使用C/C++ nextafter / nexttoward函数无法获得下一个32位浮点值

就像是：
for(float f = FLOAT_MIN; f< MAX; f = Next_Float(f))
{…}

我认为我可以使用标准数学库中的“nexttoward”或“nextafter”函数来完成该任务.见http://www.cplusplus.com/reference/cmath/nextafter/

现在,当我测试带有双打或长双打的“nexttoward”或“nextafter”函数并在Ubuntu 13.04上使用g 4.7进行编译时,我没有遇到任何问题.查看测试代码：

#include <math.h>   
#include <iostream>
#include <iomanip>

int main ()
{
    double f = 0.1;
    for(int i = 0; i < 5; ++i)
    {
    //Marginally increment f in the upper direction.
    f = nexttoward(f,999.999);
    std::cout << std::setprecision(70) << f << std::endl;
    std::cout << nexttoward(f,999.999) << std::endl;
    }
  return 0;
}

该程序的浮点输出值按预期稳步增长：

ubuntu @ ubuntu：?$g -o temp~ / temp.cpp

ubuntu @ ubuntu：?$./temp

0.10000000000000001942890293094023945741355419158935546875
0.100000000000000033306690738754696212708950042724609375
0.100000000000000033306690738754696212708950042724609375
0.10000000000000004718447854656915296800434589385986328125
0.10000000000000004718447854656915296800434589385986328125
0.1000000000000000610622663543836097232997417449951171875
0.1000000000000000610622663543836097232997417449951171875
0.10000000000000007494005416219806647859513759613037109375
0.10000000000000007494005416219806647859513759613037109375
0.100000000000000088817841970012523233890533447265625

Ubuntu的@ Ubuntu的：?$

但是当我尝试使用浮点数而不是双精度数时,“nexttoward”和“nextafter”函数使我失败 – 函数似乎返回比32位浮点数更高精度的值,并且当我将返回值赋给我的32位浮点数时,浮动保持其原始值而不是上升到下一个更高的值.请参阅示例代码和输出：

#include <math.h>    
#include <iostream>
#include <iomanip>

int main ()
{
    float f = 0.1f;
    for(int i = 0; i < 10; ++i)
    {
    //Marginally increment f in the upper direction.
    f = nexttoward(f,999.999f);
    std::cout << std::setprecision(70) << f << std::endl;
    std::cout << nexttoward(f,999.999f) << std::endl;
    }
  return 0;
}

请注意,“nexttoward”的第二个输出值具有更高的精度,并且f保持相同的值：

ubuntu @ ubuntu：?$g -o temp~ / temp.cpp

ubuntu @ ubuntu：?$./temp

0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625
0.100000001490116119384765625
0.10000000149011613326255343281445675529539585113525390625

我想增加所有32位浮点值,而不是所有64位双精度值 – 增加所有双精度值的时间太长.

如何解决此问题并实现高效,方便,可移植的方式迭代32位浮点变量的范围？