如何切换和大小写字符串? [英] How to switch and case for string?

问题描述

我有以下代码

#define SWITCH(S) char *_S = S; if (0)
#define CASE(S) } else if (strcmp(_S, S) == 0) {switch(1) { case 1
#define BREAK }
#define DEFAULT } else {switch(1) { case 1

int main()
{
    char buf[256];

    printf("\nString - Enter your string: ");
    scanf ("%s", buf);

    SWITCH (buf) {
        CASE ("abcdef"):
            printf ("B1!\n");
            BREAK;
        CASE ("ghijkl"):
            printf ("C1!\n");
            BREAK;
        DEFAULT:
            printf ("D1!\n");
            BREAK;
    }
}

如果我使用 gcc -E 生成预处理器代码，我将获得以下代码

If I generate the pre-processor code with gcc -E, I will get the following code

int main()
{
    char buf[256];

    printf("\nString - Enter your string: ");
    scanf ("%s", buf);

    char *_S = buf;
    if (0) {
    } else if (strcmp(_S, "abcdef") == 0) {switch(1) { case 1:
        printf ("B1!\n");
        };
    } else if (strcmp(_S, "ghijkl") == 0) {switch(1) { case 1:
        printf ("C1!\n");
        };
    } else {switch(1) { case 1:
        printf ("D1!\n");
        };
    }
}

但是对于某些在代码中间定义 char * _S = buf; 的gcc而言，它不是狼来了，并且可能会提供编译错误

But for some gcc defining char *_S = buf; in the middle of the code is not wolcome and could provide compilation error

如何在宏中修复该问题?

How to fix that in my macro?

请不要建议将 char * _S 定义为全局(在 main 中)

Please do not suggest to define char *_S as global (out of the main)

推荐答案

哦，不！

我在不要使用它是非常可怕的，如果要避免if-else，可以在不折磨编译器的情况下进行操作，请考虑使用一对字符串:

Don't use it is very very horrific, if you want to avoid if-else you can do it without torturing the compiler, consider using pair of strings:

#include <stdio.h>
#include <string.h>

int main(void)
{
    char buf[256];
    const char *ap[] = {
        "abcdef", "B1!\n",
        "ghijkl", "C1!\n",
        NULL    , "D1!\n",
    }, **p = ap;

    printf("\nString - Enter your string: ");
    scanf ("%s", buf);
    while (*p) {
        if (strcmp(buf, *p) == 0) break;
        p += 2;
    }
    printf("%s", *(++p));
    return 0;
}

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