使用最大值初始化int和char [英] Initialize int and char with maximum values
问题描述
我想用最大值
值初始化unsigned int和unsigned char。
只是为了确定：
unsigned int i = pow（256，sizeof（i）） - 1;
unsigned char c = pow（256，sizeof（c）） - 1;
一直有效吗？
谢谢，
Matthias
-
$ b $bFür电子邮件Anweisung in der Adresse befolgen
I want to initialize unsigned int and unsigned char with their maximum
value.
Just for being sure: Does
unsigned int i = pow(256,sizeof(i))-1;
unsigned char c = pow(256,sizeof(c))-1;
always work?
Thanks,
Matthias
--
Für emails Anweisung in der Adresse befolgen
推荐答案
Der Andere写道：
Der Andere wrote:
我想初始化unsigned int和unsigned char及其最大值
。
只是为了确定：
unsigned int i = pow（256，sizeof（i）） - 1;
unsigned char c = pow（256，sizeof（c）） - 1 ;
总是有效吗？
I want to initialize unsigned int and unsigned char with their maximum
value.
Just for being sure: Does
unsigned int i = pow(256,sizeof(i))-1;
unsigned char c = pow(256,sizeof(c))-1;
always work?
请改用std :: numeric_limits类：
#include< limits> ;
int main（）
{
unsigned char c = std :: numeric_limits< unsigned char> :: max（ ）;
unsigned int i = std :: numeric_limits< unsigned int> :: max（）;
返回0;
}
-
Peter van Merkerk
peter.van.merkerk（at）dse.nl
Use the std::numeric_limits class instead:
#include <limits>
int main()
{
unsigned char c = std::numeric_limits<unsigned char>::max();
unsigned int i = std::numeric_limits<unsigned int>::max();
return 0;
}
--
Peter van Merkerk
peter.van.merkerk(at)dse.nl
> >我想用最大的
> > I want to initialize unsigned int and unsigned char with their maximum
值来初始化unsigned int和unsigned char。
只是为了确定：
unsigned int i = pow（ 256，sizeof（i）） - 1;
unsigned char c = pow（256，sizeof（c）） - 1;
始终有效吗？
value.
Just for being sure: Does
unsigned int i = pow(256,sizeof(i))-1;
unsigned char c = pow(256,sizeof(c))-1;
always work?
使用而是std :: numeric_limits类：
#include< limits>
int main（）
{
unsigned char c = std :: numeric_limits< unsigned char> :: max（）;
unsigned int i = std :: numeric_limits< unsigned int> :: max（）;
return 0;
}
Use the std::numeric_limits class instead:
#include <limits>
int main()
{
unsigned char c = std::numeric_limits<unsigned char>::max();
unsigned int i = std::numeric_limits<unsigned int>::max();
return 0;
}
谢谢！
问候，
Matthias
Thanks!
Regards,
Matthias
2004年4月21日星期三，Der Andere写道：
On Wed, 21 Apr 2004, Der Andere wrote:
我想用
最大值初始化unsigned int和unsigned char。
只是为了确定：
unsigned int i = pow（256，sizeof（i）） - 1;
unsigned char c = pow（256，sizeof（c）） - 1; <总是有效吗？
I want to initialize unsigned int and unsigned char with their maximumvalue.
Just for being sure: Does
unsigned int i = pow(256,sizeof(i))-1;
unsigned char c = pow(256,sizeof(c))-1;
always work?
sizeof的单位是一个炭的大小。一个char在一个实现中可以有超过8个
位。所以不，你的解决方案不能保证
工作。相反，使用：
#include< limits>
int main（）
{
unsigned int i = std :: numeric_limits< unsigned int> :: max（）;
unsigned char c = std :: numeric_limits< unsigned char> :: max（）;
返回0;
}
丑陋且不安全（？）替代方案：
int main（）
{
unsigned int i = static_cast< unsigned int>（ - 1）;
unsigned char c = static_cast< ; unsigned char>（ - 1）;
}
这可能不起作用的原因是它假定二元补充
签名整数的表示。
干杯，
克劳迪奥。
-
Claudio Jolowicz
http：//www.doc.ic。 ac.uk/~cj603
http://www.parashift.com/c++-faq-lit...sic-types.html
The unit of sizeof is the size of a char. A char can have more than 8
bits in an implementation. So no, your solution is not guaranteed to
work. Instead, use:
#include <limits>
int main()
{
unsigned int i = std::numeric_limits<unsigned int>::max();
unsigned char c = std::numeric_limits<unsigned char>::max();
return 0;
}
An ugly and unsafe (?) alternative:
int main()
{
unsigned int i = static_cast<unsigned int>(-1);
unsigned char c = static_cast<unsigned char>(-1);
}
The reason this might not work is that it assumes twos complement
representation of signed integers.
Cheers,
Claudio.
--
Claudio Jolowicz
http://www.doc.ic.ac.uk/~cj603
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