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Interesting way of how we can use macros, to define function (bodies) having a generic code. To understand whats happening, look at the pre-processor output using "-E" flag
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| // simple swapping without data types | |
| #include <stdio.h> | |
| #define SWAP(x, y) \ | |
| tmp2 = *x; \ | |
| *x = *y; \ | |
| *y = tmp2; | |
| #define DEFINE_SWAP(FUN_SWAP, T) \ | |
| void FUN_SWAP(T *x, T *y) { \ | |
| T tmp = *x; \ | |
| *x = *y; \ | |
| *y = tmp; \ | |
| } | |
| static void funSwapInt(int *a, int *b); | |
| static void funSwapFloat(float *a, float *b); | |
| // generic swap function using macro | |
| DEFINE_SWAP(funSwapInt, int); | |
| DEFINE_SWAP(funSwapFloat, float); | |
| int main() { | |
| int a = 5; | |
| int b = 10; | |
| int tmp2; | |
| printf("a = %d , b = %d \n", a, b); | |
| // during pre-processing, the whole DEFINE_SWAP block will be replaced here | |
| SWAP(&a, &b); | |
| printf("a = %d , b = %d \n", a, b); | |
| funSwapInt(&a, &b); | |
| printf("a = %d , b = %d \n", a, b); | |
| float fa = 1.0, fb = 5.0; | |
| printf("fa = %f , fb = %f \n", fa, fb); | |
| funSwapFloat(&fa, &fb); | |
| printf("fa = %f , fb = %f \n", fa, fb); | |
| } | |
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