I am trying to create an array of objects. I have to be abstract unfortunately (can't show you all my code), but this is the general gist of what I'm doing. Let's say these objects will be Widgets.
I would assume a vector of widgets would be better than an array due to it's flexibility. So if I use an array, let's say that my widjet is called MY_WIDGET and MY_WIDGET has a constructor of MY_WIDGET(int x, int y);
I have tried using an array to hold several widgets like this.
int i = 10; // obviously this number will be decided dynamically.
int x = 10;
int y = 10;
MY_WIDGET *array[i];
for(int x = 0; x < i; x++)
{
arr[x] = new MY_WIDGET(x,y);
y +=30; // moves the next widget down so they don't cover each other.
}
So now I have an array of objects or Widgets in this case. I'm only using widgets for this example because I want to display the use of a constructor.
So, while my compiler (MinGW) will let me do this, I still get an error at runtime because of the way I have dynamically sized my array 'arr[i]'.
The usual way of doing this, let's say for an int (see below), I can't apply for an object with a constructor requiring multiple parameters to construct it. Maybe I can't, I'm not sure.
int *x = 0;
x = new int[10];
This begs the question, should I be using a vector and if so, how do I dynamically push_back constructed objects into a vector without running into the same problem above. I have tried the below and get problems at compile time telling me that 'the base class is private within this context'. Not sure how to go about this but if I can understand how to dynamically create objects with constructors and add them to a vector or array I should be able to do this.
I create new dialog window. I add container Fixes and change Fixed properties : - AutoSize, +Expand, +Fill to enable other widgets. I add Text View, Textview is inside GtkScrolledWindow which has property X and Y but not Height and Width. If GtkScrolledWindow has scrollbars, its size is fixed, if not - size depends on the content Textview and grows when I type text. I want not to grow control if I type Text but want my own size. It is possible?
How to output vector contents using the push_back function. My program reads in values just fine, but it does not output anything and I've been stuck on why.
here is my code:
#include <iostream> #include <array> #include <vector> using namespace std; int duplicate( vector < int > &vector1, const int value, const int counter)
I am programming about some numerical problems. I know that vector supplies vector operations. But vector always allocate more memory (used when the size changes). My matrix or array never change size, and the vector operation is just +,-,dot,cross,distance
My question is that should I use vector, or simple double array with new & delete is enough for me?
How to load .wav files. Say there are several .wav files in a folder called "sounds" in "My Documents", what would be the steps on loading them in a vector or array. I'm thinking I should use a vector type of array to not worry for a fixed size.
For a rather complex and strange reason that I won't explain right now, I need to have this going on in my program.
class FVF{ private: vector<vector<float>> data; //Contains fvf data for Direct3D stuff public:
[Code].....
The FVF allows this Model3D class to also be compatible with file handling methods I've got, but here's the problem. D3D buffers require an array to feed them the information, and I know that for a single dimension of vector I can use vec.data(), how to do this for multiple dimensions.
I think the best Idea I've got so far is to set the vector within the Model3D class as a pointer, then I can union it with a float pointer... Once I can guarantee the information is correct and complete, manually transfer the contents of the vectors into the float pointer.. (The union is to reduce memory needed instead of having the data repeated in vectors and arrays)
This can be done very easy, but I assume there is a better way to do it.
assume that I have a vector or a signal like
x=[1 1 1 1 1]
want to shift it by one unit to the right I have
x[n+1] gives
xn=[0 1 1 1 1 1]
and x[n-1] vies
xn=[1 1 1 1 0]
as you can see the length of the original vector or array does not change.
How can I solve this problem without specify the length of the output vector. The size of the output array should be the same as the input array, but I couldn't find a way to do it without adjusting the size.
I am trying to pass a 2D array called f (coming from a text file with 9 columns of numbers and 297,680 rows) that was created using the vector container in my main() to the function myfunc. I'm just trying to figure out how to pass the address of f in main() to myfunc(), so that myfunc() has arguments consisting of a pointer g (that accepts the address of f as an input) and an int.
This is the error from the compiler: test_2d.cc: In function ‘int main()’: test_2d.cc:47:25: error: cannot convert ‘std::vector<std::vector<double> >*’ to ‘double (*)[297680][9]’ for argument ‘1’ to ‘int myfunc(double (*)[297680][9], int)’ return myfunc(&f,count); ^ Here is my code:
#include <iostream> #include <fstream> #include <iomanip> //allow setprecision to get all the decimal points #include <vector> #include <string>
In a numerically intensive code, I have a Cartesian vector class Vector3d which has the normal operator overloading and basic functions such as dot product, magnitude, etc. For simplicity, assume that it is not a templated class and its components are of type double.
I frequently need large 1-d arrays (e.g. stl vectors) of Vector3d. Two use-cases must be satisfied:
1) The trivial case in which the data are stored as stl vectors of Vector3d;
2) The more difficult case where the individual components are stored as stl vectors of double, and are not guaranteed to be contiguous in memory (so one cannot rely on "stride").
Assuming the array lengths are all identical, I'd like to be able to access both types in a single loop. The straightforward way for case 2) is to construct a temporary Vector3d from the three components (indexed with the loop index). However, I would prefer not to incur the overhead of the constructor.
Is it possible using template metaprogramming. Ideally I'd like a CompositeVector3d that inherits from Vector3d and is constructed with the component vectors, but can be dereferenced using the loop index in the same way as one would do with case 1.
I am not looking for the typical template metaprogramming utility of being able to operate on the entire array without explicit loops. I just want the syntactic "sugar" whereby CompositeVector3d and Vector3d act the same, plus the avoidance of the cost of the constructor. I am not averse to using an additional templated class (perhaps a Field or a View class) to access the basic storage in both case.
Is it possible to do this without using a full template metaprogramming utility?
How to pass my array to the function and return it as a sorted vector. I'm kind of lost with the functions part.
Problem: Write a program that performs a sorting routine as discussed in class. Create an array of 10 integers (e.g., 63, 42, 27, 111, 55, 14, 66, 9, 75, 87). Pass this array to a separate function that sorts the integers and returns a vector containing the sorted integers. Use either the SELECTIONSORT algorithm or the INSERTIONSORT.
I'm trying to use a priority queue sorting in reverse order to take a vector or 2d array. The problem is that I want to sort by the vector/array cell value but keep the reference to the vector/array index of the value. I don't know quite howto keep them both related so when I pop. I can find the corresponding cell.
I have a cpp app that reads in a number of files and writes revised output. The app doesn't seem to be able to open a file with a ' in the file name, such as,
N,N'-dimethylethylenediamine.mol
This is the function that opens the file :
Code: // opens mol file, reads in rows to string vector and returns vector vector<string> get_mol_file(string& filePath) { vector<string> mol_file; string new_mol_line; // create an input stream and open the mol file ifstream read_mol_input; read_mol_input.open( filePath.c_str() );
[Code] ....
The path to the file is passed as a cpp string and the c version is used to open the file. Do I need to handle this as a special case? It is possible that there could be " as well, parenthesis, etc.
I have asked a related question before, and it was resolved successfully. In the past, when I wanted to use std::max_element in order to find the maximum element (or even sort by using std::sort) of a vector of structures according to one of the members of the structure, all I had to do was to insert a specially designed comparison function as the third argument of the function std::max::element. But the latter comparison function naturally accepts two arguments internally.
For instance, here is a test program that successfully finds the maximum according to just one member of the structure:
And the output was this, as expected: Maximum element S.a of vector<S> vec is at: 9 [I]max element of vec.a between slot 3 and slot 6 is: 6, and its index is: 6 vec[6].a = 6 [I]max element of vec.a between slot 4 and slot 7 is: 7, and its index is: 7 vec[7].a = 7 [I]max element of vec.a between slot 5 and slot 8 is: 8, and its index is: 8 vec[8].a = 8 [I]max element of vec.a between slot 6 and slot 9 is: 9, and its index is: 9 vec[9].a = 9
However, I now need to search and find an element of vector<myStruct> according to just one member of myStruct, instead of finding the maximum or sorting as before. This presents a problem because the function std::find does not accept such a comparison function as its third argument.
This was the description of the std::find function that I found: find - C++ Reference
Code: template <class InputIterator, class T> InputIterator find (InputIterator first, InputIterator last, const T& val);
I could also find another function called std::find_if, but this only accepts a unary predicate like this: find_if - C++ Reference
Code: template <class InputIterator, class UnaryPredicate> InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);
And once again this is either inadequate of I don't see how to use it directly, because for the third argument I would like to insert a function that takes two arguments with a syntax like this:
Code: int x=7; std::vector<S>::iterator result; result = std::find(vec.begin(), vec.end(), []( const (int x, const S & S_1) { return ( x == S_1.a ) ; } ) ;
Is there another std function that I can use to make search and find an element according to just one member of myStruct?
Or perhaps there is a clever way to pass two arguments to the unary predicate.
I am trying to print a matrix solution that I've stored in a vector of doubles. The original matrix was stored in a vector of vector of doubles. I want to print to the screen and an output file. Right now it just prints to screen column-style and the output file is horizontal-style. I tried to change the solution from vector of doubles to a vector of vector of doubles like the original matrix but when I run my code it crashes. Here is what I am referring to:
void readMatrix(vector<vector<double>> &matrix, vector<double> &b, int &N, string input) { ifstream in(input); in >> N; matrix.resize(N); b.resize(N);
[Code] ....
However when I change my printResult function to this (I removed the string argument because I just want to get it working to the screen first):
void printResult(vector<vector<double>> &sol, const int N) { //ofstream out(output); //int j; for (int i = 0; i < N; i++) { for (int j = 0; j < N; j++){
[Code] ....
The program crashes. Am I even printing the matrix correctly?
I want to have it so that when i ask for the person witch item they want to drop on the ground it goes into another vector that i can pick back up the item if they want it back and erase when they walk away.
Why is it reading in nothing for the arrays, and also making the size of the total thing the total number of numbers? It should have a size of 2, not 5.
std::vector<unsigned char> vec1; //insert some values into vec1 std::vector<unsigned char> vec2;
Now I want to to copy 2 bytes from vec1 starting at index 5., why do i need to know how many bytes from the end of vec1?? can't i just specify how many bytes i want to copy from starting index?
