing the division for maximum accuracy like in h = (xn - x0)/ (double) n; I wrote a program to check the above but both expressions give the same answers. I understand that C will promote the integer to double type as variables xn and x0 are of type double but strangely enough in a book, the second expression with casting was emphasized. Thanks a lot...

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  • Block call in Ruby on Rails

    - by Mattias
    Hi, I'm trying to clean up my code and get rid of a lot of ugly hashes. In my views I define several actions like this: @actions = { :interest => {'Show interest', link_to(..), :disabled => true}, :follow => {'Follow this case', link_to(..)} ... } As these hashes grow, the maintainability decreases. I want to convert the above format to something like: actions do item :interest, 'Show interest', link_to(..), :disabled => true item :follow, 'Follow', link_to(..) ... end How do I structure my helper methods to allow this? Preferably the 'item'-method should only be available in the 'actions' block and not in the global scope. Thanks!

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  • Flex 4: Loading XML into a Model Actionsript Class

    - by Steve
    I'm trying to create an actionscript class to serve as a data model for my Flex app. I already have a formatted XML file to read from, and when I was simply declaring the data service in my MXML app I used this code inside the declarations: I'm now trying to create a model class and can't seem to get the same functionality. I've tried importing mx.rpc.http.HTTPService but i think this is different. And using the XML class doesn't seem to allow the ability to define a source url. I'm assuming that I am able to declare a public var inside my class that will read this XML source file as I had done in the main app. If this is possible, how do I do it?

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  • Header files in C++

    - by user269037
    Hi, I am making a simulator and have written lots of files and headers. The problem is whenever I include a file I give the relative path of the particular file. For example a typical code in my application would begin like ifndef AI_H define AI_H include include "../world/world.h" include "pathPlan.h" include "skills/tryskill.h" include "../info/condition.h" include "dataStructures/destination.h" include "../params/gamePlay.h" include "../modules/controlModule.h" class ai { public: etc etc I want to avoid using the relative paths. For example I want to directly include "tryskill.h" and "destination.h" without giving the absolute paths. That way I wont need to bother if I change the location of any particular file. I am using Ubuntu 9.10. Any help would be highly appreciated.

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  • Self Modifying Python? How can I redirect all print statements within a function without touching sys.stdout?

    - by Fake Name
    I have a situation where I am attempting to port some big, complex python routines to a threaded environment. I want to be able to, on a per-call basis, redirect the output from the function's print statement somewhere else (a logging.Logger to be specific). I really don't want to modify the source for the code I am compiling, because I need to maintain backwards compatibility with other software that calls these modules (which is single threaded, and captures output by simply grabbing everything written to sys.stdout). I know the best option is to do some rewriting, but I really don't have a choice here. Edit - Alternatively, is there any way I can override the local definition of print to point to a different function? I could then define the local print = system print unless overwritten by a kwarg, and would only involve modify a few lines at the beginning of each routine.

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  • typedef to store pointers in C

    - by seriouslion
    The Size of pointer depends on the arch of the machine. So sizeof(int*)=sizeof(int) or sizeof(int*)=sizeof(long int) I want to have a custom data type which is either int or long int depending on the size of pointer. I tried to use macro #if, but the condition for macros does not allow sizeof operator. Also when using if-else, typedef is limited to the scope of if. if((sizeof(int)==sizeof(int *)){ typedef int ptrtype; } else{ typedef long int ptrtype; } //ptrtype not avialble here Is there any way to define ptrtype globally?

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