в 14:20, 25 мая 2010

2010-05-25T14:20:56Z

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2010-05-25T10:22:34Z

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==A function to increase your salary==

<source lang="cpp">
#include <stdio.h>
long *IncomePlus(long* pValue); /* function Prototype */
int main() {
long your_value = 30L;
long *pold_value = &your_value;
long *pnew_value = NULL;
pnew_value = IncomePlus( pold_value );
printf("\n Old value = $%d", *pold_value);
printf(" New value = $%d\n", *pnew_value);
}

long *IncomePlus(long *pValue)
{
*pValue += 10L;
return pValue;
}

</source>

== Calculating an average using variable argument lists==

<source lang="cpp">
#include <stdio.h>
#include <stdarg.h>
double average(double v1 , double v2,...);
int main()
{
printf("\n Average = %lf", average(3.5, 4.5, 0.0));
printf("\n Average = %lf", average(1.0, 2.0));
printf("\n Average = %lf\n", average(0.0,1.2,1.5));
}
double average( double v1, double v2,...)
{
va_list parg;
double sum = v1+v2;
double value = 0;
int count = 2;
va_start(parg,v2);
while((value = va_arg(parg, double)) != 0.0)
{
sum += value;
printf("\n in averge = %.2lf", value);
count++;
}
va_end(parg); /* End variable argument process */
return sum/count;
}

</source>

==Char pointer as the function parameter==

<source lang="cpp">

#include <stdio.h>
void f(char *p);
int main(void)
{
f("this is a test");
return 0;
}
void f(char *p)
{
while(*p) { /* loop as long as p does not point to the
null which is the string terminator*/
printf("%c", *p);
p++; /* go to next character */
}
printf("\n");
}

</source>

==Computes the area of three triangles==

<source lang="cpp">
#include <stdio.h>
float triangle(float width, float height)
{
float area;
area = width * height / 2.0;
return (area);
}
int main()
{
printf("Triangle #1 %f\n", triangle(1.3, 8.3));
printf("Triangle #2 %f\n", triangle(4.8, 9.8));
printf("Triangle #3 %f\n", triangle(1.2, 2.0));
return (0);
}

</source>

==Define constant function parameter ==

<source lang="cpp">
#include <stdio.h>
void print_str(const char *p);
int main(void)
{
char str[80];
printf("Enter a string: ");
gets(str);
print_str(str);
return 0;
}
void print_str(const char *p)
{
while(*p)
putchar(*p++);
}

</source>

==Define int pointer parameter for a function==

<source lang="cpp">
#include <stdio.h>
void f(int *k);
main () {
int i;
i = 0;

printf (" i before call %d \n", i);

f(&i);

printf (" i after call %d \n", i);
}
void f(int *k)
{
*k = *k + 10;
}

</source>

==Demonstrate the use of pointers and parameter passing==

<source lang="cpp">
#include <stdio.h>
void inc_count(int *count_ptr)
{
++(*count_ptr);
}
int main()
{
int count = 0;
while (count < 10){
inc_count(&count);
}
return (0);
}

</source>

==Length of the function parameters==

<source lang="cpp">
#include <stdio.h>
#include <stdarg.h>
void print_message(char *format, ...);
int main(void)
{
print_message("Cannot open file %s.", "test");
return 0;
}
void print_message(char *format, ...)
{
va_list ptr; /* get an arg ptr */
/* initialize ptr to point to the first argument after the
format string
*/
va_start(ptr, format);
/* print out message */
vprintf(format, ptr);
va_end(ptr);
}

</source>

==Pass Array into a function ==

<source lang="cpp">

#include <stdio.h>
void printarr(int a[]) {
int i;
for(i = 0;i<5;i++) {
printf(" %d\n",a[i]);
}
}
main() {
int a[5];
int i;

for(i = 0;i<5;i++) {
a[i]=i;
}
printarr(a);
}

</source>

==Pass array value into function: by array, by empty array and by pointer==

<source lang="cpp">

#include <stdio.h>
void f1(int num[5]), f2(int num[]), f3(int *num);
int main(void)
{
int count[5] = {1, 2, 3, 4, 5};
f1(count);
f2(count);
f3(count);
return 0;
}
/* parameter specified as array */
void f1(int num[5])
{
int i;
for( i = 0; i < 5; i++)
printf("%d ", num[ i ]);
}
/* parameter specified as unsized array */
void f2(int num[])
{
int i;
for( i = 0; i < 5; i++)
printf("%d ", num[ i ]);
}
/* parameter specified as pointer */
void f3(int *num)
{
int i;
for(i = 0; i < 5; i++)
printf("%d ", num[ i ]);
}

</source>

==Pass array with different dimension into function==

<source lang="cpp">
#include <stdio.h>
void print_onedim(int a[]);
void print_twodim(int a[][4]);
void print_threedim(int a[][3][4]);
main() {
int cnt=0;
int a[2][3][4];
int i;
int j;
int k;
for(i = 0;i < 2; i++){
for(j = 0;j < 3; j++){
for(k = 0;k < 4; k++) {
a[i][j][k] = cnt;
cnt++;
}
}
}
print_onedim(a[1][1]);
print_twodim(a[1]);
print_threedim(a);
}
void print_onedim(int a[]) {
int i;
for(i = 0; i < 4 ; i++)
printf("%d ", a[i]);
}
void print_twodim(int a[][4]) {
int j;
for(j = 0;j < 3; j++)
print_onedim(a[j]);
printf("\n");
}
void print_threedim(int a[][3][4]) {
int j;
printf("Each two dimension matrix\n");
for(j = 0; j < 2 ; j++)
print_twodim( a [ j ] );
}

</source>

==Pass char pointer into function==

<source lang="cpp">
#include <stdio.h>
void print_vertical(char *str); /* prototype */
int main(int argc, char *argv[])
{
if(argc > 1) print_vertical(argv[1]);
return 0;
}
void print_vertical(char *str)
{
while(*str)
printf("%c\n", *str++);
}

</source>

==Pass double value into function==

<source lang="cpp">

#include <stdio.h>
double feet_to_meter(double f);
int main(void)
{
double feet;
printf("Enter feet: ");
scanf("%lf", &feet);
printf("Meters: %f", feet_to_meter(feet));
return 0;
}
double feet_to_meter(double f)
{
return f / 3.28;
}

</source>

==Passing parameter by pointer==

<source lang="cpp">

#include <stdio.h>
void prompt(char *msg, int *num);
int main(void)
{
int i;
prompt("Enter a num: ", &i);
printf("Your number is: %d", i);
return 0;
}
void prompt(char *msg, int *num)
{
printf(msg);
scanf("%d", num);
}

</source>

==Passing the data type addess into the function==

<source lang="cpp">
#include <stdio.h>
void swap(int *x, int *y);
int main(void)
{
int i, j;
i = 10;
j = 20;
printf("i and j before swapping: %d %d\n", i, j);
swap(&i, &j); /* pass the addresses of i and j */
printf("i and j after swapping: %d %d\n", i, j);
return 0;
}
void swap(int *x, int *y)
{
int temp;
temp = *x; /* save the value at address x */
*x = *y; /* put y into x */
*y = temp; /* put x into y */
}

</source>

==Pass reference==

<source lang="cpp">
#include <stdio.h>
int change(int* pnumber); /* Function prototype */
void main()
{
int number = 20;
int* pnumber = &number;
int result = 0;
result = change(pnumber);
printf("\nIn main, result = %d\tnumber = %d", result, number);
}
int change(int* pnumber)
{
*pnumber *= 2;
printf("\n In function change, *pnumber = %d\n", *pnumber );
return *pnumber;
}

</source>

==Pass reference of an int value into function==

<source lang="cpp">
#include <stdio.h>
void f(int *k) {
*k = *k + 10;
}
main ( ) {
int i;
i = 0;

printf ("The value of i before call %d \n", i);

f(&i);

printf ("The value of i after call %d \n", i);
}

</source>

==Pass return value through function parameter==

<source lang="cpp">
#include <stdio.h>
#include <stdlib.h>

void mean(int a,int b, int *ptr_to_answer) {
*ptr_to_answer = (a + b)/2;
}
int main() {
int i, j;
int answer;
i = 6;
j = 9;
mean(i,j, &answer); /* passing a pointer to "answer" */

printf(" The mean of %d and %d = %d\n", i, j, answer);
}

</source>

==Pass value==

<source lang="cpp">

#include <stdio.h>
int change(int number);
void main()
{
int number = 20;
int result = 12;
result = change(number);
printf("\n In main, result = %d \t number = %d", result, number);
}

int change(int number) {
number = 2 * number;
printf("\n In function change, number = %d\n", number);
return number;
}

</source>

==Return value though parameter==

<source lang="cpp">
#include <stdio.h>
#include <stdlib.h>
void mean(int a, int b, int return_val ) {
return_val = (a + b) / 2;
printf("return_val in mean in %d\n",return_val);
}
int main() {
int i, j;
int answer;
i = 7;
j = 9;
mean(i, j, answer);
printf("The mean of %d and %d = %d\n", i, j, answer);
}

</source>

==Use function with pointer parameters==

<source lang="cpp">
void f(int *k) {
*k = *k + 10;
}

int main () {
int i = 0;

printf (" i before call %d \n", i);
f(&i);
printf (" i after call %d \n", i);
}

</source>

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