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• (External) Java library for creating Tree structure ?

  - by suVasH.....

  I am planning to implement a tree structure where every node has two children and a parent along with various other node properties (and I'd want to do this in Java ) Now, the way to it probably is to create the node such that it links to other nodes ( linked list trick ), but I was wondering if there is any good external library to handle all this low level stuff. ( for eg. the ease of stl::vector vs array in C++ ). I've heard of JDots, but still since i haven't started (and haven't programmed a lot in Java), I'd rather hear out before I begin.

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• const TypedeffedIntPointer not equal to const int *

  - by dirk

  I have the following C++ code: typedef int* IntPtr; const int* cip = new int; const IntPtr ctip4 = cip; I compile this with Visual Studio 2008 and get the following error: error C2440: 'initializing' : cannot convert from 'const int *' to 'const IntPtr' Clearly my understanding of typedefs is not what is should be. The reason I'm asking, I'm storing a pointer type in a STL map. I have a function that returns a const pointer which I would like to use to search in the map (using map::find(const key_type&). Since const MyType* and const map<MyType*, somedata>::key_type is incompatible, I'm having problems. Regards Dirk

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• Implement the Combine function using templates

  - by gkid123

  any idea on how to do it for template? thanks Implement the Combine function using templates. The Combine fn applies a function of two arguments cumulatively to the items of an STL container, from begin() to end(), so as to reduce the sequence to a single value. For example, Combine(<list containing 6,3,1,9,7>, std::plus<int>()) should calculate ((((6+3)+1)+9)+7). class NotEnoughElements {}; template <typename Container, typename Function> typename Container::value_type Combine(const Container& c, Function fn) throw (NotEnoughElements) { your code goes here }

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• alternative to strdup

  - by Alexander

  I am using strdup here to copy the value of the parameter name into nm in the constructor... is there an alternative of achieving the same result without using strdup and without using the C++ STL library and using the keyword new instead? Book::Book(const char *name, int thickness, int weight):nm(NULL), thck(thickness), wght(weight){ if(name) nm = strdup(name); } class Book { private: char* nm; .......... ............ .......... ........... };

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• EHsc vc EHa (synchronous vs asynchronous exception handling)

  - by watson1180

  Could you give a bullet list of practical differences/implication? I read relevant MSDN article, but my understanding asynchronous exceptions is still a bit hazy. I am writing a test suite using Boost.Test and my compiler emits a warning that EHa should be enabled: warning C4535: calling _set_se_translator() requires /EHa The project itself uses only plain exceptions (from STL) and doesn't need /EHa switch. Do I have to recompile it with /EHa switch to make the test suite work properly? My feeling is that I need /EHa for the test suit only. Thank you and happy new year.

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• C++ visitor pattern handling templated string types?

  - by Steve the Plant

  I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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• File IO, Handling CRLF

  - by aCuria

  Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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• C/C++ enum and char * array

  - by Eric M

  Ran accross the following code in an article and didn't think it was standard C/C++ syntax for the char* array. As a test, both Visual C++ (visual studio 2005) and C++ Builder Rad XE both reject the 2nd line. Without using #defines, anyone have any tricks/tips for keeping enums and a string array sort of in sync without resorting to STL ? More of a curiosity question. enum TCOLOR { RED, GREEN, BLUE }; char *TNCOLOR[] = { [RED]="Red", [GREEN]="Green", [BLUE]="Blue" }; as an aside, the article this came from is quite old and I believe this might work under GCC but have not tested.

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• Can't inherit from auto_str without problems

  - by fret

  What I want to do is this: #include <memory> class autostr : public std::auto_ptr<char> { public: autostr(char *a) : std::auto_ptr<char>(a) {} autostr(autostr &a) : std::auto_ptr<char>(a) {} // define a bunch of string utils here... }; autostr test(char a) { return autostr(new char(a)); } void main(int args, char **arg) { autostr asd = test('b'); return 0; } (I actually have a copy of the auto_ptr class that handles arrays as well, but the same error applies to the stl one) The compile error using GCC 4.3.0 is: main.cpp:152: error: no matching function for call to `autostr::autostr(autostr)' main.cpp:147: note: candidates are: autostr::autostr(autostr&) main.cpp:146: note: autostr::autostr(char*) I don't understand why it's not matching the autostr argument as a valid parameter to autostr(autostr&).

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• Accessing typedef from the instance

  - by piotr

  As in stl containers, why can't we access a typedef inside the class from the class instance? Is there a particular insight into this? When value_type was a template parameter it could help making more general code if there wasn't the need to specify the template parameters as in vector::value_type Example: class T { public: typedef int value_type; value_type i; }; T t; T::value_type i; // ok t.value_type i; // won't work

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• Android NDK R5 and support of C++ exception

  - by plaisthos

  Hi, I am trying to use the NDK 5 full C++ gnustl: sources/cxx-stl/gnu-libstdc++/README states: This implementation fully supports C++ exceptions and RTTI. But all attempts using exceptions fail. An alternative NDK exists on http://www.crystax.net/android/ndk-r4.php. Even the hello-jni example from that site does not work. Compliation works after creating an Application.xml with APP_STL := gnustl_static But it dies the same horrific death as my own experiments. Am I am missing something or is the statement in the README just plain wrong?

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• implement string class with custom behavior

  - by truman

  In one of our class sir said that template allows one to customize behavior of class, and then he gave example of string class, that with few lines of code we can customize string class from STL, as in, we can make it to treat 'a' and 'z' same, 'b' and 'y' same, 'c' and 'x' same and so on. Similary 'A' and 'Z' same etc. "abc" == "zyx" is true; "Abc" == "zyx" is false; "Abc == "Zyx" is true; etc I was thinking of implementing such string class, but I am not able to do so. How can we implement such string class using templates?

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• Can't inherit from auto_ptr without problems

  - by fret

  What I want to do is this: #include <memory> class autostr : public std::auto_ptr<char> { public: autostr(char *a) : std::auto_ptr<char>(a) {} autostr(autostr &a) : std::auto_ptr<char>(a) {} // define a bunch of string utils here... }; autostr test(char a) { return autostr(new char(a)); } void main(int args, char **arg) { autostr asd = test('b'); return 0; } (I actually have a copy of the auto_ptr class that handles arrays as well, but the same error applies to the stl one) The compile error using GCC 4.3.0 is: main.cpp:152: error: no matching function for call to `autostr::autostr(autostr)' main.cpp:147: note: candidates are: autostr::autostr(autostr&) main.cpp:146: note: autostr::autostr(char*) I don't understand why it's not matching the autostr argument as a valid parameter to autostr(autostr&).

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• C++ containers on classes, returning pointers

  - by otneil

  Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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• Why should pop() take an argument?

  - by Stephano

  Quick background I'm a Java developer who's been playing around with C++ in my free/bored time. Preface In C++, you often see pop taking an argument by reference: void pop(Item& removed); I understand that it is nice to "fill in" the parameter with what you removed. That totally makes sense to me. This way, the person who asked to remove the top item can have a look at what was removed. However, if I were to do this in Java, I'd do something like this: Item pop() throws StackException; This way, after the pop we return either: NULL as a result, an Item, or an exception would be thrown. My C++ text book shows me the example above, but I see plenty of stack implimentations taking no arguments (stl stack for example). The Qustion How should one implement the pop function in C++? The Bonus Why?

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• Which is the best Linux C/C++ debugger (or front-end to gdb) to help teaching programming?

  - by omer.gimenez

  I teach a sort of "lite" C++ programming course to novices ("lite" meaning no pointers, no classes, just plain old C, plus references and STL string and vectors). Students have no previous experience in programming, so I believe that using an interactive debugger would help them understand program flow, variables, and recursion. The course is taught in Linux. Teaching them to use gdb is just overkill (they will not use nor understand most features). I just need something simple but easy to use: to see at which line the program is now, what is in the stack (local variables, previous calls, etc.). I look something similar to old Turbo Pascal or Turbo C++ Borland's debugger, or Visual Studio debugger. Thank you,

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• How prevent anyone from stealing my shared_ptr?

  - by Kyle

  So, I use boost::shared_ptr for all the various reference-counting benefits it provides -- reference counting for starters, obviously, but also the ability to copy, assign, and therefore store in STL Containers. The problem is, if I pass it to just one "malicious" function or object, the object can save the ptr and then I'll never be able to de-allocate it without the foreign function or object nicely relinquishing its ownership. Ultimately, I try to keep object ownership explicit. I accomplish this by having the owner keep the only shared_ptr to the object, and "guest" objects only store weak_ptrs to the object. I really don't want the "shared" part of shared_ptr, but I'm required to use shared_ptr in order to make weak_ptrs. I want to use scoped_ptr, but it's extremely limited since you can't copy it. You can't store it in a container, you can't lend out weak_ptrs from it, and you can't transfer ownership to a new manager. What's the solution?

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• CSV parser in C++

  - by User1

  All I need is a good CSV file parser for C++. At this point it can really just be a comma-delimited parser (ie don't worry about escaping new lines and commas). The main need is a line-by-line parser that will return a vector for the next line each time the method is called. I found this article which looks quite promising: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp I've never used Boost's Spirit, but am willing to try it. Is it overkill/bloated or is it fast and efficient? Does anyone have faster algorithms using STL or anything else? Thanks!

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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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• How can I switch off exception handling in MSVC?

  - by Tamara

  Does anybody know how to switch off exception handling option in MSVC? I tried to set the option 'Enable C++ exceptions' to 'NO' and I got warning: warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc I would like to switch off the exception handler, too, but I don't know how. In my application I basically need more speer than stability, therefore I chose switching off the exception handling. I do not have any try/catch blocks, but I do use STL. When I switch the option 'Enable C++ exceptions' to 'NO' is there any way how to get rid of those warnings?

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• User Defined Class as a Template Parameter

  - by isurulucky

  Hi, I' m implementing a custom STL map. I need to make sure that any data type (basic or user defined) key will work with it. I declared the Map class as a template which has two parameters for the key and the value. My question is if I need to use a string as the key type, how can I overload the < and operators for string type keys only?? In template specialization we have to specialize the whole class with the type we need as I understand it. Is there any way I can do this in a better way?? What if I add a separate Key class and use it as the template type for Key? Thank You!!

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• C++: Switching from MSVC to G++: Global Variables

  - by feed the fire

  I recently switched to Linux and wanted to compile my Visual Studio 2010 C++ source code, which uses only the STL, on G++. My Linux machine currently isn't available but I can try to tell you what is going on, first: As I try to compile my project, all global variables I use in main and which perfectly work on MSVC result in myGlobalVar is not defined in this scope errors. My project is built nearly the same as the example below: // myclass.h class myClass { // .... }; extern myClass globalInstance; // myclass.cpp #include "myclass.h" // myClass functions located here myClass globalInstance; // main.cpp #include "myclass.h" int main( ) { // Accessing globalInstance results in an error: Not defined in this scope } What am I doing wrong? Where are the differences between G++ and MSVC in terms of global variables?

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• Simple C++ container class that is thread-safe for writing

  - by conradlee

  I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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• Need recommendation for object serialization library in c++

  - by michael

  Hi, I am looking for recommendation for object serialization/deserialization library in c++? Which one are the most advanced and open-sourced? Can it handle Any class that users defined? Object hierarchy (parent and child classes)? A Tree of objects? Class A has an attribute of Class B which has an attribute of Class C? STL containers? Class A has a vector of Class B? A cyclic of objects? Class A has a pointer pointing to B which has a pointer to A? I find boost serialization library. I am not sure what is its limitation from http://www.boost.org/doc/libs/1_42_0/libs/serialization/doc/tutorial.html

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• How to get the next prefix in C++?

  - by Vicente Botet Escriba

  Given a sequence (for example a string "Xa"), I want to get the next prefix in order lexicographic (i.e "Xb"). As I don't want to reinvent the wheel, I'm wondering if there is any function in C++ STL or boost that can help to define this generic function easily? If not, do you think that this function can be useful? Notes The next of "aZ" should be "b". Even if the examples are strings, the function should work for any Sequence. The lexicographic order should be a template parameter of the function.

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