CODEWITHSUNDEEP
c++vectoriteratordoublecout
user4706893
user4706893

Reputation:

C++ conversion from int to non-scalar type in a simple vector program

I just want you to tell you that I am writing this post after reading many postings regarding the error I've been getting : " conversion from ‘int’ to non-scalar type." But for my own program, I don't get to apply any of the answers out there to fix it. I hope any of you can give me a comment/opinion/suggestion or concern on the following specific code. 

    vector<double>::iterator a = *max_element(vector1.begin(), vector1.end());
    vector<double>::iterator b  = *min_element(vector1.begin(), vector1.end());
    vector<double>::iterator c  = *(nth_element(vector1.begin(), vector1.begin() + vector1.siz

And one last quick question: Isn't the following way correct to print out the value of variable a, b, c respectively? My compiler is saying that there is no match for ‘operator<<’ in ‘std::cout << a....'. I would appreciate your feedback on this too.

cout << a << b << c << endl;

Thank you so much! I will keep watching on this until getting your reply.

The following is my code for your consideration

 #include <iostream>
 #include <fstream>
 #include <algorithm>
 #include <vector>

 using namespace std;

int main(){

ifstream ifs("foo.txt");


//initiailize a vector of integers:
vector<int> vector1;

double d;
while(ifs >> d)
{
    vector1.push_back(d);
}

int allnumb = vector1.size();

for(int i = 0; i < allnumb; i++){

    vector<double>::iterator a = *max_element(vector1.begin(), vector1.end());
    vector<double>::iterator b  = *min_element(vector1.begin(), vector1.end());
    vector<double>::iterator c  = *(nth_element(vector1.begin(), vector1.begin() + vector1.size()/2, vector1.end()));
    cout << a << b << c << endl;

    }

   return 0;
 }

Upvotes: 0

Views: 6415

Answers (3)

Shivam
Shivam

Reputation: 1

It looks like there are some issues in your code. The iterators a, b, and c should be used to access values, not printed directly. Additionally, the loop structure is causing the same values to be printed in each iteration. Here is the corrected code:

#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

int main() {
    ifstream ifs("foo.txt");

    // initialize a vector of doubles:
    vector<double> vector1;

    double d;
    while (ifs >> d) {
        vector1.push_back(d);
    }

    int allnumb = vector1.size();

    // Check if the vector is not empty
    if (!vector1.empty()) {
        vector<double>::iterator a = max_element(vector1.begin(), 
vector1.end());
        vector<double>::iterator b = min_element(vector1.begin(), 
vector1.end());
        nth_element(vector1.begin(), vector1.begin() + vector1.size() / 2, 
vector1.end());
        vector<double>::iterator c = vector1.begin() + vector1.size() / 2;

        cout << "Max Element: " << *a << endl;
        cout << "Min Element: " << *b << endl;
        cout << "Median Element: " << *c << endl;
    } else {
        cout << "Vector is empty." << endl;
    }

    return 0;
}

This code reads values from "foo.txt" into a vector, then it finds the max, min, and median elements using the max element, min element, and nth element functions, respectively. The corrected code now properly prints the values of the max, min, and median elements.

Upvotes: -2

Max Fomichev
Max Fomichev

Reputation: 244

There are some errors in your code. 1. std::vector<int> is declared, but std::vector<double>::iterator is used. What is correct type - int or double? 2. max_element() and min_element() return std::vector<Type>::iterator and your are trying to derefference iterator on the right side and assign its value to iterator variable type on the left side. Use int a = *max_element(vector1.begin(), vector1.end()); 3. nth_element() does not return anything. Use nth_element(vector1.begin(), vector1.begin() + vector1.size()/2, vector1.end());

Upvotes: 0

Mike Seymour
Mike Seymour

Reputation: 254651

max_element and the other functions return iterators. You then use * to dereference those to get the int values they refer to, and finally try to use those int values to initialise a different iterator type. That makes no sense, hence the first error.

Then you try to print the iterators, which aren't printable, hence the second error.

Perhaps you want the values:

int a = *max_element(...);
int b = *min_element(...);
int c = *nth_element(...);
cout << a << ' ' << b << ' ' << c << endl; // add spaces for readability

or perhaps you want correctly-typed iterators:

vector<int>::iterator a = max_element(...);
auto b = min_element(...);  // a more convenient alternative, since C++11
auto c = nth_element(...);
cout << *a << ' ' << *b << ' ' << *c << endl; // dereference to print the values

Upvotes: 2

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