Expected Primary-Expression before ']' token? - c++

Question

I'm trying to be able to call a function with the vector and for some reason it's saying "expected primary expression before ']'. The vector could hold any number of files, depending on the amount of numbers in myfile, so I'm not sure what I should put there.
#include <fstream>
#include <string>
#include <vector>
#include <iostream>
using namespace std; // not recommended
double averageCalc(string[],int);
int main () {
double average;
string line;
ifstream myfile ("array_pgmdata.txt");
//int index = 0; // not needed
//string myArray[index]; // UB - if it even compiles, it's a VLA of size 0.
std::vector<std::string> myArray; // use this instead to be able to grow it
// dynamically
if (myfile) // open and in a good state
{
// while (! myfile.eof() ) // It'll not be eof when you've read the last line
// only when you try to read beynd the last line,
// so you'll add "line" one extra time at the end
// if you use that. Use this instead:
while(getline(myfile, line))
{
// myArray[index++] << line; // you have 0 elements in the array and
// can't add to it in any way
myArray.push_back(line);
}
}
else cout << "Unable to open file";
for(size_t idx=0; idx < myArray.size(); ++idx) {
std::cout << myArray[idx] << "\n";
}
average = averageCalc(myArray[], line); // error here
return 0;
}
double averageCalc(string nums[], int count)
{
int a, total, elements, averaged1, averaged2;
// string averaged2;
for(a = 0; a < count; a++)
{
total+=a;
elements++;
}
averaged1 = total / elements;
return averaged2;
}

Answer 1

There's a few problems here. Firstly, your function averageCalc expects a parameter of type string[] which is an array of strings. When you call the function, you are trying to pass it a std::vector<string>, which is not an array of strings, it is a class. Presumably, you would want to change your function to take in a vector, like so:
double averageCalc( const std::vector<string> & nums ); // no need for size now
The other issue you have is in calling your function. When you call it, you pass myArray[] as a parameter, which is the error you compiler is giving you. This is not valid syntax, you simply want to pass in myArray.

Answer 2

I think that the error occurs becase firstly you create the array with std::vector<std::string> myArray; so the data is string type but when you want to calculate the average value the function expects a value int, double etc. in order to perform math. Either change the string to int or use a function to convert it:
int main()
{
string s = "12345";
// object from the class stringstream
stringstream geek(s);
// The object has the value 12345 and stream
// it to the integer x
int x = 0;
geek >> x;
// Now the variable x holds the value 12345
cout << "Value of x : " << x;
return 0;
}