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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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  • Python: How to use code.InteractiveConsole?

    - by Rosarch
    I'm trying to use InteractiveConsole to create a new front-end for a Python interpreter. These code fragments are from me playing around with InteractiveConsole in IDLE: >>> ses = code.InteractiveConsole() >>> ses.runsource("def foo():") True >>> ses.runsource(" return 2") File "<input>", line 1 SyntaxError: 'return' outside function (<input>, line 1) False Why does it raise a syntax error? How else can I finish writing the function? Also, for something like this: >>> ses.runsource("x = 1") False >>> ses.runsource("x") 1 False How can I capture the 1 value from above? False is the return value, but 1 is written to some stream.

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  • dealing with IO vs pure code in haskell

    - by Drakosha
    I'm writing a shell script (my 1st non-example in haskell) which is supposed to list a directory, get every file size, do some string manipulation (pure code) and then rename some files. I'm not sure what i'm doing wrong, so 2 questions: How should i arrange the code in such program? I have a specific issue, i get the following error, what am i doing wrong? error: Couldn't match expected type [FilePath]' against inferred typeIO [FilePath]' In the second argument of mapM', namelyfileNames' In a stmt of a 'do' expression: files <- (mapM getFileNameAndSize fileNames) In the expression: do { fileNames <- getDirectoryContents; files <- (mapM getFileNameAndSize fileNames); sortBy cmpFilesBySize files } code: getFileNameAndSize fname = do (fname, (withFile fname ReadMode hFileSize)) getFilesWithSizes = do fileNames <- getDirectoryContents files <- (mapM getFileNameAndSize fileNames) sortBy cmpFilesBySize files

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  • finding the numbers in a given range?

    - by Jamis
    Hi Friends, kindly tel me the concept to write a perl program behind this ? 167 GATCAAAATACTTGCTGGA 185 192 TAGTAGATAGATAGATAGTAGTAG 228 in a fileA i ve a range from 167 to 185 as given as above and also 192 to 228 in another fileB i ve set of numbers 2 3 4 5 6 7 8 168 169 179 185 193 1000 now from the above set of numbers in file B, i need to find out which are the numbers present between the range of 167 to 185 and print those numbers in the output. so, output will be 168,169,179,185, 193 what will be the concept behind writing this program?

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  • Likelihood of IOError during print vs. write

    - by jkasnicki
    I recently encountered an IOError writing to a file on NFS. There wasn't a disk space or permission issue, so I assume this was just a network hiccup. The obvious solution is to wrap the write in a try-except, but I was curious whether the implementation of print and write in Python make either of the following more or less likely to raise IOError: f_print = open('print.txt', 'w') print >>f_print, 'test_print' f_print.close() vs. f_write = open('write.txt', 'w') f_write.write('test_write\n') f_write.close() (If it matters, specifically in Python 2.4 on Linux).

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  • How to write a xpath to match all elements except a particular element

    - by Unmesh Kondolikar
    I am writing an XSL transformation. I want to write a template which matches all the child elements of the document except one particular node. My xml looks like this - <Document> <NodeA><\NodeA> <NodeB><\NodeB> <ServiceNode><\ServiceNode> <NodeX><\NodeX> </Document> I want to write a template that matches all nodes except ServiceNode i.e. NodeA to NodeX. How to write this Xpath to get - <xsl:template match="ALL Nodex Except ServiceNode">

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  • What happens when I MPI_Send to a process that has finished?

    - by nieldw
    What happens when I MPI_Send to a process that has finished? I am learning MPI, and writing a small sugar distribution-simulation in C. When the factories stop producing, those processes end. When warehouses run empty, they end. Can I somehow tell if the shop's order to a warehouse did not succeed(because the warehouse process has ended) by looking at the return value of MPI_Send? The documentation doesn't mention a specific error code for this situation, but that no error is returned for success. Can I do: if (MPI_Send(...)) { ... /* destination has ended */ ... } And disregard the error code? Thanks

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  • How to create a MySQL query for time based elements with a 'safe window'?

    - by pj4533
    I am no SQL expert, far from it. I am writing a Rails application, and I am new at that as well. I come from a desktop programming background. My application has a table of data, one of the columns is the time at which the data was logged. I want to create a query with a 'safe window' around EACH row. By that I mean, it returns the first row, then for X minutes (based on the timelogged column) it won't return any data, once X minutes is up, it will return the next row. For example: ID | TimeLogged 1 | 3/5/2010 12:01:01 2 | 3/5/2010 12:01:50 3 | 3/5/2010 12:02:03 4 | 3/5/2010 12:10:30 5 | 3/5/2010 01:30:03 6 | 3/5/2010 01:31:05 With a 'safe window' of 5 minutes I want to create a query to return: 1 | 3/5/2010 12:01:01 4 | 3/5/2010 12:10:30 5 | 3/5/2010 01:30:03 (It skipped the 12:01:50 and 12:02:03 items because they occurred within 5 minutes of the first item.) Another example, with a 'safe window' of 15 minutes I want to return: 1 | 3/5/2010 12:01:01 5 | 3/5/2010 01:30:03 Perhaps I have to just return all data and parse it myself?

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  • How to trigger Mouse-Over on iPhone?

    - by Andrew
    This might seem like a really dumb question, but I am writing an application and I have come across where my mouse-over, mouse-click and mouse-hover need different events bound to them. Now on Internet Explorer, Firefox, and Safari. It all works as expected. However, on my iPhone the actions will not trigger. Now my question is are their any specific ways I can have the Mouse-Over essentially be fired when I hold my finger down and trigger an event? An example where this doesn't work is right on this website when you hover over a comment it is supposed to display the +1 or flag icon. I am using jquery.

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  • networkstream always empty!

    - by ALEX
    hey I'm writing on an Server-Client program but when my client sends something, it never reaches my server! I'm sending like this: public void Send(string s) { char[] chars = s.ToCharArray(); byte[] bytes = chars.CharToByte(); nstream.Write(bytes, 0, bytes.Length); nstream.Flush(); } and Receiving in a background thread like this void CheckIncoming(object dd) { RecievedDelegate d = (RecievedDelegate)dd; try { while (true) { List<byte> bytelist = new List<byte>(); System.Threading.Thread.Sleep(1000); int ssss; ssss = nstream.ReadByte(); if (ssss > 1) { System.Diagnostics.Debugger.Break(); } if (bytelist.Count != 0) { d.Invoke(bytelist.ToArray()); } } } catch (Exception exp) { MSGBOX("ERROR:\n" + exp.Message); } } the ssss int is never 1 whats happening here???

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  • closing sockets on linux and windows

    - by robUK
    Hello, gcc 4.4.4 c89 Visual Studio VC++ 2008 I am writing a cross platform client server application. It will run on both linux and windows. However, I am just wondering what I have done for closing the sockets is correct. I close the file descriptor. However, if there is a problem with closing it. What is the best way to handle this. Maybe some data is still being sent or received? Many thanks for any advice, if(close(sockfd) == -1) { #if defined ( _WIN32 ) fprintf(stderr, "[ %d ] [ %s ] [ %s ] [ %d ]\n", WSAGetLastError(), strerror(errno), __func__, __LINE__); #elif( __linux__ ) fprintf(stderr, "[ %s ] [ %s ] [ %d ]\n", strerror(errno), __func__, __LINE__); #endif return CS_FAILURE; }

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  • Is 'bool' a basic datatype in C++ ?

    - by Naveen
    I got this doubt while writing some code. Is 'bool' a basic datatype defined in the C++ standard or is it some sort of extension provided by the compiler ? I got this doubt because Win32 has 'BOOL' which is nothing but a typedef of long. Also what happens if I do something like this: int i = true; Is it "always" guaranteed that variable i will have value 1 or is it again depends on the compiler I am using ? Further for some Win32 APIs which accept BOOL as the parameter what happens if I pass bool variable?

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  • How do you get 100% code coverage with guards in Haskell?

    - by dan_waterworth
    I'm trying to get (and prove) 100% test coverage for some code I'm writing in Haskell using HPC. However if I write something like this: fac n | n > 0 = n * (fac (n - 1)) | otherwise = 1 Then the second expression of the guard statement has always True tagged to it. What is the easiest way to overcome this in the general case? edit: Just to clarify. This code: fac n = if n > 0 then n * (fac (n - 1)) else 1 Works fine with HPC, (running it gives 100% code coverage). I'm basically suffering from this problem: http://hackage.haskell.org/trac/ghc/ticket/3175

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  • Is it a header file or library? in a makefile

    - by gccinac
    I already know the differences between a header file and a library. However, when I'm writing my makefile, I have some difficulties on deciding if I should put something as a dependency of the file or just at the linking rule. For example: I have 2 simple files: main.c: #include <stdio.h> main(){ printf("this is the sine or 90"); sinus(90); } and func.c: #include <math.h> sinus(int num){ return sin(num); } and my makefile is: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c main.o: main.c Well, my question is why this makefile works and this one doesn't: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c math.h main.o: main.c

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  • Server Side code Pushing Data to client Browser while current thread is busy Comet (programming)

    - by h_power11
    Hello Friends, I am writing one simple web page with bunch of textboxes and a button control. Now when user finished editing the values on this text boxes user has to click the button and this button invoke heavily process intensive algorithm on server side code based on the data received from client (Textboxes) And it could some time takes up to 30 to 45 minutes to complete the whole operation so the current thread is still inside the button click event handler function. That background task only provides one event, and the web page subscribes to it to get some text data after each stage of processing I was wandering if there is any way I can keep user up-to-date with what is the current progress on that background task. I have div element to print the current status information So I am looking for some sort of reverse mechanism then "get" and "post". I have read some articles on the Comet (programming) but I can't find any easy or definitive answer Thanks in advance

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  • PHP: How to begin testing large, existing codebase, and test for regression on production site?

    - by anonymous coward
    I'm in charge of at least one large body of existing PHP code, that desperately needs tests, and as well I need some method of checking the production site for errors. I've been working with PHP for many years, but am unfortunately new to testing. (Sorry!). While writing tests for code that has predictable outcomes seems easy enough, I'm having trouble wrapping my head around just how I can test the live site, to ensure proper output. I know that in a test environment, I could set up the database in a known state... but are there proper methods or techniques for testing a live site? Where should I begin? [I am aware of PHPUnit and SimpleTest, but haven't chosen one over the other yet]

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  • Problem in removing hardcoded values using temp table...

    - by Shahsra
    Hi All, First of all Wish u all Happy New Year. I have a problem in writing query. While executing my query I am getting an error. Query: select case when S.R1 = '6' then 5 when S.R1 = '7' then 6 when S.R1 = '8' then 7 when S.R1 = '9' then 8 when S.R1 ='10' then 9 else S.R1 end as Q FROM [HelpService].[dbo].[help] s ----------------------------------------------- SELECT [Source], [Score] INTO #Temp_Q FROM [HelpDesk].[dbo].[Survey] WHERE [data_Source Name] = 'Text Data' ----------------------------------------------- select CONVERT(REAL, a.[Dell Score]) as Q FROM [HelpService].[dbo].[help] s LEFT OUTER JOIN #CE_Temp_Q a on s.[R1] = a.[Source] ERROR Msg 8114, Level 16, State 5, Line 1 Error converting data type varchar to real. What I am asked to do is I need to remove the hard coded values and need to write queries with a temp table. Thanks in Advance, Shashra

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  • In web project can we write core services layer without knowledge of UI ?

    - by Silent Warrior
    I am working on web project. We are using flex as UI layer. My question is often we are writing core service layer separately from web/UI layer so we can reuse same services for different UI layer/technology. So practically is it possible to reuse same core layer services without any changes/addition in API with different kind of UI technologies/layers. For e.g. same core service layer with UI technology which supports synchronized request response (e.g. jsp etc.) and non synchronize or event driven UI technology (e.g Ajax, Flex, GWT etc.) or with multiple devices like (computers, mobiles, pdas etc.). Personally I feel its very tough to write core service layer without any knowledge of UI. Looking for thoughts from other people.

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  • I have some basic questions setting up a PHP daemon

    - by mike
    I will be writing my first daemon in php and I have a couple really basic questions that I need help with. 1) What packages need to be installed on my linux server and Does anything in PHP need to be enabled? So far I have gotten this - http://pear.php.net/package/System_Daemon/download 2) Where on server do I save my daemon files? 3) I have a number of files that need to be included within the daemon that contain classes and functions for gathering emails and attachments through IMAP. All of these files are currently in my web public directory, how do I include these files within my daemon? I think that is everything I need to get started. Thanks so much!

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  • Language restrictions on iPhone lifted?

    - by John Smith
    Apparently Apple has changed some term in the agreement again. From http://www.appleoutsider.com/2010/06/10/hello-lua/ section 3.3.2 is now Unless otherwise approved by Apple in writing, no interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). Notwithstanding the foregoing, with Apple’s prior written consent, an Application may use embedded interpreted code in a limited way if such use is solely for providing minor features or functionality that are consistent with the intended and advertised purpose of the Application. instead of the original No interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). I am more interested in embedding Lua, but other people have other embeddings they want to make. I am wondering how you ask for permission, and what they mean by the terms "minor features" and "consistent" and how will Apple interpret this section? It seems to have enough loopholes to drive a real firetruck through.

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  • TDD, Unit Test and architectural changes

    - by Leandro
    I'm writing an RPC middleware in C++. I have a class named RPCClientProxy that contains a socket client inside: class RPCClientProxy { ... private: Socket* pSocket; ... } The constructor: RPCClientProxy::RPCClientProxy(host, port) { pSocket = new Socket(host, port); } As you can see, I don't need to tell the user that I have a socket inside. Although, to make unit tests for my proxies it would be necessary to create mocks for sockets and pass them to the proxies, and to do so I must use a setter or pass a factory to the sockets in the proxies's constructors. My question: According to TDD, is it acceptable to do it ONLY because the tests? As you can see, these changes would change the way the library is used by a programmer.

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  • How to access constant defined in child class?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • C++ performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • travesersing the dom with inexact parameters

    - by rashcroft23
    Hi, I want to grab the image src on a product page in a e commerce website. I'm writing this as a bookmarklet, so I'd like the code to work universally as possible. I've noticed that there are only two reoccurring factors in the product image tag among top e-commerce websites (amazon, bestbuy ect.): border=0 and 180<width&height<400. So how could I write a selector that would give me the srcof the first img element on the page with no border and width & height between 180 and 400 px? Or is there a better way of doing this? P.S. since I'm trying to keep the bookmarklet as light as possible, I don't want to use any libraries (jquery, yui etc)

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  • How much RAM used by Python dict or list?

    - by Who8MyLunch
    My problem: I am writing a simple Python tool to help me visualize my data as a function of many parameters. Each change in parameters involves a non-trivial amount of time, so I would like to cache each step's resulting imagery and supporting data in a dictionary. But then I worry that this dictionary could grow too large over time. Most of my data is in the form of Numpy arrays. My question: How would one go about computing the total number of bytes used by a Python dictionary. The dictionary itself may contain lists and other dictionaries, each of which contain data stored in Numpy arrays. Ideas?

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