array1.cpp

Code

/*
    array1.cpp
    CIS 250
    David Klick
    2005-02-06

    Demonstration of arrays, passing arrays to functions,
    and pointer arithmetic.
*/

#include <iostream>
using std::cout;
using std::endl;

float sumArray1(float a[], int len);
float sumArray2(float* a, int len);
void initArray(float* a, int len);
void clearArray(float*, int);
void displayArray(int n[], int len);

int main(void) {
    float x[15];   // declares and creates array of 15 floats
    // initialize an array when it is declared
    int x2[] = { 10, 8, 6, 4, 2, 0 };

    // you can pass arrays to functions by using the array's name
    // - its equivalent to a pointer to the first array element
    // - you also have to send the size of the array
    cout << "Array x2: ";
    displayArray(x2, 6);

    float sum = sumArray1(x, 15);

    // don't forget to initialize your elements
    cout << "Sum of new array (uninitialized): " << sum << endl;

    // the functions can use pointers and work just as well
    clearArray(&x[0], 15);
    sum = sumArray2(x, 15);
    cout << "Sum of array after clearing: " << sum << endl;

    // since arrays are sent to functions by reference,
    //    changes the functions make to the array are not made
    //    to a copy, but the actual array and will not be lost
    initArray(x, 15);

    sum = sumArray2(x, 15);
    cout << "Sum of array after initArray: " << sum << endl;

    return 0;
}

float sumArray1(float arr[], int len) {
    float sum = 0.0f;
    for (int i=0; i<len; i++) sum += arr[i];
    return sum;
}

float sumArray2(float* arr, int len) {
    float sum = 0.0f;
    for (int i=0; i<len; i++) sum += *(arr+i);
    return sum;
}

void initArray(float arr[], int len) {
    // this loop sets the array to 0.0, 1.1, 2.2, ...
    for (int i=0; i<len; i++) {
        *(arr+i) = i * 1.1f;
    }
}

void clearArray(float* n, int len) {
    while (--len >= 0) n[len] = 0.0f;
}

void displayArray(int* n, int len) {
    for (int i=0; i<len; i++) {
        cout << (i>0 ? ", " : "") << n[i];
    }
    cout << endl;
}