C++ 测试案例

infinity()

#include <iostream>
#include <limits>int main() {double inf = std::numeric_limits<double>::infinity();std::cout << "Infinity (double): " << inf << std::endl;// 可以用来与其他值进行比较if (inf > 1000000) {std::cout << "Infinity is greater than 1 million!" << std::endl;}return 0;
}

# g++ testInf.cpp -o testInf
# ./testInf 
Infinity (double): inf
Infinity is greater than 1 million!

nextafter

# cat nextafter.cpp
#include <iostream>
#include <cmath>
#include <limits>
#include <iomanip>template <typename TNum>
TNum roundToDecimals(TNum number, int decimals) {// 计算放大倍数long double factor = std::pow(10.0L, static_cast<long double>(decimals));// 定义正无穷static const TNum kInf = std::numeric_limits<TNum>::infinity();// 如果 number 是负数if (number < 0) {return static_cast<TNum>(std::round(std::nextafter(number, -kInf) * factor) / factor);}// 如果 number 是正数return static_cast<TNum>(std::round(std::nextafter(number, kInf) * factor) / factor);
}int main() {// 测试数据double number1 = 194.71512499999997;int decimals1 = 5;double number2 = -194.71512499999997;int decimals2 = 5;// 调用四舍五入函数并输出结果std::cout << std::setprecision(8) << "Rounded value of " << number1 << " to " << decimals1 << " decimals: "<< roundToDecimals(number1, decimals1) << std::endl;std::cout << std::setprecision(8) << "Rounded value of " << number2 << " to " << decimals2 << " decimals: "<< roundToDecimals(number2, decimals2) << std::endl;return 0;
}

# ./nextafter
Rounded value of 194.71512 to 5 decimals: 194.71513
Rounded value of -194.71512 to 5 decimals: -194.71513

测试 nextafter

        long double factor = std::pow(10.0L, static_cast<long double>(decimals1));static const double kInf = std::numeric_limits<double>::infinity();std::cout << std::setprecision(15) << "std::nextafter(number, kInf)" << std::nextafter(number1, kInf) << std::endl;

# ./nextafterdebug
std::nextafter(number, kInf)194.715125
Rounded value of 194.71512 to 5 decimals: 194.71513

std::round()

round() 函数是 C++ 中的一个用于四舍五入的函数。它可以接受一个浮点数作为输入，并返回一个最接近输入值的整数。