我目前正在为我的CS课程做作业。我正在尝试打印 int、short 和 long 数据类型的最大和最小有符号数。
我不完全确定该怎么做。我一直在使用 sizeof() 函数来确定每种数据类型携带多少字节,然后使用 cmath 库中的 pow()。
这是我用于计算签名短头最大数量的数学/代码:(int)pow(2, sizeof(short)*8)-1;
这将输出最大无符号数,而不是最大有符号数。我可以将其除以 2,但不完全确定如何计算负部分,而不是在前面打印"-"。
我现在拥有的更详细的代码:
42 int shortmax_calculate;
43 shortmax_calculate = (pow(2, sizeof(short)*8)-1)/2;
44
45 float shortmin_calculate;
46 shortmin_calculate = (int)pow(2, sizeof(short)*8)/2;
47
48 short unsigned shortunsigned_calculate;
49 shortunsigned_calculate = pow(2, sizeof(short)*8)-1;
50
51 int intmax_calculate;
52 intmax_calculate = (int)pow(2, sizeof(int)*8)-1;
53
54
55 cout << "Maxmimum short (signed): "<< shortmax_calculate << endl;
56 cout << "Minimum short (signed): " << "-" << shortmin_calculate << endl;
57 cout << "Maximum short (unsigned): " << shortunsigned_calculate << endl;
58 cout << "Maximum int (signed): " << intmax_calculate << endl;
任何帮助不胜感激,谢谢。
假设您可以使用 C++11,请使用限制标准标头:
#include <iostream>
#include <limits>
...
{
std::cout << "Maxmimum short (signed): " <<
std::numeric_limits<short>::max() << std::endl;
// repeat replacing with 'unsigned short', 'int', 'unsigned int'
// in template class function: std::numeric_limits<type>, using
// max() or min() as required.
}
看看 clang 的实现 - 搜索__libcpp_numeric_limits
看看它是如何进行评估的。如果您不能使用 C++11,它可能会为您提供一些模板的想法。
在 2 的补码中,-1 将设置所有位。如果将其转换为无符号并将其右移 1,它将是可能的最大有符号数字,因为符号位将被替换为零。如果采用其按位逆数,它将是可能的最小负数。
short shortmax_calculate = static_cast<short>(static_cast<unsigned short>(-1) >> 1);
short shortmin_calculate = ~shortmax_calculate;
所以我认为你正在寻找的只是在你计算的最大值上添加一个。我在下面修改了你的代码(对不起,它在 C 中)。
short shortmax_calculate;
shortmax_calculate = (pow(2, sizeof(short)*8)-1)/2;
short shortmin_calculate;
shortmin_calculate = shortmax_calculate + 1;
short unsigned shortunsigned_calculate;
shortunsigned_calculate = pow(2, sizeof(short)*8)-1;
int intmax_calculate;
intmax_calculate = (int)pow(2, sizeof(int)*8)-1;
int intmin_calculate = intmax_calculate + 1;
printf("Maximum short (signed): %in",shortmax_calculate);
printf("Minimum short (signed): %in",shortmin_calculate);
printf("Maximum short (unsigned): %in", shortunsigned_calculate);
printf("Maximum int (signed): %in", intmax_calculate);
printf("Minimum int (signed): %in", intmin_calculate);
下面是代码的输出:
Maximum short (signed): 32767
Minimum short (signed): -32768
Maximum short (unsigned): 65535
Maximum int (signed): 2147483647
Minimum int (signed): -2147483648
这是因为计算机存储负数的方式。例如:最大短(带符号)是01111111即 127。最小签名存储为 10000000 (−128)。有关详细信息,请参阅此链接。
一些模板代码就可以完成这项工作。
#include <iostream>
#include <cstdint>
template <size_t S> struct Max
{
static intmax_t get()
{
return ((Max<S-1>::get() << 8) + 0xFF);
}
};
template <> struct Max<1>
{
static intmax_t get()
{
return 0x7F;
}
};
template <size_t S> struct Min
{
static intmax_t get()
{
return ((Min<S-1>::get() << 8));
}
};
template <> struct Min<1>
{
static intmax_t get()
{
return -0x80;
}
};
int main()
{
std::cout << "Max for int: " << Max<sizeof(int)>::get() << std::endl;
std::cout << "Min for int: " << Min<sizeof(int)>::get() << std::endl;
std::cout << "Max for short: " << Max<sizeof(short)>::get() << std::endl;
std::cout << "Min for short: " << Min<sizeof(short)>::get() << std::endl;
std::cout << "Max for signed char: " << Max<sizeof(signed char)>::get() << std::endl;
std::cout << "Min for signed char: " << Min<sizeof(signed char)>::get() << std::endl;
}
这是我在机器上得到的:
整数最大值:2147483647int 的最小值: -2147483648简称最大值:32767最小简称:-32768签名字符的最大数量:127签名字符的最小值:-128