float浮点数相比较会导致的错误!(浮点数精度导致的坑！！！)_float t = 0.f

以前从来没有在意浮点数精度会导致错误，但现在自己遇到了～～

如果有两个浮点数a , b，用a == b去作为某个判断条件，那么大概率会出现bug，并且如果也像我一样，对精度问题不在意，可能摸不着头脑！

所以，建议用fabs(a-b) < 1e-6的方式，去判断两个浮点数是否相等，而这个1e-6就是项目要求的精度啦，可以随情况修改

以下做两组实验验证这一结论

1.两个浮点数直接比较

        float t = 0.0f,T = 0.005f;
		
	   //让t随着i增长而累加T，然后判断t与i*T是否相等
	   
        for(auto i = 0;i < 20;i++){
            std::cout << "t:" << t << "   i*T:" << i*T << "   is equal:" <<  (t == i*T)  <<std::endl;
            t += T;
        }
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运行结果

// is equal 中，1代表系统判断相等,0代表系统判断不相等
t:0   i*T:0   is equal:1
t:0.005   i*T:0.005   is equal:1
t:0.01   i*T:0.01   is equal:1
t:0.015   i*T:0.015   is equal:1
t:0.02   i*T:0.02   is equal:1
t:0.025   i*T:0.025   is equal:1
t:0.03   i*T:0.03   is equal:0
t:0.035   i*T:0.035   is equal:0
t:0.04   i*T:0.04   is equal:0
t:0.045   i*T:0.045   is equal:0
t:0.05   i*T:0.05   is equal:0
t:0.055   i*T:0.055   is equal:0
t:0.06   i*T:0.06   is equal:0
t:0.065   i*T:0.065   is equal:0
t:0.07   i*T:0.07   is equal:0
t:0.075   i*T:0.075   is equal:1
t:0.08   i*T:0.08   is equal:1
t:0.085   i*T:0.085   is equal:1
t:0.09   i*T:0.09   is equal:0
t:0.095   i*T:0.095   is equal:0
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由此可见，直接让系统判断两个浮点数是否相等的方式非常不靠谱～～

2.利用fabs()比较

        float t = 0.0f,T = 0.005f;
		
	   //让t随着i增长而累加T，然后判断t与i*T是否相等
        for(auto i = 0;i < 20;i++){
            std::cout << "t:" << t << "   i*T:" << i*T << "   is equal:" << (fabs(t -i*T) < 1e-6)  <<std::endl;
            t += T;
        }
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运行结果

// is equal 中，1代表系统判断相等,0代表系统判断不相等
t:0   i*T:0   is equal:1
t:0.005   i*T:0.005   is equal:1
t:0.01   i*T:0.01   is equal:1
t:0.015   i*T:0.015   is equal:1
t:0.02   i*T:0.02   is equal:1
t:0.025   i*T:0.025   is equal:1
t:0.03   i*T:0.03   is equal:1
t:0.035   i*T:0.035   is equal:1
t:0.04   i*T:0.04   is equal:1
t:0.045   i*T:0.045   is equal:1
t:0.05   i*T:0.05   is equal:1
t:0.055   i*T:0.055   is equal:1
t:0.06   i*T:0.06   is equal:1
t:0.065   i*T:0.065   is equal:1
t:0.07   i*T:0.07   is equal:1
t:0.075   i*T:0.075   is equal:1
t:0.08   i*T:0.08   is equal:1
t:0.085   i*T:0.085   is equal:1
t:0.09   i*T:0.09   is equal:1
t:0.095   i*T:0.095   is equal:1
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利用这种方式去判断，就可以得到令人放心的结果！