C++ :: Vector Whose Elements Have Function Pointer Type
Mar 30, 2013"Write a declaration for a function that takes two int parameters and returns an int, and declare a vector whose elements have this function pointer type."
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C++ :: How To Print Out Elements Of Vector Of Type Pair
Oct 7, 2014here is a piece of my code:
while(T--)
{
std::vector<std::pair<int, int> > *dragon;
std::vector<std::pair<int, int> > *villager;
[Code]....
I now wish to print the elements of the vector. How do I do it?
C++ :: Function Pointer Typedef With Same Type Arguments
Mar 6, 2015I need to create the following brain damaging abomination:
I need a function pointer type to a function that has an argument of the same function pointer type and returns the same function pointer type.
The purpose is to enable a type of subroutine threading scheme for a small application specific scripting language. The question could just as well have been posted to the C forum.
This syntax works, but Payload is a generic type which I can coerce into the right pointer type via a cast. This is ugly IMHO. I could also hide it as a pointer in the FlipState class since I've forward declared this.
But this is an extra indirection in a performance critical part of the code, and also ugly.
Code:
class FlipState ;
typedef PayLoad (*FuncPtr) (FlipState *fs, PayLoad P) ; This syntax blows chunks using gcc on the other hand. Code: class FlipState ;
typedef FuncPtr (*FuncPtr) (FlipState *fs, FuncPtr P) ;
[Code] .....
This is hardly surprising. The compiler could not possibly understand what I was defining in the typedef. I think what I need is some kind of way to forward declare a function pointer type and then redefine it properly.
Is such a think even possible or am I just SOL? This one is mind boggling. We know how to do this with classes or other complex data types, but the syntax eludes me for both C++ and C.
Visual C++ :: Pointer To Function Type - Calculating New Variable?
Nov 22, 2012I'm fairly new to C++ and have begun working with pointers. I wish to create am array called sigmaf_point that reads data from a text file. I have managed to get that working, but when it comes to using this pointer I come across some problems. The array is created as such:
Code:
double sigma [5];
double *sigmaf_point = sigma;
void read(double *&sigmaf_point)
string s;
ifstream Dfile;
std::stringstream out;
[Code] .....
I then create a coordinate system inside the main file, as the program I am writing is about modelling the movement of atoms, which requires you to know the coordinates:
Code:
int main();
double **coords_fluid = new double*[5000];
for (int i = 0; i < n_atoms_methane; i++) {
coords_fluid[i] = new double[4];
}
Now, the problem arises when I want to calculate a new variable as so:
Code:
for (int i = 0; i <= n_atoms-1; i++) {
sf1=sigmaf_point(coords_fluid[i][3]);
}
I get the error C2064: term does not evaluate to a function taking 1 arguments, and a red line under sigmaf_point that says it must be pointer to function type. I am a bit confused about this.
C :: Function To Read A Text File - Incompatible Pointer Type
Nov 3, 2014So for a project, my professor sent out two pages of code containing functions to read a text file (since we do not know how to write this on our own yet). I've got the code working on Orwell IDE and it gives me 2 warnings saying
"Passing argument 1 of 'readFromFile' from incompatible pointer type"
"Passing argument 2 of 'option2Print' makes integer from pointer without a cast"
The Orwell IDE seems to just bypass these warnings and compiles the code correctly. However, when I transferred my files over to my desktop using BloodShed (what the professor uses), instead of getting a warning I get an error and the code won't compile.
I assume it will not compile on his computer either since he uses the BloodShed IDE.
I don't know how to put the code directly into the text neatly, so a attached a .zip file with my code. The "storms.txt" file is also included. (the file that will be read).
C :: Passing Argument Of Incompatible Pointer Type - Warning In Function Call In Main
Jun 4, 2013Code:
#include <stdio.h>
#include <stdlib.h>
int size_b_row1;
int size_b_col1;
[Code].....
C++ :: Pointer Usage To Base Class Object In Vector Int Main Function
Aug 12, 2013I know what are pointer's and how to use them but there is one point i am not able to understand. Below is the example code
I understand everything in the below code except 1 thing why i am using pointer to base class object in vector int the main() Function?
Code:
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
// base class
[Code] ...
Here is the lines of code i want to understand.
Code:
vector<Employee*> employees;
employees.push_back(&emp1);
employees.push_back(&mgr1);
I know if i will not use the pointer base class function "virtual double grossPay" will be called for both base class object and derived class object and when i will use pointer with reference to the object because base class function is virtual it will look for same function in derived class and if available it will execute it.
C++ :: Passing Arguments From Incompatible Pointer Type - Warning In Function Call Transpose In Main Routine
Jun 4, 2013#include <stdio.h>
#include <stdlib.h>
int size_b_row1;
int size_b_col1;
int main(void) {
double C[4][4] = {{1,3,5,2},{7,6,2,2},{1,2,7,3},{2,3,5,3}};
double TC[4][4];
transpose(C, TC);
[Code] ......
C++ :: Write Swap Function To Swap 2 Elements In Vector?
Nov 15, 2013write a swap function to swap 2 elements in the vector?
View 3 Replies View RelatedC :: Define Array Type With 4 Elements?
Jan 18, 2015How can I define type MARKS which will be able to hold 4 elements just like array? I want to access it just like normal array elements using brackets []. In the following struct I want to use such type.
Code:
typedef struct {
MARKS ** pointers;
} ARGUMENTS
void main(){
ARGUMENTS arguments;
[Code] ......
Purpose of the struct ARGUMENTS is to hold 4 pointers to string. I want to mark few positions in string so I can simple access them. E.g. name=John
Code:
arguments[0][0]=0; // begin of the param name
arguments[0][1]=3; // end of the param name
arguments[0][2]=5; // begin of the value
arguments[0][3]=8; // end of the value I mean not to save int but the pointer to the corresponding position.
C++ :: Inserting Elements In A Set With Type Pair
Jan 8, 2013I want to use a dataset of type set which will have the type pair<char,string> or pair<string,string>. How can i insert values into the set, because i have to initialize the set and will not change the set during the program.
View 3 Replies View RelatedC++ :: Filling A Vector With Elements?
Mar 21, 2013I'm writing a program with a class containing a private std::vector<bool>. I chose bool because the vector represents a 2D array (think grid) and I only need 2 states per cell. I kept it one-dimensional as this hardly complicates things.
My problem is that I don't know how to initialize the vector, i.e. fill it with 0's.
The grid's resolution is not known at compile time, so I imagine I have to set the size (and content) of the vector in the class constructor.
Here's what I have tried among several things:
Code: World::World(const u_short worldsize)
{
grid.reserve(worldsize * worldsize); // grid is the private vector; square dimensions.
std::fill(grid.begin(), grid.end(), 0);
std::cout << grid.size();
} The output is 0. Only std::vector::push_back seems to have an effect on size(), but judging by its description, it doesn't look like the right candidate to populate a vector with zeros. Correct me if I'm wrong.
Frankly I expected line 3 to set the vector's size.
C++ :: Swap Elements Of Vector
Apr 21, 2014how to swap the first and 'mid' elements of a vector?
View 2 Replies View RelatedC++ :: Generating All Possible Combinations Of Vector Elements
Feb 14, 2013I have an integer vector of size "n".
e.g.
std::vector<int> vec;
vec.pushback(0);
vec.pushback(1);
vec.pushback(2);
vec.pushback(3);
Now I want to generate all possible combinations of size = {0, 1, 2, ... , n}.
{0, 1, 3} is not equal to {3, 1, 0} or {1, 0, 3} or {3, 0, 1}
C++ :: Memory Size Of Vector Elements
Apr 9, 2014I had a question about memory allocation/how iterators work for a std::vector<foo> of a user defined class 'foo'. Say foo contains variables of variable size, so that each member of the std::vector<foo> does not require the same amount of memory space.
Does c++ allocate the same amount of memory for each element, equal to the amount of memory required for the largest element? Or does it use some sort of array of pointers pointing to the location of each element in the vector to make the iterator work? Or does it use some other method? I am wondering because I wrote a code which reads data from a binary files and stores most of it in std::vectors.
The code seems to be using significantly more memory than the sum of the size of all the binary files, and I am using vectors made up of the datatype within the binary files (float). So I was wondering if internally the code was allocating space for each vector element which is the size of the largest element as a way to handle indexing/iterators. I ran my code through a memory leak checker and it found no errors.
C++ :: How To Store Elements In 2D Vector And Call Them Out
May 5, 2013I am currently trying to implement a 2d vector to store x and y of type int.
I have successfully passed it to the function, however i am unable to store the values in it. It always returns with a segmentation fault and my program terminates from there. May i know how do i store them properly and call them out?
Below is my code snippet
int reconstructSecret(int x, int y, vector< vector<int> > &inVec ,int constructSecret) {
int getX,getY,formula,accum,count,getSecret,startPosition,nextPosition,numerator,denominator;
getX=x;
getY=y;
int result;
[Code] .....
The main method
vector< vector<int> > inVec;
for(int i=0;i<constructSecret;i++) {
cout<<"please key in the "<<i<< "share of x value:";
cin>>x;
[Code] ...
C/C++ :: Erasing / Removing Elements From A Vector?
Mar 23, 2015I am working on a project for class where I use a parent Shape class with circle, rectangle, ect. Classes inheriting from that. Along side these I use a class called Scene. In main I need to create a scene and add some shapes to a vector in scene.
vector<Shape*> shapes
I need to use functions addShape(Shape* shape) and a delete shape method. I have the addShape finished. The problem I am having is with the delete method. Is there a way that I can use something like deleteShape(Shape* shape)? Is it possible for me to delete a specific shape from the vector by passing in that shape, or can it only be done using index? I have looked at the documentation for std::vector as well as std::vector::erase. I am wondering this because if I use index values and do something like
void Scene::deleteShape(unsigned int x) { shapes.erase(shapes.begin() + x ); }
It will lead to some errors later on due the the changing size and indexes of the vector and elements.
C++ :: Accessing Nested Elements Of Vector
May 1, 2015so lets assume i have a nested vector in a set or vice versa o in a more general form a container in a container example...
Code:
std::set<vector<int> > my_tuple;
How do i access individual elements of lets say the first vector in the set! Or the last element in the 3rd vector?
C++ :: Pointer To Array - Accessing Elements?
Mar 31, 2013Code:
int arr[10];
int* p = arr;
int (*p2)[10] = &arr;
So, pointer p is a pointer to an array, I can use it to access elements of arr as in *(p+5).
Pointer p2 is a pointer to an array of ten integers. What is it for, how can I use it to access elements of arr?
C/C++ :: Insert Number Of Elements From One Into Another Vector Without Resizing
Dec 28, 2012I think std::copy appears to do what I'm looking for.
I'm in need of a vector member function that would allow me to "insert" a number of elements from one vector into another vector without resizing or destroying either.
An example of what I'm wanting to do is assign the contents of two[3-5][50-54] to one[7-9][2-6]. Other than looping through both vectors using .at(), is there a way to copy this?
This would be continuous within a user controlled loop with differing elements being exchanged.
typedef vector<vector<unsigned char> > vec;
vec one(10, vector<unsigned char>(10, '1')),
two(90, vector<unsigned char>(90, '2'));
C++ :: Acyclic Visitor Pattern - Count Number Of Elements Of Certain Type In Container
Jun 29, 2014Acyclic visitor pattern used here to count the number of elements of a certain type in a container.
struct A {
struct Visitor {
virtual ~Visitor() = default;
};
virtual void accept (A::Visitor&) = 0;
[Code] ....
Give the correct:
count = 3
But it is scrappy. The visitor classes had to be placed outside the classes they belonged to, and CountB lost its template because of that. Also, it is very awkward that I have to construct a "reverse hierarchy" for the Visitor classes (which means that this has to bechanged if I ever change the hierarchy for A, B, C, ...). How to improve my solution (using acyclic visitor pattern)? Forward declaring nested classes is not possible in c++.
C++ :: Searching STD Vector Of Strings - Counting Matching Elements And Erasing Them
Jul 19, 2013I have read that the Erase-remove idiom is the way to go. I have a rough understanding of how this works but am unsure whether I can implement a match-counter along with it.
For counting alone, I would use something like this:
Code:
std::vector<std::string> v; // contains duplicate strings in different elements
std::string term = "foo"; // search term, changing at runtime as well
unsigned int matches = 0;
for( auto e : v ) {
if( e == term ) {
[Code] .....
I'm not sure how (or if) I can combine the two things. That is, I don't know how to integrate a function comparing two (changing) strings into the remove_if() method. Nor do I know how to increment a counter during iteration.
The vector is extremely large, so speed is paramount. I think there are many other avenues for optimization, but decreasing the vector's size for each consecutive search could deliver a big speed boost for subsequent searches I imagine, as traversing it holds the biggest cost.
C :: Calling Function Via Function Pointer Inside Structure Pointer
Mar 14, 2013I'm trying to call a function via a function pointer, and this function pointer is inside a structure. The structure is being referenced via a structure pointer.
Code:
position = hash->(*funcHash)(idNmbr);
The function will return an int, which is what position is a type of. When I compile this code,
I get the error: error: expected identifier before ( token.
Is my syntax wrong? I'm not sure what would be throwing this error.
C++ :: Iterator To A Vector Of Struct Type?
Nov 18, 2013I'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.
void foo::insert(const myClassType& en) {
vector<myClassType>::iterator it;
vector<myClassType>::iterator it1;
it = find(Table.begin(), Table.end(), en.memberOne);
[Code] .....
C++ :: Using Vector Push Back Function To Output Contents Of Vector (similar To Array)
Feb 9, 2015How 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)
[Code].....
C/C++ :: Error - Cannot Convert To A Pointer Type
Apr 3, 2015I have attached the source code I am writing. I have been getting the two following errors. I know it's something to do with the pointer casting.
udp-server.c:174:3: error: subscripted value is neither array nor pointer nor vector
udp-server.c:165:3: error: cannot convert to a pointer type
The file is attached here.
udp-server-edit.txt (7.64K)
Number of downloads: 19