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• Why is 'using namespace std;' considered a bad practice in C++?

  - by Mana

  Okay, sorry for the simplistic question, but this has been bugging me ever since I finished high school C++ last year. I've been told by others on numerous occasions that my teacher was wrong in saying that we should have "using namespace std;" in our programs, and that std::cout and std::cin are more proper. However, they would always be vague as to why this is a bad practice. So, I'm asking now: Why is "using namespace std;" considered bad? Is it really that inefficient, or risk declaring ambiguous vars(variables that share the same name as a function in std namespace) that much? Or does this impact program performance noticeably as you get into writing larger applications? I'm sorry if this is something I should have googled to solve; I figured it would be nice to have this question on here regardless in case anyone else was wondering.

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• Post data with jQuery to ASP.net, am I doing this secure enough?

  - by Wim Haanstra

  For a website I am building, I am using jQuery to post data to Generic Handlers I created for this purpose. Because you need to be logged in, to do most post actions (like 'rate a picture'), I am currently using the following technique: User visits page Page determines if user is logged in On Page_Load the page fills a hidden field with an encrypted string, which contains several needed variables, like User ID, Picture ID (of the picture they are currently viewing), the DateTime when the page was rendered. When the user clicks a "I like this picture"-button, I do a $.ajax post to my Generic Handler, with the encrypted string and the value whether or not they liked the picture. The Generic Handler decrypts the supplied encrypted string and takes a look at the DateTime to determine if it was not too long ago When everything works out, the vote is submitted to the database. In my understanding this is a pretty secure way to handle a situation like this. But maybe I am missing a very important point here. Any advice would be very welcome.

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• Calling As function from js problem

  - by Gene

  I have a swf file that is not controlled by me. The swf expects a javascript call to set some variables after initialization. The swf is embedded using the swfobject and I'm trying to call the as function right after the embed. This appears to be too soon because I get an error. Everything else should be fine since calling the as function manually via firebug does not produce the error. So the question is how do I call the function when the embed is complete?

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• form Validation white page not showing errors

  - by Jess McKenzie

  In the example below I am wanting to do all of the 'safety' checks on the $_POST variables but it seems when I click submit I get a white page why? I am wanting it to show the errors etc Form Process: /* check if the form is submitted */ if (isset($_POST['submitButton'])) { $fullName = $_POST['fullname']; if($_SERVER['REQUEST_METHOD'] == 'POST' && !empty($fullName)) { if (!ctype_alpha(str_replace(array("'", "-"), "",$fullName))) { $errorfullName .= '<span class="errorfullName">*First name should be alpha characters only.</span>'; } if (strlen($fullName) < 3 OR strlen($fullName) > 40) { $errorfullName .= '<span class="errorfullName">*First name should be within 3-40 characters long.</span>'; } } }

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• Reference Parameters in C++: VERY basic example please.

  - by Sagistic

  I am trying to understand how to use reference parameters. There are several examples in my text, however they are too complicated for me to understand why and how to use them. Could anyone give me the MOST basic example of how/why to use one, and perhaps the difference with or without it (what would happen if you didn't attach the '&'). for example, if I've created a function: int doSomething(int& a, int& b), what would be the consequences of not putting in that '&.' I understand that reference variables are used in order to change a formal-reference, which then allows a two-way exchange of parameters. However, that is the extent of my knowledge, and a more concrete example would be of much help. Thank you.

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• Convert String containing several numbers into integers

  - by GobiasKoffi

  I realize that this question may have been asked several times in the past, but I am going to continue regardless. I have a program that is going to get a string of numbers from keyboard input. The numbers will always be in the form "66 33 9" Essentially, every number is separated with a space, and the user input will always contain a different amount of numbers. I'm aware that using 'sscanf' would work if the amount of numbers in every user-entered string was constant, but this is not the case for me. Also, because I'm new to C++, I'd prefer dealing with 'string' variables rather than arrays of chars.

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• Handling a binary operation that makes sense only for part of a hierarchy.

  - by usersmarvin_

  I have a hierarchy, which I'll simplify greatly, of implementations of interface Value. Assume that I have two implementations, NumberValue, and StringValue. There is an average operation which only makes sense for NumberValue, with the signature NumberValue average(NumberValue numberValue){ ... } At some point after creating such variables and using them in various collections, I need to average a collection which I know is only of type NumberValue, there are three possible ways of doing this I think: Very complicated generic signatures which preserve the type info in compile time (what I'm doing now, and results in hard to maintain code) Moving the operation to the Value level, and: throwing an unsupportedOperationException for StringValue, and casting for NumberValue. Casting at the point where I know for sure that I have a NumberValue, using slightly less complicated generics to insure this. Does anybody have any better ideas, or a recommendation on oop best practices?

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• Writing Strings to files in python

  - by Leif Andersen

  I'm getting the following error when trying to write a string to a file in pythion: Traceback (most recent call last): File "export_off.py", line 264, in execute save_off(self.properties.path, context) File "export_off.py", line 244, in save_off primary.write(file) File "export_off.py", line 181, in write variable.write(file) File "export_off.py", line 118, in write file.write(self.value) TypeError: must be bytes or buffer, not str I basically have a string class, which contains a string: class _off_str(object): __slots__ = 'value' def __init__(self, val=""): self.value=val def get_size(self): return SZ_SHORT def write(self,file): file.write(self.value) def __str__(self): return str(self.value) Furthermore, I'm calling that class like this: def write(self, file): for variable in self.variables: variable.write(file) I have no idea what is going on. I've seen other python programs writing strings to files, so why can't this one? Thank you very much for your help.

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• how auto submit a session based form?

  - by hd

  i have a form and want to submit it with a script. i'm going to use curl function in php to do it. but the form is not submit directly. it have 3 steps and at the end of each step it store entered value in session variables and at the final steps it insert record to database with the values are read from sessions. it is possible to do auto submit this form using curl or not? what is the best solution for it??

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• Three boolean values saved in one tinyint

  - by Casper

  Hello, probably a simple question but I seem to be suffering from programmer's block. :) I have three boolean values: A, B, and C. I would like to save the state combination as an unsigned tinyint (max 255) into a database and be able to derive the states from the saved integer. Even though there are only a limited number of combinations, I would like to avoid hard-coding each state combination to a specific value (something like if A=true and B=true has the value 1). I tried to assign values to the variables so (A=1, B=2, C=3) and then adding, but I can't differentiate between A and B being true from i.e. only C being true. I am stumped but pretty sure that it is possible. Thanks

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• PHP exec() hangs, Error 500

  - by MRX_II

  So, my plan is to make small thumbnails of URL's with PHP and IECapt. IECapt works well, a nice command line tool, gets the full sized image of specified URL in 1 to 4 seconds. But my problem is to execute it trough PHP. This is the code I've trying to get working: exec('IECapt.exe ' . escapeshellarg($URL) . ' ' . escapeshellarg($Filename)) $URL is of course the URL, and $filename is a simplified version of the URL. Sometimes I get the IECapt to snap the image(trough PHP), but it takes awfully long (30-60s), and in the end I always get a 500-error, with no error messages to tell me what's wrong. Both variables are fine, they work manually with commandline: IECapt http://google.com Google.png My server set-up is IIS7 and PHP5.2.9, if relevant. (Windows Vista, all on my personal computer, so full access.) Any ideas?

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• .htaccess redirect question

  - by russp

  I have a slight problem with .htaccess redirect. I have a dynamic site with 2 levels of variables - content="type -(alpha)" and ID="number" but this is very not seo friendly what I really would like to create is a rewrite rule that generates a "friendly" url for serach engines & users alike. Very much like WordPress does. Each ID is already unique (obviously) and on creation is creating a unique "permalink" field so for example ID=1 has a "permalink field" as "2009/10/27/page title" and ID=100 would be "2010/10/27 page title". I would like folder/wall.php?content=type&ID=number to redirect to folder/permalink.php/html/htm (don't mind a non dynamic extension) Any clues? - this is not right (I know) but it also "breaks" my css file RewriteEngine On RewriteRule wall/content/(.*)/ID/(.*)/ wall.php?content=$1&ID=$2 RewriteRule wall/content/(.*)/ID/(.*) wall.php?content=$1&ID=$2

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• How to determine the radius and center of a circle when only three noncollinear points are known?

  - by Bob

  I'm working on a C# program that deals with Oracle Spatial geometry. When circle data is stored in a geometry field only three non-collinear points are stored to represent the circle. The problem is that I need to use this data on a Google Maps web page and need the center point and radius of the circle (since my circle drawing function uses that information). Can anyone help with the math involved and translating said math to C#? I think this page may hold the answer, but I'm having a hard time following it. There are formulas for radius and center given three points, but then they define the variables as matrices and I get lost at that point. How would I solve that in code?

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• How to find the duplicate and highest value in an array

  - by Jerry

  Hello guys I have an array like this array={'a'=>'2','b'=>'5', 'c'=>'6', 'd'=>'6', 'e'=>'2'}; The array value might be different depending on the $_POST variables. My question is how to find the highest value in my array and return the index key. In my case, I need to get 'c' and 'd' and the value of 6. Not sure how to do this. Any helps would be appreciated. Thanks.

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• testing existing attribute of a @classmethod function, yields AttributeError

  - by alex

  i have a function which is a class method, and i want to test a attribute of the class which may or may not be None, but will exist always. class classA(): def __init__(self, var1, var2 = None): self.attribute1 = var1 self.attribute2 = var2 @classmethod def func(self,x): if self.attribute2 is None: do something i get the error AttributeError: class classA has no attribute 'attributeB' when i access the attribute like i showed but if on command line i can see it works, x = classA() x.attributeB is None True so the test works. if i remove the @classmethod decorator from func, the problem disapears. if i leave the @classmethod decorator, it only seems to affect variables which are supplied default values in the super-class's constructor. whats going on in the above code?

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• How can I configure a Hudson job to use a specific JDK?

  - by rewbs

  I have a number of projects running on a Hudson slave. I'd like one of them to run Ant under Java6, rather than the default (which is Java5 in my environment). In the project configuration view, I was hoping to find either: An explicit option allowing me to set a custom JDK location to use for this project. A way to set custom environment variables for this project, which would allow me to set JAVA_HOME to the JDK6 location. The would make Ant pick up and run on Java6 as desired. Is there a way to do either of the above? If one of those facilities is available, I can't see how to access it. I'm running on Hudson 1.285. I would rather avoid using an "execute shell" operation instead of the "invoke Ant" operation if possible: my slave is on z/OS and Hudson doesn't seem to create the temporary shell scripts properly on this platform (probably an encoding issue).

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• C# Comparison shorthand

  - by TheAdamGaskins

  I have this code: if (y == a && y == b && y == c && y == d ...) { ... } Is there some form of shorthand so that I can rewrite it as something like this? if(y == (a && b && c && d ...)) { ... } The functionality should be exactly the same. I'm just looking for something that looks less confusing. EDIT Sorry for not clarifying, all the variables are integers. I'm looking for a shorter way to ensure that a, b, c, d, ... all equal y.

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• C++ Memory allocation question involving vectors

  - by TheFuzz

  vector< int > vect; int *int_ptr = new int(10); vect.push_back( *int_ptr ); I under stand that every "new" needs to be followed by a "delete" at some point but does the clear() method clean this memory? What about this method of doing the same thing: vector< int > vect; int int_var = 10; vect.push_back( int_var ); From what I understand, clear() calls the variables destructors, but both vect.push_back() methods in this example push an object on the vector, not a pointer. so does the first example using an int pointer need something other than clear() to clean up memory?

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• How can I write faster JavaScript?

  - by a paid nerd

  I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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• this == null; surely not, but yes

  - by pm100

  I would have said that this will segfault but apparently not #include <stdio.h> class foo { public: bool thingy() {return this == 0;}; }; int main() { foo *f = 0; if(f->thingy()) printf("eating hat\n"); } I just expect that 0-xxx will never work. I assume that if we had to do some vtabling it would fail; obviously cannot access any member variables either edit; sorry - no question there. THe question is "are you surprised like me?" and it seems the answer is yes. even though nobody said yes. I got a) of course this will work b) of course this will never work c) it is undefined behavior; your mileage will vary

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• FETCH INTO doesn't raise an exception if the set is empty, does it?

  - by Cade Roux

  Here is some actual code I'm trying to debug: BEGIN OPEN bservice (coservice.prod_id); FETCH bservice INTO v_billing_alias_id, v_billing_service_uom_id, v_summary_remarks; CLOSE bservice; v_service_found := 1; -- An empty fetch is expected for some services. EXCEPTION WHEN OTHERS THEN v_service_found := 0; END; When the parametrized cursor bservice(prod_id) is empty, it fetches NULL into the three variables and does not throw an exception. So whoever wrote this code expecting it to throw an exception was wrong, right? The comment seems to imply that and empty fetch is expected and then it sets a flag for later handling, but I think this code cannot possibly have been tested with empty sets either. Obviously, it should use bservice%NOTFOUND or bservice%FOUND or similar.

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• Prevent Erroneous Property Assignment

  - by Gordon

  Porting android applications to iphone applications always gives me the following pattern that I accidentally create: - (void) myFunc:(id)prop { self.property = property; } Which instead should be: - (void) myFunc:(id)prop { self.property = prop; } This always causes my program to quietly break because property gets reset to its existing value rather than being set to the new value, 'prop'. I cannot name the parameter 'prop' to 'property' since the compile complains that the parameter masks the instance variables visibility. Is there a good way to avoid this situation? There are no compiler warnings. Is there a way to make xcode prevent this? I cannot see very many situations where you would set a property to the value of its underlying instance variable (maybe to trigger a KVO binding?), but I don't see myself doing that in majority of cases. I understand the above code is synthetic and should be done with @synthesize, but I am just using it as a simplified example to illustrate my point.

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• Converting c++ string to int

  - by skazhy

  Hi! I have the following data in a c++ string John Doe 01.01.1970 I need to extract the date and time from it into int variables. I tried it like this: int last_space = text_string.find_last_of(' '); int day = int(text_string.substr(last_space + 1, 2)); But I got invalid cast from type ‘std::basic_string’ to type ‘int’. When I extract the "John Doe" part in another string variable, all works fine. What's wrong? I am trying to compile it with g++ -Wall -Werror.

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• MS VC++ 6 class wizard

  - by Shane MacLaughlin

  Ok, I'm developing an application that has been in pretty much continous development over the last 16 years, from C in DOS, through various flavours of C++ and now is largely based around C++ with MFC and StingRay GUIs and various other SDKs. While I use VS 2005 for the release builds, I still use MSVC 6 for much of the GUI building, simply because ClassWizard is so much quicker in this environment than the weak equivalent tools that followed. Note that I am using ClassWizard to automatically generate code for my own user defined types (see Custom DDXs) and I like to add a lot of member variables and methods in one go. Creating them one at a time as per later versions of Visual Studio for me is a big backward step. At the same time, working with multiple IDEs is also a pain. My question is in two parts; Is there any way of getting ClassWizard to work is VS 2005 or VS 2008? Is there any drop in replacement, or alternative IDE, that provides similar levels of productivty for old C++ hacks such as myself?

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• SQL Server (TSQL) - Is it possible to EXEC statements in parallel?

  - by Investor5555

  SQL Server 2008 R2 Here is a simplified example: EXECUTE sp_executesql N'PRINT ''1st '' + convert(varchar, getdate(), 126) WAITFOR DELAY ''000:00:10''' EXECUTE sp_executesql N'PRINT ''2nd '' + convert(varchar, getdate(), 126)' The first statement will print the date and delay 10 seconds before proceeding. The second statement should print immediately. The way T-SQL works, the 2nd statement won't be evaluated until the first completes. If I copy and paste it to a new query window, it will execute immediately. The issue is that I have other, more complex things going on, with variables that need to be passed to both procedures. What I am trying to do is: Get a record Lock it for a period of time while it is locked, execute some other statements against this record and the table itself Perhaps there is a way to dynamically create a couple of jobs? Anyway, I am looking for a simple way to do this without having to manually PRINT statements and copy/paste to another session. Is there a way to EXEC without wait / in parallel?

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