- #Operator to convert macro parameters to strings during preprocessing
- #The conversion of is completed in the preprocessing period, so it is only valid in the macro definition
- Compiler does not know the conversion function of ා
usage
#define STRING(x) #x printf("%s\n", STRING(Hello word));
Example analysis: basic usage of ා operator
#include <stdio.h> #define STRING(x) #x int main() { printf("%s\n", STRING(Hello word)); printf("%s\n", STRING(100)); printf("%s\n", STRING(while)); printf("%s\n", STRING(return)); }Output: Hello word 100 while return
Test_2.i
printf("%s\n", "Hello word"); printf("%s\n", "100"); printf("%s\n", "while"); printf("%s\n", "return");
Example analysis: the clever use of ා operator
Test_2.c
#include <stdio.h> #define CALL(f, p) (printf("Call funtion %s\n", #f), f(p)) int square(int n) { return n * n; } int func(int x) { return x; } int main() { int result = 0; result = CALL(square, 4); printf("result = %d\n", result); result = CALL(func, 10); printf("result = %d\n", result); return 0; }
Output: Call funtion square result = 16 Call funtion func result = 10
Test_2.i
result = (printf("Call funtion %s\n", "square"), square(4)); result = (printf("Call funtion %s\n", "func"), func(10));Operator operator
- ##Operator to bond two identifiers during preprocessing
- ##The connection function of is completed in the preprocessing period, so it is only valid in the macro definition
- Compiler does not know the connection function of ා
usage
#define CONNECT(a, b) a##b int CONNECT(a, 1); // int 1 a1 = 2;
Example analysis: basic usage of the ා operator
Test_3.c
#include <stdio.h> #define NAME(n) name##n int main() { int NAME(1); int NAME(2); NAME(1) = 1; NAME(2) = 2; printf("%d\n", NAME(1)); printf("%d\n", NAME(2)); }Output: 1 2
Test_3.i
int main() { int name1; int name2; name1 = 1; name2 = 2; printf("%d\n", name1); printf("%d\n", name2); }
Case analysis: engineering application of operators
Test_3.c
#include <stdio.h> #define STRUCT(type) typedef struct _tag_##type type;\ struct _tag_##type STRUCT(Student) { char* name; int id; }; int main() { Student s1; Student s2; s1.name = "s1"; s1.id = 1; s2.name = "s2"; s2.id = 2; printf("s1.name = %s\n", s1.name); printf("s1.id = %d\n", s1.id); printf("s2.name = %s\n", s2.name); printf("s2.id = %d\n", s2.id); return 0; }
Output: s1.name = s1 s1.id = 1 s2.name = s2 s2.id = 2
Test_4.i
typedef struct _tag_Student Student; struct _tag_Student { char* name; int id; };Summary
- #Operator to convert macro parameters to strings during preprocessing
- ##Operator to glue two identifiers during preprocessing
- Compiler does not know the existence of ා and ා - operators
- #And ා operators are only valid in macro definitions
The above contents refer to the series courses of Ditai Software Institute, please protect the original!