学习自狄泰软件学院唐佐林老师C语言课程,文章中图片取自老师的PPT,仅用于个人笔记。
实验1 :#运算符分使用
25-1.c
#include <stdio.h>
#define STRING(x) #x
int main()
{
printf("%s\n", STRING(Hello world!));
printf("%s\n", STRING(100));
printf("%s\n", STRING(while));
printf("%s\n", STRING(return));
return 0;
}
gcc -E 25-1.c -o 25-1.i
单步编译,看预处理结果,此处提前删除 包含的库头文件
# 1 "25-1.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "25-1.c"
int main()
{
printf("%s\n", "Hello world!");
printf("%s\n", "100");
printf("%s\n", "while");
printf("%s\n", "return");
return 0;
}
. 编译运行
mhr@ubuntu:~/work/C$ gcc 25-1.c
mhr@ubuntu:~/work/C$ ./a.out
Hello world!
100
while
return
mhr@ubuntu:~/work/C$
实验2:#运算符分使用2
#include <stdio.h>
// 使用 逗号表达式 以及 #操作符 组合
#define CALL(f, p) (printf("Call function %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;
}
gcc -E 25-2.c -o 25-2.i
单步编译,看预处理结果,此处提前删除 包含的库头文件
# 1 "25-2.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "25-2.c"
int square(int n)
{
return n * n;
}
int func(int x)
{
return x;
}
int main()
{
int result = 0;
result = (printf("Call function %s\n", "square"), square(4));
printf("result = %d\n", result);
result = (printf("Call function %s\n", "func"), func(10));
printf("result = %d\n", result);
return 0;
}
编译运行
mhr@ubuntu:~/work/C$ gcc 25-2.c
mhr@ubuntu:~/work/C$
mhr@ubuntu:~/work/C$
mhr@ubuntu:~/work/C$ ./a.out
Call function square
result = 16
Call function func
result = 10
mhr@ubuntu:~/work/C$
mhr@ubuntu:~/work/C$
实验3: ## 操作符使用学习
#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));
return 0;
}
gcc -E 25-3.c -o 25-3.i
单步编译,看预处理结果,此处提前删除 包含的库头文件
# 1 "25-3.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "25-3.c"
int main()
{
int name1;
int name2;
name1 = 1;
name2 = 2;
printf("%d\n", name1);
printf("%d\n", name2);
return 0;
}
编译运行
mhr@ubuntu:~/work/C$ gcc 25-3.c
mhr@ubuntu:~/work/C$ ./a.out
1
2
mhr@ubuntu:~/work/C$
实验4:##操作符实际使用
在工程中,有成千上万个结构体需要定义,但是每一次定义结构体变量的时候都要写 struct xxx xxx 很麻烦,可以用 typedef + ##操作符 组合使用 简化工程中 结构体的定义
#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 = 0;
s2.name = "s2";
s2.id = 1;
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;
}
gcc -E 25-4.c -o 25-4.i
单步编译,看预处理结果,此处提前删除 包含的库头文件
# 1 "25-4.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "25-4.c"
typedef struct _tag_Student Student; struct _tag_Student
{
char* name;
int id;
};
int main()
{
Student s1;
Student s2;
s1.name = "s1";
s1.id = 0;
s2.name = "s2";
s2.id = 1;
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;
}
编译运行
mhr@ubuntu:~/work/C$
mhr@ubuntu:~/work/C$ gcc 25-4.c
mhr@ubuntu:~/work/C$
mhr@ubuntu:~/work/C$ ./a.out
s1.name = s1
s1.id = 0
s2.name = s2
s2.id = 1
mhr@ubuntu:~/work/C$