I'm making my first steps in STL, and I have a few question:
Is there a way to get an iterator to the i'th element in the collection (set or list), instead of just to the end or the begin?
And another question: Let's say I have an iterator, pointing to some element in my collection, and I use erase() (which takes as parameter an iterator that points to the soon-to-be erased element), what happens to that iterator? will it now point to NULL?
Why this code works Elenco e1; e1.add(Persona("a","b")); e1.add(Persona("c","d")); e1.add(Persona("e","f")); e1.add(Persona("e","f")); e1.remove(2); //list of 4 elements
but this not work? Elenco e1; e1.add(Persona("a","b")); e1.add(Persona("c","d")); e1.add(Persona("e","f")); e1.remove(2); //list of 3 elements
This is remove method: Persona Elenco:: remove(int pos){ list<Persona> ::iterator iter=l.begin(); for(int i=0 ;i<pos;i++){ iter++; } return *(l.erase(iter)); //erase ritorna un iterator }
Here's a few parts of a program I'm working at. It does compile, and it does work as expected. Anyway Eclipse Kepler marks one line as a bug with the remark Field 'befehl' could not be resolved. The bug sign didn't show up when both classes were in one file.
ScriptInterpreter maintains and processes a vector of Objects, initialised with example data. An iterator of the vector keeps track of the current position while various methods process the data. I've copied the relevant lines only.
I can live with a few wrongly bug-marked lines in Eclipse. What I don't want is any hidden errors that express at some time later.
Is there anything wrong with the code? Anything that's not recommended and compiles anyway? Is anything c++11-specific about the questionable line?
AtomicCommand.h class AtomicCommand { public: int befehl;
[Code] .....
Note that line 9 has a bug sign, too. Eclipse doesn't recognise all my c++11 code.
I can't seem to make the STL iterator class work how I need it to.I am implementing a multi list graph and I need to iterate through my STL list of Vertex pointer objects. I keep getting the error:
Error 1 error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::_List_iterator<_Mylist>' (or there is no acceptable conversion) and the same for != for my terminating condition.
template <typename V, typename E> void Graph<V, E>::InsertEdge(V from, V to, E edge) { list<Vertex<V>*>::iterator iter; for(iter = m_Vertices.begin(); iter != m_Vertices.end(); ++iter)
I just figured out that some std functions (for example: copy) need the resource and target objects have iterators to work. Otherwise, the compiler rejects. In case of two arrays, declared as:
myA[0] is like a pointer, myB.begin() an iterator, if I do not make any mistake. So, what is exactly the difference between the pointer and the iterator here? They all give the access to elements.
If I need the target of copy to be an array like myA which cannot give an iterator, is there a way to make the command "copy" work for it?
I want to get the iterator position after to use find if:
std::list<Texture*>::iterator result = find_if( texturelist.begin(), texturelist.end(), std::bind2nd<CompareTEX>(CompareTEX(),n_tex)); if (result != texturelist.end()) { return // position result }
I am receiving the error: Vector Iterator not incrementable. However, when erasing I'm already re-setting 'it' and pre-incrementing at the end of the while-clause.what's wrong?
We were given a task to use lists and iterators. We were supposed to make them from scratch. I'm done with that. The problems that I'm having are as following:
1. I'm not able to access the list made of Course datatype which is present in each Student instance. Does this mean I need to make an iterator for that course list inside the student class?
2. Similarly since I don't have direct access to The course list so I added the course into the Student list through the student objects not through the iterator. How can I do it through the iterator?
3. Printing of a particular student and his courses is not happening as my iterator made for student only prints out the students, not the courses present in their courselist. How to do that?
Here's the code
#include <iostream> #include <string> using namespace std; const int ILLEGAL_SIZE = 1; const int OUT_OF_MEMORY = 2; const int NO_SPACE = 3; const int ILLEGAL_INDEX = 4;
I have created a multimap for my road points. The key refers to the road number and the values are vec3 points that make up the road.
I am trying to iterate through the values of each key point and create a road segment at each point on the road (except the last), adjust the values to be on the road points and then store them in a std::vector.
The RoadSegment constructor creates 6 vec3 points and pushes them onto a std::vector.
I have a segmentation fault in the line marked in bold [for(mapIt = it.first; mapIt != it.second; ++mapIt)]
When i take out the lines creating the new objects and pushing them onto the std::vector it works fine.
std::vector<glm::vec3>::iterator SegIt; for(int i = 0; i < m_genRoads->getKeyValueData().size(); i++) { int numberDesired = m_genRoads->getMultimapData().count(i) - 1;
I defined the following function to find out the iterator of a certain value in the vector. I defined it as such so if the value exist in the vector then return a iterator of it, if not then return a pointer pointing to nonsense.:
I'm working on a program where I have a vector full of <myClassType> structs.
I'm trying to insert items into a vector, searching first through the vector to make sure the value isn't already in the vector before inserting it. The "find" function isn't working properly.
I keep getting C2678 "binary '==': no operator found which takes a left-hand operand of type "myClassType" or there is no conversion errors in Visual Studio 2010.
I know it's something having to do with the find function and my iterators, but I can't, for the life of me, figure out what it is.
I've tried switching to const_iterators, but I get the same error message.
However, I got this error in the 'for' line: "error: expected ‘;’ before ‘it’" (and then errors that it is not declared, etc). I'm sure that there is no missing ; in other functions. If you try to write a random line before that you get no error there for example, always in the for.
It is there something that you need to do with iterators when you declare generic datatypes?
Using GDB, I am able to find out that it crashes at the "++iter" as the .h file indicate it was a "++" operation for the iterator. Tracing up the stack frame it indicate it crash during the copy constructor of some "__rb_tree_node". I did some Googling and it seems that is some Red-Black tree implementation for the map. Honestly I do not quite understand the Red-Black tree and I believe STL map is a very very well tested container, so the problem must lie in my code so that I can look out for it.
In order to parse mathematical expressions I am trying regular expressions and a recursive algorithm, but I have a problem with the four basic operations: +, -, *, /.
Trying to analyze a string like "a+(b+c)", if I use the pattern for a sum "(.+)+(.+)" the program matches it recognizing as subpatterns: "a+(b" and "c". How could I achieve the program to try also the other possibility?
I think that it would be great something like an regex_iterator which worked with regex_match instead of regex_search. I mean, an iterator that iterates over all the possible ways to match a given regular expression and a given string. This way I could loop through all these possibilities until the two subpatterns produced were correct mathematical expressions.
what i do with this is to stack fragments of data of type char* coming from a socket in buffer to a vector that acts as buffer, I do this since I transfer big chunks of data and the data gets fragmented by the nature of the sockets, I stack the data once its complete I retrieve the final result from the vector.
this code worked flawlessly for long time but now Im trying to port and compiler throws this error, whats the new way to assign a char array pointer to a iterator so i can stack it in the vector.
My assignment is to write a system for managing a radio station. The code is composed of four classes:
Song: each song has a name, a composer and a singer, and has a few segments: INTRO,VERSE,CHORUS,TRANSITION, while each represents a different length string of chars. Playlist: a multiset of songs, and a pointer to a RadioStatistics instance (see below). RadioStation: a set of Songs (will represent the station database), and a list of Playlists, each playlist holds a few songs from the database. RadioStatistics: can only be instantiate once, this object gather statistics; it has two maps: one that counts how many times a song was played, and second that counts how many times each singer was played. (the key is the song/singer name, and the value is the counter).
The RadioStation has a constant that defines a limit to how many times a song is allowed to be played. whenever a song reaches this limit (meaning, it was played too much), the program needs to skip to the next song in the database.
so, I run this test from main, and the program crashes (or more accuratly get stuck, since the console stays open and the program keeps working until I stop it).
I made a few changes and run the debugger a few times, and was able to focus on the problem.
I ran a step by step debugger, and found out the problem lays with line 90 in RadioManager.cpp, when the while loop runs its fourth iteration. It crashes when it tries to dereference the iterator, while it points to the fourth playlist in the list.
And here's some more weird stuff: when I comment out line 73 in main.cpp - it works perfectly fine! (line 73 in particular! commenting out any other line in main.cpp didn't worked around the bug!)
I have a templated container that defines a forward iterator.
Calling std::distance on these iterators will generate code that will count the number of iterations it takes to get from the first parameter to the second, by repetitively incrementing.
Internally, the iterators can easily find the distance by a simple subtraction.
What I want to do is overload std::distance for these iterators so that it will take advantage of the simple calculation rather than repetitive increments.
The simple solution of course would be to make the iterators random access, but this would require that they support functionality that is not 'logical' for the container. Access to the container only makes logical sense when iterating one item at a time in the forward direction.
Code: #include <iterator> template <typename T> class Container { public: class iterator : public std::iterator<std::forward_iterator_tag, T> {
I'm trying to use the given Iterators to overload my = operator to print my list to screen. I keep getting Link2019 error though and have narrowed the problem down to my print operator. I'm wondering if it has anything to do with the fact that my operator is in private part of class? I'm new to this concept.
Code: #include "List.h" // methods for Node all //ME Node::Node( const string &s, Node * p, Node * z) : word( s ), next( p ), prev(z)//constructor { word = s; // init. word data with a copy of s next = p; // next pointer points to p
I have a .cpp file which I have to create a header file for. I started it but I have stuck and it is full of errors.
I have some tasks (see comments in the code):
Task 2: I have to write a template which defines min max operators on vectors, it must be a custom vector template. The main program only demonstrates that it creates a data structure which calls for min max operators.
Task 3: I need a special min max function which watches for any changes and it has to work lineally so it has to step along the elements of the vectors determining the min max values.
