1. Arrays Part II Array Function Arguments
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Arrays Part II Array Function Arguments

2. Passing Arrays between Functions
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Passing Arrays between Functions
Sometimes we need to: 1. Pass an array to a function as input. 2. Pass an array to a function to modify. 3. Return an array from a function This does not work with what we now know! Instead: - declare an array in the invoking function - pass it to the invoked function using #2.

3. Passing Arrays between Functions
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Passing Arrays between Functions
C/C++ never passes arrays By Value! If it did, a COPY of the entire array would have to be made each time the function is invoked. This is so inefficient, it simply is not done!

4. Syntax: Array as a Formal Argument
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Syntax: Array as a Formal Argument
Function Declaration Syntax:
returnType funcName ( type ident [ ] ) { }
Place a pair of square brackets with nothing between after the identifier (name of the array argument).
Never use the & with an array...it is already PBR

5. Syntax: Array as an Actual Argument
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Syntax: Array as an Actual Argument
Function Invocation Syntax: {
type id [size]; // array declaration
...
funcName(id); // invocation }
Use only the local name of the array...no need for any brackets.

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Semantics
Arrays are always PBR, so the Formal Argument simply renames the Actual Argument upon invocation.

7. Semantics Example: const int SIZE = 5; void init(int a[]) {
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Semantics
Example:
const int SIZE = 5;
void init(int a[]) {
for (int i=0; i<SIZE; i++)
a[i] = 0; }
int main() {
int b[5];
init(b);

8. Semantics Example: const int SIZE = 5; void init(int a[]) {
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Semantics
Example:
const int SIZE = 5;
void init(int a[]) {
for (int i=0; i<SIZE; i++)
a[i] = 0; }
int main() {
int b[5];
init(b);

9. Semantics Example: a simply renames b const int SIZE = 5;
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Semantics
Example: a simply renames b
const int SIZE = 5;
void init(int a[]) {
for (int i=0; i<SIZE; i++)
a[i] = 0; }
int main() {
int b[5];
init(b);

10. Semantics Example: const int SIZE = 5; void init(int a[]) {
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Semantics
Example:
const int SIZE = 5;
void init(int a[]) {
for (int i=0; i<SIZE; i++)
a[i] = 0; }
int main() {
int b[5];
init(b);

11. Semantics Example: const int SIZE = 5; void init(int a[]) {
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Semantics
Example:
const int SIZE = 5;
void init(int a[]) {
for (int i=0; i<SIZE; i++)
a[i] = 0; }
int main() {
int b[5];
init(b);

12. Common Functions Initialize // initialize ALL elements to 0
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Common Functions
Initialize
// initialize ALL elements to 0
const int MAX = 100;
void init(double a[], int & num) {
for (int i=0; i < MAX; i++) {
a[i] = 0.0;
num = 0; }

13. Common Functions Populate (User Input) // ask the user to enter values
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Common Functions
Populate (User Input)
// ask the user to enter values
void askUserPopulate(double a[], int num) {
for (int i=0; i < num; i++) {
cout << "Enter a value: ";
cin >> a[i]; }

14. Common Functions Sum // return the sum of the values in the array
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Common Functions
Sum
// return the sum of the values in the array
double sum(double a[], int num) {
double sum = 0.0;
for (int i=0; i < num; i++) {
sum += a[i]; }

15. Common Functions Max // return the highest value in the array
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Common Functions
Max
// return the highest value in the array
double max(double a[], int num) {
double m = a[0]; // start with first ele
for (int i=1; i < num; i++) {
if (a[i] > m)
m = a[i]; }
return m;

16. Common Functions Min // return the lowest number in the array
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Common Functions
Min
// return the lowest number in the array
double min(double a[], int num) {
double m = a[0]; // start with first ele
for (int i=1; i < num; i++) {
if (a[i] < m)
m = a[i]; }
return m;

17. Common Functions Print // print all the values on one line
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Common Functions
Print
// print all the values on one line
void print(double a[], int num) {
for (int i=0; i < num; i++) {
cout << a[i] << ” ”; }
cout << endl;

18. Append to a Partial Array
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Common Functions
Append to a Partial Array
// append new value to array, if enough room
void append(double a[], int n, double newVal) {
if (num < MAX) {// check if room available
a[num] = newValue;
num ++; }
// else array is full, can not append

19. Remove from Partial Array
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Common Functions
Remove from Partial Array

20. Remove from a Partial Array
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Common Functions
Remove from a Partial Array
// remove r’th ele from the array and return it
double remove(double a[], int n, int r) {
double rem=0.0; // some invalid/empty value
if (r>=0 && r<num) { // ensure r "in range"
rem = a[r]; // save a copy
num--; // one less item in list
for (int i = r; i < num; i++)
a[i] = a[i+1];
a[num] = EMPTY_VALUE; // optional }
// else r is out of range, can't remove
return rem;

21. Common Functions Linear Search
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Common Functions
Linear Search
// find INDEX where srchVal found; -1=not found
int search(double a[], int num, double srchVal){
int found = -1; // assume not found
for (int i=0; i<num; i++) {
if (a[i] == s) // found it!
found = i; // remember WHERE found }
return found;

22. (Easy to Memorize) Bubble Sort
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Common Functions
(Easy to Memorize) Bubble Sort
void sort(double a[], int num) {
for (int i=0; i<num-1; i++) {
for (int j=i+1; j<num; j++)
if (a[i] > a[j]) { // low to hi
// swap a[i] with a[j]
double t = a[i];
a[i] = a[j];
a[j] = t; }

23. (Easy to Memorize) Bubble Sort
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Common Functions
(Easy to Memorize) Bubble Sort
void sort(double a[], int num) {
for (int i=0; i<num-1; i++) {
for (int j=i+1; j<num; j++)
if (a[i] < a[j]) { // hi to low
// swap a[i] with a[j]
double t = a[i];
a[i] = a[j];
a[j] = t; }

24. Vocabulary See Vocabulary at the end of the First Set of Slides
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Vocabulary
See Vocabulary
at the end of the
First Set of Slides
on Arrays