Exercise 4.14 - swap that interchanges two arguments of type t#
Question#
Define a macro swap(t,x,y) that interchanges two arguments of type t.
/* a macro swap(t,x,y) that interchanges two arguments of type t */
#include<stdio.h>
#define swap(t,x,y) { t _z; \
_z = x;\
x = y;\
y = _z; }
int main(void)
{
char x,y;
x='a';
y='b';
printf("x= %c \t y= %c\n",x,y);
swap(char,x,y);
printf("x=%c \t y=%c\n",x,y);
}
Explanation#
There are two types of macros in C namely object-like and function-like. In object type, we do substitution and in function macros we can send a variable as argument. In this program we are going to use function-like macro to swap.
We do this by defining macro:
#define swap(t,x,y) { t _z; \
_z = x;\
x = y;\
y = _z; }
In the macro, we send type t as an argument and two variables x and y to swap. We create a temperorary variable called _z of type t and use it to swap x and y.