C语言 如何在c中使用布尔函数
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how to work with boolean function in c
提问by Ravi
Anyone please tell me, what is wrong in this code
任何人请告诉我，这段代码有什么问题
#include<stdio.h>
bool func(char *,int);
void main()
{
char *a="Interview";
if(func(a,9))
{
printf("True");
}
else
{
printf("False");
}
}
bool func(char *s, int len)
{
if(len < 2)
return true;
else
return s[0] == s[len-1] && func(&s[1], len-2);
}
I believe this function always returns TRUE. This is an interview question. But, when I try to compile this, it shows 6 errors..
我相信这个函数总是返回TRUE. 这是一道面试题。但是，当我尝试编译它时，它显示了6 个错误..
回答by Mike
I'm going to guess it doesn't know what booland trueare. boolis not a primitive data type in C you need an extra include:
我要去猜它不知道什么是bool和true是。bool不是 C 中的原始数据类型，您需要额外的包括：
#include <stdbool.h>
The second part of your question? Does it always return TRUE?
你问题的第二部分？ Does it always return TRUE?
No:
When you come into the function you'll skip the first return because your length is 9. So instead you'll return if trueonly if:
否：当您进入该函数时，您将跳过第一个返回值，因为您的长度为 9。因此，true只有在以下情况下您才会返回：
return s[0] == s[len-1] && func(&s[1], len-2)
Is true. You can skip the recursive logic here because it's not modifying your string, just look at the first part:
是真的。您可以在这里跳过递归逻辑，因为它不会修改您的字符串，只需查看第一部分：
s[0] // this has to be 'I'
== // we need so what we compare against has to be 'I' as well
s[len-1] // This will be 'w'
So... that's not going to return true... who cares about ANDing (&&) the recursive part? I suspect the compiler will even optimize that out because everything here is hardcoded.
所以......这不会返回true......谁在乎ANDing（&&）递归部分？我怀疑编译器甚至会优化它，因为这里的所有内容都是硬编码的。
回答by md5
You just have to include the right header.
您只需要包含正确的标题。
#include <stdbool.h>
Or, you can use _Booltype, which don't need any inclusion. boolis just an alias from this type. By the way, don't forget to compile in C99.
或者，您可以使用_Bool不需要任何包含的类型。bool只是这种类型的别名。顺便说一句，不要忘记在 C99 中编译。
