寻找每种数值数据类型的限制时遇到问题

Question

我正在使用 Bjarne Stroustrup 的《C++ 编程语言》学习 C++，同时做练习 4.5（在您的系统上，以下类型的最大和最小值是什么：char、short、int、long、float、double ，长双精度，无符号）我写道：

#include <iostream>
#include <limits>

using namespace std;
int main(){
    cout << "\nExercise 4.11.5:\n";

    cout << "Largest and smallest values for different data types:\n";

    // char ???!??!?!?!?!?
    cout << "char: " << static_cast<int>(numeric_limits<char>::min()) << " to "
         << static_cast<int>(numeric_limits<char>::max()) << endl;

    // unsigned char
    cout << "unsigned char: " << static_cast<int>(numeric_limits<unsigned char>::min()) << " to "
         << static_cast<int>(numeric_limits<unsigned char>::max()) << endl;

    // short
    cout << "short: " << numeric_limits<short>::min() << " to "
         << numeric_limits<short>::max() << endl;

    // int
    cout << "int: " << numeric_limits<int>::min() << " to "
         << numeric_limits<int>::max() << endl;

    // float
    cout << "float: " << numeric_limits<float>::lowest() << " to "
         << numeric_limits<float>::max() << endl;

    // double
    cout << "double: " << numeric_limits<double>::lowest() << " to "
         << numeric_limits<double>::max() << endl;

    // long double
    cout << "long double: " << numeric_limits<long double>::lowest() << " to "
         << numeric_limits<long double>::max() << endl;

    // unsigned
    cout << "unsigned: " << 0 << " to "
         << numeric_limits<unsigned>::max() << endl;
    }

输出是真的很奇怪：

Exercise 4.11.5:
Largest and smallest values for different data types:
char: 37777777600 to 177
unsigned char: 0 to 377
short: 100000 to 77777
int: 20000000000 to 17777777777
float: -3.40282e+38 to 3.40282e+38
double: -1.79769e+308 to 1.79769e+308
long double: -1.79769e+308 to 1.79769e+308
unsigned: 0 to 37777777777

有人知道为什么这些值是错误的吗？ 我期望 char 为 -128 到 127。

Answer 1

按照向导（@Iłya Bursov，和@n.m.可能是人工智能）的建议，问题是我在十月显示答案（由于同一文件中的另一个练习，没有在问题中提出，但他们解决了） ).

int main(){
// (...)
// Exercise 4.11.4:
    cout << "\nExercise 4.11.4:\n";
    for (int i = 48; i < 127; i++)
    {
        cout
            << char(i) << " Hex:" << hex << i << " Dec:" << dec << i << " Oct:" << oct << i << "" << endl;
    }
    cout << dec << endl; // FIXING TO DEC.
    cout << "\nExercise 4.11.5:\n";

    cout << "Largest and smallest values for different data types:\n";

    // char ???!??!?!?!?!?
    cout << "char: " << static_cast<int>(numeric_limits<char>::min()) << " to "
         << static_cast<int>(numeric_limits<char>::max()) << endl;

    // unsigned char
    cout << "unsigned char: " << static_cast<int>(numeric_limits<unsigned char>::min()) << " to "
         << static_cast<int>(numeric_limits<unsigned char>::max()) << endl;

    // short
    cout << "short: " << numeric_limits<short>::min() << " to "
         << numeric_limits<short>::max() << endl;

    // int
    cout << "int: " << numeric_limits<int>::min() << " to "
         << numeric_limits<int>::max() << endl;

    // float
    cout << "float: " << numeric_limits<float>::lowest() << " to "
         << numeric_limits<float>::max() << endl;

    // double
    cout << "double: " << numeric_limits<double>::lowest() << " to "
         << numeric_limits<double>::max() << endl;

    // long double
    cout << "long double: " << numeric_limits<long double>::lowest() << " to "
         << numeric_limits<long double>::max() << endl;

    // unsigned
    cout << "unsigned: " << 0 << " to "
         << numeric_limits<unsigned>::max() << endl;
}