CODEWITHSUNDEEP
c++
Undermine2k
Undermine2k

Reputation: 1491

how can I pass an array pointer to a function

#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>


using namespace std;

typedef vector <double> record_t;
typedef vector <record_t> data_t;


int sorted(int *data,int max_record_size)
{


}




int main()
{
    // Here is the data we want.
    data_t data;

    // Here is the file containing the data. Read it into data.
    ifstream infile( "sort.txt" );
    infile >> data;

    // Complain if something went wrong.
    if (!infile.eof())
    {
        cout << "Fooey!\n";
        return 1;
    }

    infile.close();

    // Otherwise, list some basic information about the file.
    cout << "Your CSV file contains " << data.size() << " records.\n";



    unsigned max_record_size = 0;
    for (unsigned n = 0; n < data.size(); n++)
        if (max_record_size < data[ n ].size())
            max_record_size = data[ n ].size();
    cout << "The largest record has " << max_record_size << " fields.\n";
    int i;
    for (i=0; i <= max_record_size; i++)
    {

        cout << "your data contains " << data[ 0 ][ i ] << ".\n";
        int temp[max_record_size];

        sorted(&data,max_record_size);

        //cout << "Your sorted data contains" << sorted [0] [i] << ".\n";
    }


    cout << "Good bye!\n";
    system("PAUSE");

    return 0;
}

cannot convert data_t*' toint*' for argument 1' toint sorted(int*, int)'

Im trying to pass the pointer of my data which should be an array containing my list of numbers to my sort function what exactly am I doing wrong and can you please explain in detail so I can understand it, thanks!

Upvotes: 0

Views: 157

Answers (3)

Aesthete
Aesthete

Reputation: 18850

Try passing a reference to the original vector. Why?

  • You still want to work with the original vector without making a copy
  • You can't pass a null reference, so the argument is always valid

  • You're not doing any pointer arithmetic, so be safe and use a reference

    int sorted(data_t& data, int max_record_size)
{             
}

Pass your data_t structure like this:

sorted(data, max_record_size);

Now you have access to the data_t structure inside your sorted function.

Also

You know that your code is not going to compile?

  • unsigned max_record_size and int temp[max_record_size] are invalid. If you're going to allocate an array on the stack, you need to use a constant size.
  • There is no overload on the >> operator in the istream class that handles vector<vector<double>>, so this statement is broken as well: infile >> data;

Upvotes: 0

bames53
bames53

Reputation: 88155

data_t is a vector<vector<double>>. This is not even close to an array of ints. You just need to write a function that handles data_t and not ints.

If the function is supposed to sort data then you should use std::sort, and to do that you'll need to write a comparison function that can compare two elements of data in order to see which one should come before the other in the sorted result.

Here's an example of providing such a comparison function using a lambda with lexicographical_compare.

sort(begin(data),end(data), [](record_t const &lhs,record_t const &rhs) {
    return lexicographical_compare(begin(lhs),end(lhs),begin(rhs),end(rhs));]
});

Upvotes: 0

Christian Stieber
Christian Stieber

Reputation: 12496

You don't have an array. An array in C (or C++) would be just a list of integers, and you could pass it like you did.

However, you have a vector (and I'm guessing record_t ends up being an int). vector<>s behave a lot like arrays, but they are not, they are actual objects.

What you probably want to do is write your function as

int sorted(data_t& data, int max_record_size)

and your call simply as

sorted(data,max_record_size);

Upvotes: 1

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