C/Function/Function Parameters
Содержание
- 1 A function to increase your salary
- 2 Calculating an average using variable argument lists
- 3 Char pointer as the function parameter
- 4 Computes the area of three triangles
- 5 Define constant function parameter
- 6 Define int pointer parameter for a function
- 7 Demonstrate the use of pointers and parameter passing
- 8 Length of the function parameters
- 9 Pass Array into a function
- 10 Pass array value into function: by array, by empty array and by pointer
- 11 Pass array with different dimension into function
- 12 Pass char pointer into function
- 13 Pass double value into function
- 14 Passing parameter by pointer
- 15 Passing the data type addess into the function
- 16 Pass reference
- 17 Pass reference of an int value into function
- 18 Pass return value through function parameter
- 19 Pass value
- 20 Return value though parameter
- 21 Use function with pointer parameters
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>
