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  • C++ STL: Trouble with string iterators

    - by Rosarch
    I'm making a simple command line Hangman game. void Hangman::printStatus() { cout << "Lives remaining: " << livesRemaining << endl; cout << getFormattedAnswer() << endl; } string Hangman::getFormattedAnswer() { return getFormattedAnswerFrom(correctAnswer.begin(), correctAnswer.end()); } string Hangman::getFormattedAnswerFrom(string::const_iterator begin, string::const_iterator end) { return begin == end? "" : displayChar(*begin) + getFormattedAnswerFrom(++begin, end); } char Hangman::displayChar(const char c) { return c; } (Eventually, I'll change this so displayChar() displays a - or a character if the user has guessed it, but for simplicity now I'm just returning everything.) When I build and run this from VS 2010, I get a popup box: Debug Assertion Failed! xstring Line: 78 Expression: string iterator not dereferenceable What am I doing wrong?

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  • Relationship problem?

    - by dilip
    I have four tables Tag=id,tag_name Image=Id,Image_name TagImage=Id,tag_id,Image_id ImageStudent=id,Image_id,student_id And I want to find a record using student id and tag name. What relationship do I use?

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  • Java: ListA.addAll(ListB) fires NullPointerException?

    - by HH
    The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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  • Python os.path.walk() method

    - by Aaron Moodie
    I'm currently using the walk method in a uni assignment. It's all working fine, but I was hoping that someone could explain something to me. in the example below, what is the a parameter used for on the myvisit method? >>> from os.path import walk >>> def myvisit(a, dir, files): ... print dir,": %d files"%len(files) >>> walk('/etc', myvisit, None) /etc : 193 files /etc/default : 12 files /etc/cron.d : 6 files /etc/rc.d : 6 files /etc/rc.d/rc0.d : 18 files /etc/rc.d/rc1.d : 27 files /etc/rc.d/rc2.d : 42 files /etc/rc.d/rc3.d : 17 files /etc/rc.d/rcS.d : 13 files

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  • What is the most underused or underappreciated design pattern?

    - by Rob Packwood
    I have been reading a lot on design patterns lately and some of them can make our lives much easier and some of them seem to just complicate things (at least to me they do). I am curious to know what design patterns everyone sees as underunsed or underappreciated. Some patterns are simple and many people do not even realize they are using a pattern (decorator probably being the most used, without realized). My goal from this is to give us pattern-newbies some appreciation for some of the more complex or unknown patterns and why we should use them.

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  • linked list problem (with insert)

    - by JohnWong
    The problem appears with the insert function that I wrote. 3 conditions must work, I tested b/w 1 and 2, b/w 2 and 3 and as last element, they worked. But b/w 3 and 4, it did not work. It only display up to the new added record, and did not show the fourth element. Efficiency is not my concern here (not yet). Please guide me through this debug process. Thank you very much. #include<iostream> #include<string> using namespace std; struct List // we create a structure called List { string name; string tele; List *nextAddr; }; void populate(List *); void display(List *); void insert(List *); int main() { const int MAXINPUT = 3; char ans; List * data, * current, * point; // create two pointers data = new List; current = data; for (int i = 0; i < (MAXINPUT - 1); i++) { populate(current); current->nextAddr = new List; current = current->nextAddr; } // last record we want to do it sepeartely populate(current); current->nextAddr = NULL; cout << "The current list consists of the following data records: " << endl; display(data); // now ask whether user wants to insert new record or not cout << "Do you want to add a new record (Y/N)?"; cin >> ans; if (ans == 'Y' || ans == 'y') { /* To insert b/w first and second, use point as parameter between second and third uses point->nextAddr between third and fourth uses point->nextAddr->nextAddr and insert as last element, uses current instead */ point = data; insert(()); display(data); } return 0; } void populate(List *data) { cout << "Enter a name: "; cin >> data->name; cout << "Enter a phone number: "; cin >> data->tele; return; } void display(List *content) { while (content != NULL) { cout << content->name << " " << content->tele; content = content->nextAddr; cout << endl; // we skip to next line } return; } void insert(List *last) { List * temp = last->nextAddr; //save the next address to temp last->nextAddr = new List; // now modify the address pointed to new allocation last = last->nextAddr; populate(last); last->nextAddr = temp; // now link all three together, eg 1-NEW-2 return; }

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  • Delete an (exact) element from an array in php

    - by Holian
    Hi Masters! For example i have an array like this: $test= array("0" => "412", "1" => "2"); I would like to delete the element if its = 2 $delete=2; for($j=0;$j<$dbj;$j++) { if (in_array($delete, $test)) { unset($test[$j]); } } print_r($test); But with this, unfortunatelly the array will empty... How can i delete an exact element from the array? Thank you

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  • Understanding PHP's way of reading if statements

    - by Masi
    How does PHP read if statements? I have the following if statements in this order if ( $number_of_figures_in_email < 6) { -- cut: gives false } if($number_of_emails > 0) { -- cut: gives false } if ( $number_of_emails == 0) { -- cut: gives true } The code behaves randomly. It sometimes goes to the third if clause and gives me a success, while sometimes to the one of the first two if clauses when the input variables are constant. This suggests me that I cannot code only with if statements.

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  • Separating a group of functions into an includable file in C?

    - by zebra
    I know this is common in most languages, and maybe in C, as well. Can C handle separating several functions out to a separate file and having them be included? The functions will rely on other include files, as well. I want the code to retain all functionality, but the code will be reused in several C scripts, and if I change it once I do not wish to have to go through every script and change it there, too.

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  • Same script, working on a site, not working on the other!

    - by Tioneb
    Hello, First of all I apologize in advance for this question, a bit off the rang of stackoverflow, but I've spend a day trying to solve that issue and I'm totally stuck. The issue: The search function of my script (php) works perfectly fine on one host but not on the other. If you search something here : edu-cafe.com, you'll get a result, just as it should be. However, try a search on this site, hosted somewhere else : code-reduc.com, exact same script, files and datable, and it just hang. I've asked both the host and the original programmer of the script to look at the issue but they can't seem to find an answer... Obviously the cause of my troubles comes from the Host, but I can't find the issue Any bit of help would be hugely appreciated! PS: part of the script here: http://codepaste.net/fuymqn Thanks!

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  • How can I add file locations to a database after they are uploaded using a Perl CGI script?

    - by Paul K
    I have a CGI program I have written using Perl. One of its functions is to upload pics to the server. All of it is working well, including adding all kinds of info to a MySQL db. My question is: How can I get the uploaded pic files location and names added to the db? I would rather that instead of changing the script to actually upload the pics to the db. I have heard horror stories of uploading binary files to databases. Since I am new to all of this, I am at a loss. Have tried doing some research and web searches for 3 weeks now with no luck. Any suggestions or answers would be greatly appreciated. I would really hate to have to manually add all the locations/names to the db. I am using: a Perl CGI script, MySQL db, Linux server and the files are being uploaded to the server. I AM NOT looking to add the actual files to the db. Just their location(s).

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  • Haskell "Source reduction"

    - by Martin
    I'm revising for an upcoming Haskell exam and I don't understand one of the questions on a past paper. Google turns up nothing useful fst(x, y) = x square i = i * i i) Source reduce, using Haskells lazy evaluation, the expression: fst(square(3+4), square 8) ii) Source reduce, using strict evaluation, the same expression iii) State one advantage of lazy evaluation and one advantage of strict evaluation

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  • C++: Trouble with dependent types in templates

    - by Rosarch
    I'm having trouble with templates and dependent types: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> set<result_t> findAll_if(typename set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred) // warning C4346 { set<result_t> result; return findAll_if_rec(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> set<result_t> findAll_if_rec(set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred, set<result_t> result) { typename set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.add(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } Compiler complaints, from the location noted above: warning C4346: 'std::set<result_t>::iterator' : dependent name is not a type. prefix with 'typename' to indicate a type error C2061: syntax error : identifier 'iterator' What am I doing wrong?

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  • F# - Function with no arguments?

    - by Rubys
    When thinking in a functional mindset, given that functions are supposed to be pure, one can conclude any function with no arguments is basically just a value. However, reallity gets in the way, and with different inputs, I might not need a certain function, and if that function is computationally expensive, I'd like to not evaluate it if it's not needed. I found a workaround, using let func _ = ... and calling it with func 1 or whatever, but that feels very non-idiomatic and confusing to the reader. This boils down to one question: In F#, Is there a proper way to declare a function with zero arguments, without having it evaluated on declaration?

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  • Clarification of a some code

    - by Legend
    I have come across a website that appears to use Ajax but does not include any js file except one file called ajax.js which has the following: function run(c, f, b, a, d) { var e = null; if (b && f) { document.getElementById(b).innerHTML = f } if (window.XMLHttpRequest) { e = new XMLHttpRequest() } else { if (window.ActiveXObject) { e = new ActiveXObject(Microsoft.XMLHTTP) } } e.onreadystatechange = function () { if (e.readyState == 4) { if (e.status == 200 || e.statusText == "OK") { if (b) { document.getElementById(b).innerHTML = e.responseText } if (a) { setTimeout(a, 0) } } else { console.log("AJAX Error: " + e.status + " | " + e.statusText); if (b && d != 1) { document.getElementById(b).innerHTML = "AJAX Error. Please try refreshing." } } } }; e.open("GET", c, true); e.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); e.send(null) } Like you might have guessed, the way it issues queries inside the page with queries like this: run('page.php',loadingText,'ajax-test', 'LoadSamples()'); I must admit that this is the first time I've seen a page from which I could not figure how things are being done. I have a few questions: Is this Server-Side Ajax or something similar? If not, can someone clarify what exactly is this? Why does one use this? Is it for hiding the design details? (which are otherwise revealed in plain text by javascript) How difficult would it be to convert my existing application into this design pattern? (maybe a subjective question but any short suggestion will do) Any suggestions?

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  • Creating a series of vectors from a vector

    - by bluetongue
    I have a simple two vector dataframe (length=30) that looks something like this: > mDF Param1 w.IL.L 1 AuZgFw 0.5 2 AuZfFw 2 3 AuZgVw 74.3 4 AuZfVw 20.52 5 AuTgIL 80.9 6 AuTfIL 193.3 7 AuCgFL 0.2 8 ... I'd like to use each of the rows to form 30 single value numeric vectors with the name of the vector taken from mDF$Param1, so that: > AuZgFw [1] 0.5 etc I've tried melting and casting, but I suspect there may be an easier way?? Thanks in advance BT

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