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expected primary-expression before ‘]’ token myArray <int> obj(arg1[], size); Confused as to why this is happening

patrickistryingtocode (5)
The code is supposed to print out the highest value in an array

The error is also occurring in my constructor for list[] = arg[]



#include <iostream>
using namespace std;

template <class T>
class myArray{
T list[];
T size;
public:
myArray(T arg[], T x){list[] = arg[], size = x;}
T array_max();
};

template <class T>
T myArray<T>::array_max(){
T index = 0;
for(int i = 0; i < size; i++){
if(list[i] > list[i+1]){
list[i+1] = list[i];
index = i;
}
}
return list[index];
}

int main(){
int temp = 0;
int size = 5;
int arg1[size] = {4, 5, 10, 12, 9};
myArray <int> obj(arg1[], size);
temp = obj.array_max();

cout << temp;

}
Last edited on
Ganado (6810)
You just pass arg1, not arg1[]

And "list[] = arg[]" doesn't make sense. You can't assign arrays like this.

Okay let's back up. If you're trying to put an array inside something else, like a class, there are more restrictions on what you can do. Because an array needs to have a size. It can't dynamically be assigned a new one. If you need to do that, use vector.

Instead of passing the size as a parameter, since you're using template, perhaps you should have size as a template parameter.
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#include <iostream>
using namespace std;

template <class T, int Size>
class myArray{
    T list[Size];
    
public:
    myArray(T arg[], T size){
        for (int i = 0; i < size; i++)
        {
            list[i] = arg[i];   
        }
    }
};

int main(){
    int temp = 0;
    
    const int Size = 5;
    int arr[Size] = {4, 5, 10, 12, 9};
    
    myArray<int, Size> obj(arr, Size);
}
Last edited on
patrickistryingtocode (5)
Thank you for your help. I figured my initialization of the list was wrong.
seeplus (6591)
Please use code tags when posting code so that the code is readable.


[code]
   code goes here
[/code]



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#include <iostream>
using namespace std;

template <class T>
class myArray {
	T list[];
	T size;
public:
	myArray(T arg[], T x) { list[] = arg[], size = x; }
	T array_max();
};

template <class T>
T myArray<T>::array_max() {
	T index = 0;
	for (int i = 0; i < size; i++) {
		if (list[i] > list[i + 1]) {
			list[i + 1] = list[i];
			index = i;
		}
	}
	return list[index];
}

int main() {
	int temp = 0;
	int size = 5;
	int arg1[size] = {4, 5, 10, 12, 9};
	myArray <int> obj(arg1[], size);
	temp = obj.array_max();

	cout << temp;

}

seeplus (6591)
Maybe something like:

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#include <iostream>
#include <algorithm>

template <class T, size_t SIZE>
class myArray {
	T list[SIZE] {};

public:
	myArray(const T arg[SIZE]) { std::copy(arg, arg + SIZE, list); }

	T array_max() const;
};

template <class T, size_t SIZE>
T myArray<T, SIZE>::array_max() const {
	T maxVal {list[0]};

	for (size_t i {1}; i < SIZE; ++i)
		if (list[i] > maxVal)
			maxVal = list[i];

	return maxVal;
}

int main() {
	constexpr size_t size {5};
	constexpr int arg1[size] {4, 5, 10, 12, 9};

	const myArray <int, size> obj(arg1);

	std::cout << "Max value is " << obj.array_max() << '\n';
}

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