英文:
How to use tolower or toupper with a special character such as Å
问题
在使用C语言编程时，我遇到了关于tolower和toupper函数的问题。
我想要打印一个大写字母 'Å'，然后使用tolower函数打印一个小写字母 'å'。
首先，我声明一个变量 int x，并给它赋值为 143（因为在ASCII中，'Å' 对应该整数）。然后，我使用 printf("%c", x) 打印出 x，我将得到一个 'Å'。我还想要打印一个 'å'（小写的 'Å'），为此我使用了 tolower 函数。然而，我并没有得到 'å'，而是得到了两个 'Å'，我不明白为什么会这样。如果有人能够解释给我，我将不胜感激。另外，我是编程新手，因此可能不时使用不正确的术语，但希望你能理解！
以下是我的代码：
#include <stdio.h>
#include <ctype.h>
int main(void){
int x = 143;
printf("大写是 %c\n", x);
printf("小写是 %c\n", tolower(x));
return 0;
}
输出：
大写是 Å
小写是 Å
我也尝试过以下代码，但输出结果相同：
#include <stdio.h>
#include <ctype.h>
int main(void){
int x = 143;
int y;
y = tolower(x);
printf("大写是 %c\n", x);
printf("小写是 %c\n", y);
return 0;
}
英文:
While programming in C, I encountered a problem regarding the tolower and toupper functions.
I want to print an upper case 'Å', and then using the tolower function to print a lower case 'Å' ('å').
First, I declare a variable int x, and give it a value of 143 (because in the ASCII, Å is given that integer). When I then print out x using printf("%c", x) I will get an 'Å'. I also want to print an 'å' (a lower case Å), and to do so, I used the tolower function. However, I do not get an 'å', I only get 2 Å's and I do not understand why. If someone could explain it to me I will be grateful. Also, I am new to programming. Thus I might not use the correct terms at all times, but hopefully you will understand!
Here is my code:
#include <stdio.h>
#include <ctype.h>
int main(void){
int x = 143;
printf("Upper case is %c\n", x);
printf("Lower case is %c\n", tolower(x));
return 0;
}
Output:
Upper case is Å
Lower case is Å
I also tried this, but the output was the same:
#include <stdio.h>
#include <ctype.h>
int main(void){
int x = 143;
int y;
y = tolower(x);
printf("Upper case is %c\n", x);
printf("Lower case is %c\n", y);
return 0;
}
答案1
得分: 2
请看：tolower
返回值
ch的小写版本，如果在当前C语言环境中没有列出小写版本，则返回未修改的ch。
由于你得到了未修改的值，这意味着在当前C语言环境中找不到小写版本。
为了解决这个问题，一个解决方案可能是通过setlocale设置适当的C语言环境。
此外，我建议阅读以下两篇文章，因为值143不是ASCII而是扩展ASCII（并且以便更好地理解setlocale的用途）：
英文:
Have a look at: tolower
> Return value
>
> Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale.
Since you get the unmodified value, that means no lowercase version was found.
To fix the problem, a solution might be to set the appropriate C locale (via setlocale).
Furthermore, i would suggest to read the following two articles, since the value 143 is not ASCII but Extended ASCII (and to get a better understanding what setlocale is good for):
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