C/Macro Preprocessor/Macro Function — различия между версиями
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Текущая версия на 10:23, 25 мая 2010
Содержание
- 1 Define Macro as simple function
- 2 Define small function in macro
- 3 Defining a macro to compare two values
- 4 Defining a macro to output the value of an expression
- 5 Generate a square table
- 6 Make string
- 7 Use Macro to check the int range
- 8 Use macro to find the minor variable
- 9 Use Macro to get the bigger int value
- 10 Use marco for small function
Define Macro as simple function
#include <stdio.h>
#define SUM(i, j) ((i)+(j))
int main(void)
{
int sum;
sum = SUM(10, 20);
printf("%d", sum);
return 0;
}
Define small function in macro
#define CUBE(x) x*x*x
#include <stdio.h>
main () {
int k = 5;
int j = 0;
j = CUBE(k); // j = k*k*k
printf ("Cube value of j is %d\n", j);
}
Defining a macro to compare two values
/*
The macro function can work with numerical values
of any type. The values can be variables, constants or expressions.
*/
#include <stdio.h>
#define COMPARE(x,y) ((x)<(y)?-1:((x)==(y)?0:1))
int main()
{
double a = 1.5;
int n = 2;
float z = 1.1f;
printf("\n compare %lf (double) with %f (float): %d", a , z, COMPARE(a,z));
printf("\n compare %lf (double) with %d (int): %d", a , n, COMPARE(a,n));
printf("\n compare %d (int) with %f (float): %d", n , z, COMPARE(n,z));
printf("\n compare \" n * a\" = %lf \n"
" with \"n+1\" = to %d (double): %d",
n*a , n+1, COMPARE(n*a,n+1));
printf("\n");
}
Defining a macro to output the value of an expression
#include <stdio.h>
#define print_value(expr) printf("\n" #expr " = %lf", (double)expr);
void main() {
int n = 10;
double f = 6.5;
print_value( n );
print_value( f );
printf("\n");
print_value(f * f + 4.0);
print_value( n / 2 + 3);
print_value( 3 * 4 + 12 / 2 - 8);
printf("\n");
}
Generate a square table
#include <stdio.h>
#define SQR(x) ((x) * (x))
int main()
{
int counter = 0;
while (counter < 5)
printf("x %d square %d\n", counter, SQR(++counter));
return (0);
}
Make string
#include <stdio.h>
#define mkstr(s) # s
int main(void)
{
printf(mkstr(I like C));
return 0;
}
Use Macro to check the int range
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#define RANGE(i, min, max) (i < min) || (i > max) ? 1 : 0
int main(void)
{
int r;
/* random numbers between 1 and 100 */
do {
do {
r = rand();
} while(RANGE(r, 1, 100));
printf("%d ", r);
} while(!kbhit());
return 0;
}
Use macro to find the minor variable
#include <stdio.h>
#define min(a, b) ((a<b) ? a : b )
int main() {
int a,b,c;
a = 1;
b = 2;
c = min ( a, b);
printf ( "a: %d, b: %d, c: %d\n", a, b, c );
}
Use Macro to get the bigger int value
#include <stdio.h>
#define MAX(i, j) i>j ? i : j
int main(void)
{
printf("%d\n", MAX(3, 2));
printf("%d\n", MAX(1, -1));
/* this statement does not work correctly */
printf("%d\n", MAX(100 && -1, 0));
return 0;
}
Use marco for small function
#include <stdio.h>
#define ABS(a) (a) < 0 ? -(a) : (a)
int main(void)
{
printf("abs of -1 and 1: %d %d", ABS(-1), ABS(1));
return 0;
}