ARRAYS AS FUNCTION PARAMETERS

Please note that the material on this website is not intended to be exhaustive.
This is intended as a summary and supplementary material to the required textbook.

Using call by value is a very inefficient method of passing arrays as parameters to functions.   In C++, arrays are always passed as reference parameters.   Hence, there is no need to explicitly indicate the manner in which arrays are passed, i.e. with &, as you normally would need with single variables.  In the function declaration where the array is a parameter, the type referring to the array is followed by a pair of brackets, i.e. [ ].   In a function call, only the array–id is needed.   In the function definition heading where the array is a parameter, the array name is followed by a pair of empty brackets.

#define MaxDeg 9;
void main (void);

void main (void)
  {
    double Horners (double [ ], int , double); ¬ function declaration
    int deg;
    double fx, x;
    double Coef [MaxDeg + 1]; ¬ array declaration	
    ...
    fx = Horners (Coef, deg, x); ¬ function call
    return;
  }
		
double Horners (double c [ ], int d, double x) ¬ function definition	heading
  {
    double y;
    int i;
    y = 0;
    for ( i = d; i >= 0; i––)
      y = y * x + c [i];
    return (y);
  }
										  

When the array being passed as a parameter is a 2 dimensional array, attention has to be given to the way the array is stored in memory.   Although we think of a 2 dimensional array as consisting of rows and columns, it is actually linearly stored.   For example, if given the following:

It is actually contiguously stored in a linear fashion by rows:

Hence, the maximum value of the second dimension of the array must be specified in the function definition heading to insure proper access of data.

#define m ...
#define n ...

void main (void)
  {
    void Solve (float [ ][ ], int); ¬ function declaration
    double a [ m ][ n ];  ¬ array declaration	
    ...
    Solve (a, k); ¬ function call
    ...
    return;
  }
		
void Solve (float a [ ][ n ], int k) ¬ function definition heading
  {
    int i, j;
    ...
    for (i = 0; i <= k; i++)
      for (j = 0; j <= n; j++)
        a [ i ][ j ] = ...
    ...
    return;
  }
            

When passing multi–dimensional arrays as function parameters, the maximum values of all dimensions except the first must be specified in the function definition heading.

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© 1994-07-23 cpsm; last update 2005-01-23

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