C / C++中的nextafter()和nexttoward()

您将如何解决C / C++中的以下问题?

• C / C++中最小的可表示正浮点数是多少?
• C / C++中最大的可表示负浮点数是多少?
• 给定正浮点数x，找到小于x的最大可表示浮点值?

nextafter(x，y)和nexttoward(xy)
在C和C++中，nextafter(x，y)和nexttoward(xy)都是在math.h或cmath头文件中定义的相似函数。它们都在y方向上返回x之后的下一个可表示值。 nexttoward()具有更精确的第二个参数y。

以下程序演示了该概念：

// C program to demonstrate use of nextafter() and nexttoward()
#include 
#include 
int main ()
{
    // using nextafter
    printf ("Smallest positive floating point number : %e\n",
            nextafter(0.0, 1.0));
    printf ("Largest negative floating point number :%e\n",
            nextafter(0.0, -1.0));
    printf ("Largest positive floating point number smaller than 0.5 : %e\n",
            nextafter(0.5, 0.0));
  
    // using nexttoward
    printf ("Smallest positive floating point number : %e\n",
            nexttoward(0.0, 1.0));
    printf ("Largest negative floating point number : %e\n",
            nexttoward(0.0, -1.0));
    printf ("Largest positive floating point number smaller than 0.5 : %e\n",
            nexttoward(0.5, 0.0));
    return (0);
}

输出：

nextafter first value greater than zero: 4.940656e-324
nextafter first value less than zero: -4.940656e-324
nexttoward first value greater than zero: 4.940656e-324
nexttoward first valnextafter first value greater than zero: 4.940656e-324
nextafter first value less than zero: -4.940656e-324
nexttoward first value greater than zero: 4.940656e-324
nexttoward first value less than zero: -4.940656e-324 ue less than zero: -4.940656e-324 

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