C -- number of elements in an array?

Question

Suppose that I have the following c function:

int MyFunction( const float arr[] )
{
    // define a variable to hold the number of items in 'arr'
    int numItems = ...;

    // do something here, then return...

    return 1

}

How can I get into numItems the number of items that are in the array arr?

Answer 1

Unfortunately you can't get it. In C, the following 2 are equivalent declarations.

int MyFunction( const float arr[] );
int MyFunction( const float* arr );

You must pass the size on your own.

int MyFunction( const float* arr, int nSize );

In case of char pointers designating strings the length of the char array is determined by delimiter '\0'.

Answer 2

Either you pass the number of elements in another argument or you have some convention on a delimiting element in the array.