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  • A programming language for teaching data structures and algorithms with? [closed]

    - by Andreas Grech
    Possible Duplicate: Choice of programming language for learning data structures and algorithms Teachers have different opinions on what programming language they would choose to teach data structures and algorithms with. Some would prefer a lower level language such as C because it allows the student to learn more about what goes on beyond the abstractions in terms of memory allocation and deallocation and pointers and pointer arithmetic. On the other hand, others would say that they would prefer a higher level language like Java because it allows the student to learn more about the concepts of the structures and the algorithm design rather than 'waste time' and fiddle around with memory segmentation faults and all the blunders that come with languages where memory management is manual. What is your take on this issue? And also, please post any references you may know of that also discuss this argument.

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  • What's void *userData exactly?

    - by mystify
    In a C function declaration, I have seen this parameter definition: void *userData so, what exactly is that? My guess: the void says it can be anything arbitrary, or even nothing. Almost similar to id of objective-c. It just allows to pass in whatever data structure you like. The star in front of userData says, that the argument must be passed in by reference. So when using this stuff in the function body, typically it must be casted and dereferenced. So if I pass in an pointer to SomeClass instance, I would get that like this: SomeClass *myObj = (SomeClass*)userData; In the case I had nothing special to pass along, I would provide NULL as argument. Are my assumptions correct? Or did I get something wrong?

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  • Object to Network serialization - with an existing protocol

    - by cpf
    I'm writing a client for a server program written in C++. As is not unusual, all the networking protocol is in a format where packets can be easily memcopied into/out of a C++ structure (1 byte packet code, then different arrangements per packet type). I could do the same thing in C#, but is there an easier way, especially considering lots of the data is fixed-length char arrays that I want to play with as strings? Or should I just suck it up and convert types as needed? I've looked at using the ISerializable interface, but it doesnt look as low level as is required.

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  • Operator + for matrices in C++

    - by cibercitizen1
    I suppose the naive implementation of a + operator for matrices (2D for instance) in C++ would be: class Matrix { Matrix operator+ (Matrix other) const { Matrix result; // fill result with *this.data plus other.data return result; } } so we could use it like Matrix a; Matrix b; Matrix c; c = a + b; Right? But if matrices are big this is not efficient as we are doing one not-necessary copy (return result). Therefore, If we wan't to be efficient we have to forget the clean call: c = a + b; Right? What would you suggest / prefer ? Thanks.

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  • Grid view update event form javascript

    - by pranay
    I have grid control select <%--Select--% </ItemTemplate> </asp:TemplateField> </columns> <pagersettings mode="NumericFirstLast" position="Top" pagebuttoncount="5" /> <pagerstyle backcolor="Pink" /> </cc:AppEngineGridView> my code on row create protected override void OnRowCreated(GridViewRowEventArgs e) { try { if (e.Row.RowType == DataControlRowType.DataRow) { e.Row.ID = this.ID + "_" + e.Row.RowIndex; e.Row.Attributes.Add("onmouseover", "this.style.cursor='pointer';this.style.font.weight='bolder';"); e.Row.Attributes.Add("onclick", "DoNav('" + ((LinkButton)e.Row.FindControl("lbtn1")).ClientID + "');"); } } protected void grduser_RowUpdating(object sender, GridViewUpdateEventArgs e) { grdview_RowClickCommand(sender, e); } Javascript : function DoNav(id) { $("#"+id).click(); } Now my question is when i click on the row it do post back but it didnt call rowupdate event How can do this i.e using javascript to call row update command of the grid.

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  • How to read the whole istream correctly?

    - by L.Lawliet
    Here is a simple code to print all characters of a txt file on screen: #include <iostream> #include <fstream> #include <string> using namespace std; int main() { int **i; int j,k; char a; ifstream test("test.txt", ios::binary); while((a=test.get())!=-1)//if I use "while(!test.eof())" here, how to avoid the output of the last character(-1) to std::cout, or any ostream objects? { putchar(a);//also change this to putchar(test.get()); } getchar(); } As I noted in the code, if I use "test.eof()" to judge the end of test.txt, I'll always get an extra blank at the end of the output. How to avoid it?

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  • strange results with /fp:fast

    - by martinus
    We have some code that looks like this: inline int calc_something(double x) { if (x > 0.0) { // do something return 1; } else { // do something else return 0; } } Unfortunately, when using the flag /fp:fast, we get calc_something(0)==1 so we are clearly taking the wrong code path. This only happens when we use the method at multiple points in our code with different parameters, so I think there is some fishy optimization going on here from the compiler (Microsoft Visual Studio 2008, SP1). Also, the above problem goes away when we change the interface to inline int calc_something(const double& x) { But I have no idea why this fixes the strange behaviour. Can anyone explane this behaviour? If I cannot understand what's going on we will have to remove the /fp:fastswitch, but this would make our application quite a bit slower.

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  • CryptGenRandom to generate asp.net session id

    - by DoDo
    Hi! does anyone have working example of CryptGenrRandom class to generate session id (need to use in my iis module). HCRYPTPROV hCryptProv; BYTE pbData[16]; if(CryptAcquireContext( &hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { if(CryptGenRandom(hCryptProv, 8, pbData)) { std::string s(( const char *) pbData); printf(s.c_str()); } else { MyHandleError("Error during CryptGenRandom."); } } else { MyHandleError("Error during CryptAcquireContext!\n"); } i tried this code but, its not working quite well (i get it from msdn) and this example don't work for me ( http://www.codeproject.com/KB/security/plaintextsessionkey.aspx ) so if anyone know how to generate sessionid using this class plz let me know tnx anyway!

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  • parsing/matching string occurrence in C

    - by David
    I have the following string: const char *str = "\"This is just some random text\" 130 28194 \"Some other string\" \"String 3\"" I would like to get the the integer 28194 of course the integer varies, so I can't do strstr("20194"). So I was wondering what would be a good way to get that part of the string? I was thinking to use #include <regex.h> which I already have a procedure to match regexp's but not sure how the regexp in C will look like using the POSIX style notation. [:alpha:]+[:digit:] and if performance will be an issue. Or will it be better using strchr,strstr? Any ideas will be appreciate it

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  • MySQL : incrementing text id in DB

    - by BarsMonster
    I need to have text IDs in my application. For example, we have acceptable charset azAZ09, and allowed range of IDs [aaa] - [cZ9]. First generated id would be aaa, then aab, aac, aad e.t.c. How one can return ID & increment lower bound in transaction-fashion? (provided that there are hundreds of concurrent requests and all should have correct result) To lower the load I guess it's possible to define say 20 separate ranges, and return id from random range - this should reduce contention, but it's not clear how to do single operation in the first place. Also, please note that number of IDs in range might exceed 2^32. Another idea is having ranges of 64-bit integers, and converting integer-char id in software code, where it could be done asyncroniously. Any ideas?

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  • trying to make an accordion menu from a list - jquery indexhibit

    - by orionrush
    Hello - Im teaching my self javascript & jquery so this might be a bit of a low brow question or entirely too much code for anyone to wade through, but Im hoping for some feedback. I have looked around and haven't found a thread that looks like it will deals neatly with my question. Im using the cms indexhibit (cant create a new tag!) and trying to create an accordion style menu from the menu list it generates. I basically have the behaviour Im after, modifying an existing bit of work but there are quite a few foibles, which are no doubt a conflict between the .click and .toggle and a confused use if statements. I basically want to start from scratch and redo this so I can a) learn from my mistakes b) understand what's happening. Im having trouble now because I dont know where to go from here, or how to trouble shoot it. Can anyone give me a quick analysis how the the script in the head of the document work together? Also any insight into the nature of the conflicts Im seeing and what approach might take to remedy them? If you were going to start afresh what would be your approach? Here is a test to see it in action (warts and all): http://stillstatic.nfshost.com/ This script goes into the document head: <script type='text/javascript'> //im not entirely clear as to what this achieves path = 'path/to/script/'; $(document).ready(function() { setTimeout('move_up()', 1); expandingMenu(0); expandingMenu(1); expandingMenu(2); expandingMenu(3); expandingMenu(4); //etc }); </script> the generated list: <ul> <li class='section-title active_menu'>blogs</li> <li><a class="active" href='#' onclick="do_click();">3</a></li> </ul> <ul> //this menu section dose not have a label: class .section-title <li><a href='#' onclick="do_click();">1</a></li> <li><a href='#' onclick="do_click();">2</a></li> </ul> <ul> //this menu section is not the 'active menu' this is achieved by the jquery script <li class='section-title'>writing</li> <li><a href='#' onclick="do_click();">4</a></li> <li><a href='#' onclick="do_click();">5</a></li> </ul> The meat of in an external script: function expandingMenu(num) { var speed = 500; var menu_title = $("#menu ul").eq(num).children(":first"); // ie. first child be the title with the class .section-title unless the user turned it off var menu_items = $("#menu ul").eq(num).children().filter(function (index) { return index 0; }); // ie. any li NOT in position 0, below li.section-title if (menu_items.is(".active") == true) { menu_title.addClass("active_menu"); //Add a class to the active list so we can style it. } if (menu_title.is(".section-title") == true){ // this if prevents interference with users who turn off the section titling if ((menu_items.is(".active") == false) && (menu_items.is(":visible")) ) { menu_items.hide(0);// first we hide the inactive exhibits } $('li').click(function (){ if ( (menu_title.is(":visible") == true) ){ menu_items.hide(speed); } if ( (menu_items.is(":hidden") == true ) && (('')) ){// ?! without this second condition things break down. . . menu_items.show(speed); } }) menu_title.css({cursor:"pointer"}).toggle( // add click functions + pointer to menu_title function () { menu_items.show(speed);//Open it up }, function () { // this function could even be empty but without the if things get weird if (menu_items.is(".xx")) menu_items.hide(speed); //Take the menu item off of active duty! } ) } }

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  • typedef declaration syntax

    - by mt_serg
    Some days ago I looked at boost sources and found interesting typedef. There is a code from "boost\detail\none_t.hpp": namespace boost { namespace detail { struct none_helper{}; typedef int none_helper::*none_t ; } // namespace detail } // namespace boost I didn't see syntax like that earlier and can't explain the sense of that. This typedef introduces name "none_t" as pointer to int in boost::detail namespace. What the syntax is? And what difference between "typedef int none_helper::*none_t" and for example "typedef int *none_t" ?

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  • C optimization breaks algorithm

    - by Halpo
    I am programming an algorithm that contains 4 nested for loops. The problem is at at each level a pointer is updated. The innermost loop only uses 1 of the pointers. The algorithm does a complicated count. When I include a debugging statement that logs the combination of the indexes and the results of the count I get the correct answer. When the debugging statement is omitted, the count is incorrect. The program is compiled with the -O3 option on gcc. Why would this happen?

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  • Table character encoding - exception in application

    - by zgnilec
    I have a code: CREATE TABLE IF NOT EXISTS Person ( name varchar(24) ... ) CHARACTER SET utf8 COLLATE utf8_polish_ci; This works OK in my application, but I read if someone put in name field a string that contains character wchich code is greater than 127, database will use 2 bytes (or more) to store this character. So i think, i will change character set to utf16: CHARACTER SET utf16 COLLATE utf16_polish_ci; But now when I run my application, exception apears: KeyNotFoundException. It apears exactly at these instructions: MySqlCommand komenda = baza.Polaczenie.CreateCommand (); komenda.CommandText = zapytanie; MySqlDataReader dr = komenda.ExecuteReader (); // HERE, at execute reader method if (dr.Read ()) ... 1) Anyone had similar problem? 2) Any idea how to use always 2 bytes/char in database field?

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  • Why doesn't Perl threading work when I call readdir beforehand?

    - by Kevin
    Whenever I call readdir before I create a thread, I get an error that looks like this: perl(2820,0x7fff70c33ca0) malloc: * error for object 0x10082e600: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Abort trap What's strange is that it happens when I call readdir before I create a thread (i.e. readdir is not called in any concurrent code). I don't even use the results from readdir, just making the call to it seems to screw things up. When I get rid of it, things seem to work fine. Some example code is below: opendir(DIR, $someDir); my @allFiles = readdir(DIR); close(DIR); my $thread = threads-create(\&sub1); $thread-join(); sub sub1 { print "in thread\n" }

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  • How does C++ free the memory when a constructor throws an exception and a custom new is used

    - by Joshua
    I see the following constructs: new X will free the memory if X constructor throws. operator new() can be overloaded. The canonical definition of an operator new overload is void *operator new(heap h) and the corrisponding operator delete. The most common operator new overload is pacement new, which is void *operator new(void *p) { return p; } You almost always cannot call delete on the pointer given to placement new. This leads to a single question. How is memory cleaned up when X constructor throws and an overloaded new is used?

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  • SSL_CTX_set_cert_verify_callback vs. SSL_CTX_set_verify

    - by BreakPoint
    Hello, Can anyone tell me what is the difference between SSL_CTX_set_cert_verify_callback and SSL_CTX_set_verify? From OpenSSL docs: SSL_CTX_set_cert_verify_callback() sets the verification callback function for ctx. SSL objects that are created from ctx inherit the setting valid at the time when SSL_new(3) is called. and: SSL_CTX_set_verify() sets the verification flags for ctx to be mode and specifies the verify_callback function to be used. If no callback function shall be specified, the NULL pointer can be used for verify_callback. So I'm trying to understand which callback to send for each one (from client side). Thanks experts.

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  • How to build up a lookup table in microcontroller?

    - by GiGi
    Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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  • Reducing template bloat with inheritance

    - by benoitj
    Does anyone have experience reducing template code bloat using inheritance? i hesitate rewriting our containers this way: class vectorBase { public: int size(); void clear(); int m_size; void *m_rawData; //.... }; template< typename T > class vector : public vectorBase { void push_back( const T& ); //... }; I should keep maximum performance while reducing compile time I'm also wondering why stl implementations do not uses this approach Thanks for your feedbacks

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  • jQuery .submit() woes with IE8

    - by Jitesh
    I am trying to submit a delete link click via a http post to my asp.net mvc controller. While my code below works for chrome it does not work in IE8. Any pointer will be very useful. Setup:- Browser: IE8 jQuery: 1.4.1 MVC: 2.0 The delete link is:- <a title="Delete contact" href="/Contacts/Delete/<%= Model.Contact.Id %>" class="delete" rel="Are you sure you want to delete <%= Html.Encode(Model.Contact.Name) %>?">Delete</a> and the jqeury handler for the click of delete is $("a.delete").click(function() { if (confirm($(this).attr("rel"))) { var form = "<form method='POST' action='" + $(this).attr("href") + '" style='display:none;'></form>"; $(form).submit(); } return false; });

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  • How to cast a character to int in Clojure?

    - by Learning Clojure
    How to cast a character to int in Clojure? I am trying to write a rot 13 in clojure, so I need to have something to cast my char to int. I found something called (int), so I put: (int a) Get: CompilerException java.lang.RuntimeException: Unable to resolve symbol: a in this context, compiling:(NO_SOURCE_PATH:13:1) Then I put: (int 'a) Get: ClassCastException clojure.lang.Symbol cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) Then: (rot13 ''a') Get: ClassCastException clojure.lang.PersistentList cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) And: (rot13 "a") Get: ClassCastException java.lang.String cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) So what is the right way to do it? btw, I always get confused with all these clojure syntax. But I can never find any source only help me with my problem. Any suggestions? Thank you!!

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  • Trouble assigning a tr1::shared_ptr

    - by Max
    I've got a class that has a tr1::shared_ptr as a member, like so: class Foo { std::tr1::shared_ptr<TCODBsp> bsp; void Bar(); } In member function Bar, I try to assign it like this: bsp = newTCODBsp(x,y,w,h); g++ then gives me this error no match for ‘operator=’ in ‘((yarl::mapGen::MapGenerator*)this)->yarl::mapGen::MapGenerator::bsp = (operator new(40u), (<statement>, ((TCODBsp*)<anonymous>)))’ /usr/include/c++/4.4/tr1/shared_ptr.h:834: note: candidates are: std::tr1::shared_ptr<TCODBsp>& std::tr1::shared_ptr<TCODBsp>::operator=(const std::tr1::shared_ptr<TCODBsp>&) in my code, Foo is actually yarl::mapGen::MapGenerator. What am I doing wrong?

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  • File in binary form

    - by Abhi
    Dear All I want to write data into the file in binary form. I was trying using the mentioned below FILE *fp = fopen("binaryoutput.rgb888", "ab+"); for(int m=0; m<height; m++) { for (int n=0; n< width; n++) { temp = (pOutputImg+m*3+n*3); // here temp is a pointer to a unsigned char fprintf(fp,"%u",*temp); } } fclose(fp); I am able to get data which is strored at pOutputImg but not in binary form. Can anyone guide me the correct step.. Thanks in advance

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  • Casting a container of shared_ptr

    - by Jamie Cook
    Hi all, I have a method void foo(list<shared_ptr<Base>>& myList); Which I'm trying to call with a two different types of lists, one of DerivedClass1 and one of DerivedClass2 list<shared_ptr<DerivedClass1>> myList1; foo(myList1); list<shared_ptr<DerivedClass2>> myList2; foo(myList2); However this obviously generates a compiler error error: a reference of type "std::list<boost::shared_ptr<Base>, std::allocator<boost::shared_ptr<Base>>> &" (not const-qualified) cannot be initialized with a value of type "std::list<boost::shared_ptr<DerivedClass1>, std::allocator<boost::shared_ptr<DerivedClass1>>>" Is there any easy way to cast a container of shared_ptr? Of alternate containers that can accomplish this?

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