C++ function for average not working

[doforumda]

hi

i am trying to make a function to display an average of an array. I am using Microsoft Visual C++ Express 2010.

here is my code

#include <iostream>
using namespace std;

float avg(int[], int);

int main()
{
	int a[] = {2,4,3,6};
	int size = sizeof(a) / sizeof(int);

	//cout << size << endl << endl;
	cout << "avg(a,s) = " << avg(a,size) << endl;

	system("pause");
	return 0;
}

float sum(int a[], int s)
{
	float sum = 0;
	float avg = 0;
	for (int i = 0; i < s; i++) {
		sum = float(sum + a[i]);
	}
	avg = (sum / s);
	return avg;
}

it displays this error

1>main.obj : error LNK2019: unresolved external symbol "float __cdecl avg(int * const,int)" (?avg@@YAMQAHH@Z) referenced in function _main
1>D:\C++ ... \Debug\exercise 6.3.exe : fatal error LNK1120: 1 unresolved externals

[doforumda]

i got it :)

[lionishy]

doforumda>int size = sizeof(a) / sizeof(int);

I'm newbie on this forum, however, I've already seen one interesting template to find a size of an array:

template <typename T, size_t N>
size_t sizeof_array( const T (&a) [ N ] ) {
    return N;
}

been posted by Duaos or Disch (can't resolve 'em).

As automatic arrays with a constant size are of different types for different sizes in C++, sizeof_array template instants different functions for arrays of different sizes received as arguments and returns the template parameter used to instant the function, and the parameter itself is a size of an array known by compiler!

This template is so cute (!) that I can't help recommend you to make use of one in your programs in the future instead of unsafe int size = sizeof(a) / sizeof(int);.

The other thing, one hardly could argue with Duaos, is you ought not to use system calls. All you need is to run your program under console.