数组查找[原因：为什么是“Hello World”; const char *？] [英] Array Lookup [Was: Why is "Hello World" const char* ?]
问题描述
您好，
感谢您对我签名/未签名字符的问题的回复。
问题是：我想要使用char数组进行ArrayLookup，所以
我需要将char转换为unsigned int。
但这不起作用！
如果我试试这个：
#include< stdio.h>
int main（）{
char c = -1; // 129无符号和-1签名吧？
//将数据转换为0到255之间的数组查找
unsigned int arrayIndex =（unsigned int）c;
if（arrayIndex< 0）
printf（" ArrayIndex在转换为unsigned int后仍然为负数
％d \ n"， arrayIndex）;
else
printf（"无符号表示对于ArrayIndex =％d \ n"，arrayIndex）;
}
输出为：ArrayIndex在转换为无符号后仍然为负值
int -1"
如何这可能吗？
我希望输出129.
谢谢！
Hans
Hello,
Thanks for all your response on my question about signed/unsigned chars.
The problem is this: I want to use the char array for a ArrayLookup, so
I need to convert char to unsigned int.
But this doesn''t work!
If I try this:
#include <stdio.h>
int main() {
char c = -1; // 129 unsigned and -1 signed right?
// convert it to a value between 0 - 255 for array Lookup
unsigned int arrayIndex = (unsigned int) c;
if (arrayIndex < 0)
printf("ArrayIndex still negative after conversion to unsigned int
%d\n",arrayIndex);
else
printf("Unsigned representation is OK for ArrayIndex=%d\n",arrayIndex);
}
The output is: "ArrayIndex still negative after conversion to unsigned
int -1"
How is this possible?
I would expect a output 129.
Thanks!
Hans
推荐答案
Hans写道：
Hans wrote:
你好，
感谢所有你的回答关于签名/未签名字符的问题。
问题是：我想使用char数组进行ArrayLookup，所以
我需要将char转换为unsigned int。
但这不起作用！
如果我试试这个：
#include< stdio.h> ;
int main（）{
char c = -1; // 129无符号和-1签名对吗？
错误。
//将数据转换为0到255之间的数组Lookup
unsigned int arrayIndex =（unsigned int）c;
不需要铸造。
这相当于
unsigned int arrayIndex = numeric_limits< unsigned int> :: max（）;
或UINT_MAX of< climits> ;.
if（b） arrayIndex< 0）
printf（ArrayIndex在转换为unsigned int后仍然为负数％
％d \ n，arrayIndex）;
printf（"无符号表示）可以用于ArrayIndex =％d \ n"，arrayIndex）;
}
输出为：ArrayIndex在转换为无符号后仍为负值
int -1
这怎么可能？
Hello,
Thanks for all your response on my question about signed/unsigned chars.
The problem is this: I want to use the char array for a ArrayLookup, so
I need to convert char to unsigned int.
But this doesn''t work!
If I try this:
#include <stdio.h>
int main() {
char c = -1; // 129 unsigned and -1 signed right?
Wrong.
// convert it to a value between 0 - 255 for array Lookup
unsigned int arrayIndex = (unsigned int) c;
The casting is not needed.
Also this is equivalent to
unsigned int arrayIndex = numeric_limits<unsigned int>::max();
or UINT_MAX of <climits>.
if (arrayIndex < 0)
printf("ArrayIndex still negative after conversion to unsigned int
%d\n",arrayIndex);
else
printf("Unsigned representation is OK for ArrayIndex=%d\n",arrayIndex);
}
The output is: "ArrayIndex still negative after conversion to unsigned
int -1"
How is this possible?
％d用于int，％u用于unsigned int。
我刚注意到你是交叉发布到clc，通常是一件坏事。
因为C和C ++是不同的语言。
无论如何你的程序修复并且是有效的C99和C ++ 03：
#include< stdio.h>
#include< limits.h>
int main（）
{
char c = -1;
unsigned int arrayIndex = c ;
if（arrayIndex< 0）
printf（转换为无符号后ArrayIndex仍为负数
int％u \ n，arrayIndex）;
else
printf（"无符号表示适用于
ArrayIndex =％u \ n \ nn"，arrayIndex）;
printf（UINT_MAX is％u\ n，UINT_MAX）;
}
-
Ioannis Vranos
http://www23.brinkster.com/ noicys
Hans写道：
Hans wrote:
输出结果为：< ArrayIndex在转换为无符号后仍然为负/> int -1"
这怎么可能？
The output is: "ArrayIndex still negative after conversion to unsigned
int -1"
How is this possible?
但是，原始的错误代码没有打印上面的内容。
-
Ioannis Vranos
http://www23.brinkster.com/noicys
Hans写道：
您好，
感谢您对我的签名/未签名字符问题的所有回复。
问题是：我想将char数组用于ArrayLookup，所以
我需要将char转换为unsigned int。
但这并不是'工作了！
如果我试试这个：
#include< stdio.h>
int main（）{
char c = - 1; // 129无符号和-1签名对吗？
错误。 c是-1或UCHAR_MAX（对于CHAR_BIT == 8：255）
//将其转换为0到255之间的值，用于数组Lookup
错误。您可以从以下获取UCHAR_MAX或UINT_MAX
unsigned int arrayIndex =（unsigned int）c;
可能你想要... =（unsigned char）c;
否则，演员阵容是不必要的。
if（arrayIndex< 0）
printf（ArrayIndex在转换为unsigned int后仍然为负数％
％d \ n，arrayIndex）;
％u;你在说谎类型，所以printf（）会弄错。 else
printf（"无符号表示对于ArrayIndex =％d \ n"，arrayIndex）;
Dito。输出结果为：转换为无符号后，ArrayIndex仍为负数
int -1"
你撒谎。上面的输出可能是
无符号表示可以用于ArrayIndex = -1 \ n
其他任何东西都是不可能的。
怎么样这可能吗？
不行。
我希望输出129.
我期望CHAR_BIT == 8 255或-1和固定的
printf（）格式字符串255或UINT_MAX可能是
2 ** 16-1或2 ** 32-1 （65，XXX或4，XXX，XXX，XXX）。
另见Ioannis Vranos的回复。
请决定是否以clc或clc ++发表。
F''up2 clc
谢谢！
Hello,
Thanks for all your response on my question about signed/unsigned chars.
The problem is this: I want to use the char array for a ArrayLookup, so
I need to convert char to unsigned int.
But this doesn''t work!
If I try this:
#include <stdio.h>
int main() {
char c = -1; // 129 unsigned and -1 signed right?
Wrong. c is either -1 or UCHAR_MAX (for CHAR_BIT==8: 255)
// convert it to a value between 0 - 255 for array Lookup
Wrong. You either get UCHAR_MAX or UINT_MAX from the following
unsigned int arrayIndex = (unsigned int) c;
Probably, you want to have ... = (unsigned char) c;
Otherwise, the cast is unnecessary.
if (arrayIndex < 0)
printf("ArrayIndex still negative after conversion to unsigned int
%d\n",arrayIndex); %u; you are lying about the type, so printf() will get it wrong. else
printf("Unsigned representation is OK for ArrayIndex=%d\n",arrayIndex); Dito. }
The output is: "ArrayIndex still negative after conversion to unsigned
int -1"
You are lying. The output of the above probably is
"Unsigned representation is OK for ArrayIndex=-1\n"
Anything else is not possible.
How is this possible?
It ain''t.
I would expect a output 129.
I would expect for CHAR_BIT==8 either 255 or -1 and for the fixed
printf() format string either 255 or UINT_MAX which is probably either
2**16-1 or 2**32-1 (65,XXX or 4,XXX,XXX,XXX).
See also the replies of Ioannis Vranos.
Please get decided whether to post in clc or clc++.
F''up2 clc
Thanks!
你是欢迎。
干杯
Michael
-
电子邮件：我的是/ at / gmx /点/地址。
You''re welcome.
Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.
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