Error: invalid use of 'void' (using vectors) [closed] - c++

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I am trying to create a code using vectors and other c++11 utilities. The above mentioned(on the title) error occurs in my code and despite I looked for a solution to this error on the internet I did not find something that works into my code. I tried to make some type castings but did not work. I present you the contentious part of code below:
#include <iostream>
#include <ctime>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <map>
#include <algorithm>
#include <list>
//#include <Winbase.h>
using namespace std;
// A struct describing a product.
typedef struct Products
{
string category;
string name;
float price;
} Product;
inline void scenario1(int num_cashiers)
{
vector<Product> products; // It is a vector(a pseudo-second dimension) of products which will be used for each customer
vector<vector<Product>> customers; // A vector containing all customers
vector<vector<vector<Product>>> cashiers(num_cashiers); // A vector describing the supermarket cashiers declaring a queue of customers for each cashier
double start = GetTickCount(); // It will be used for counting 10 secs until next update
vector<int> total_products(num_cashiers); // A vector keeping the total number of products of each queue
list<string> categories; // A list containing all the categories of the products
list<float> categories_prices(categories.unique().size()); // A list containing all category prices
//THE ABOVE LINE - THE LAST ONE IN THIS PART OF CODE - IS THE LINE I GET THE ERROR!!!
....
}
What is wrong with the code?
Thank you everyone in advance!

list::unique is a void function, it does not return anything. On that last line, where you call categories.unique().size(), you are calling .size() on a void expression.

Related

Error message when creating a vector of objects [closed]

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for a homework i have to create a vector of objects who have some attributes, included an ip adress, and order the vector according to their IP adress. I'm having some trouble creating the vector, heres the code.
#include <iostream>
#include <fstream>
#include <string>
#include <string>
#include <algorithm>
#include <vector>
#include "data.h"
using namespace std;
void createVect(ifstream inFile) {
string month, day, ip1, ip2, ip3, ip4, temp, ip;
string t1;
int i = 0;
size_t n = 3;
vector<data> vect;
}
but im getting an error when trying to define the vector: "data" is ambiguousC/C++(266).
The code is bigger but this is the only relevent part (I think).
class data{
public:
std::string mes;
int dia;
std::string hora;
int ip;
data();
};
It's a pretty simple class, i just need it to store the data from the file i'm using.

C++ use of undeclared identifier [closed]

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Closed 3 years ago.
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I know there's a lot of different threads with this similar issue but I've gone through a number of them and have fixed any of the possible issues that may be resulting in this error but I keep getting it.
I'm trying to test some of functions in my class file but whenever I try calling them I get that error.
Here's one for example.
main.cpp
#include <iostream>
#include <vector>
#include "Graph.h"
using namespace std;
int main(){
Graph graph;
newState();
return 0;
}
Graph.h (I know I shouldn't be using namespace here but I'm still doing it for now)
#include <stdio.h>
#include <iostream>
#include <vector>
using namespace std;
class Graph{
public:
Graph();
Graph(vector<Edge> const &edges, int N);
void printGraph(Graph const &graph, int N);
// print adjacency list representation of graph
void createTree(GraphNode *root, int state[]);
void newState();
private:
int states = 8;
int initialState[8];
int nextState[8];
};
Graph.cpp
#include "Graph.h"
void Graph::newState(){
srand (time(NULL));
int random = rand() % 4 + 1;
cout << random;
};
I feel like I'm trying to do the bare minimum but it just does not want to work. Can anyone please tell me where I'm going wrong?
newState is not a free-standing function. It is a non-static member function of Graph class. Which means, it must be called on an instance of Graph. What you probably meant to do is:
Graph graph;
graph.newState();

I cannot initiate an integer vector in C++ [closed]

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Closed 5 years ago.
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I have the following code excerpt.
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <fstream>
#include <string>
#include <array>
using namespace std;
int solver(int T)
{
/* read IA */
ifstream inputFile("IA [0;1.3077].txt");
vector<int> ia;
if (inputFile) {
int num;
while ( inputFile >> num) {
ia.push_back(num);
}
}
}
int main (void) {
solver(360);
}
But it gives me this error:
error: implicit instantiation of undefined template
'std::__1::vector<int, std::__1::allocator<int> >'
vector<int> ia;
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iosfwd:200:29: note:
template is declared here
class _LIBCPP_TYPE_VIS_ONLY vector;
The goal is to read a txt file with integers per line without knowing how many lines there are in advance. I'm choosing a vector to hold the data because I don't want to initialize an integer array with a fixed size. Does anybody have any suggestions?
Also, I understand that the variable T is unused - I will use it after the .txt file is loaded.
You need to:
#include <vector>
You must alway include directly all the headers for the types you use.

In c++ if header is included why I got 'does not a name of type' error? [closed]

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Closed 5 years ago.
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I have data.h:
#ifndef DATA_H_INCLUDED
#define DATA_H_INCLUDED
#include <vector>
#include <string>
#include <iostream>
using namespace std;
class student{
public:
string id;
int points [6] = {0,0,0,0,0,0};
};
#endif // DATA_H_INCLUDED
And I have enor.h:
#ifndef ENOR_H_INCLUDED
#define ENOR_H_INCLUDED
#include <fstream>
#include <vector>
#include <string>
#include <iostream>
#include "data.h"
using namespace std;
enum status{norm,abnorm};
class enor{
public:
/*some voids*/
Student Current() const { return elem; }
student elem;
private:
/*some voids*/
};
#endif // ENOR_H_INCLUDED
And I got 'Student' does not a name a type, but why? I tried also if the Student calss is in enor.h, but also this error. how can I resolve this, and why is this?
You have a difference in your case for your student class:
class student - Lower case s
Student Current() const - Upper case S

programme crashes when trying to cout map value [closed]

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Closed 9 years ago.
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I am trying to insert pair values < float,string > into my map class
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <set>
#include <iostream>
#include <map>
using namespace std;
int main()
{
map<float,string> output;
output.insert(pair<float,string> ( 200.5, "foo" ));
output.insert(pair<float,string> ( 100.5, "batr" ));
map<float,string>::iterator mps1;
map<float,string>::iterator mps2;
mps1 = output.begin();
mps2 = output.end();
while (mps1 != mps2)
{
cout<<mps2->first
<<" "
<<mps2->second; //crashes here
mps1++;
}
system("PAUSE");
}
Using the debugger , it crashes when it does to the following line
<<mps2->second;
Can someone explain to me , thanks
You're supposed to access mps1, not mps2.
mps1 is the iterator you're incrementing for use; mps2 is the "end iterator" which you must not dereference.
It's a pretty basic typo / logic error.