浮点数格式化输出的原理是什么？

 

fmt.Printf("1.8350 =>  %.2f\n",float64(1.835))
fmt.Printf("1.8450 =>  %.2f\n",float64(1.845))

fmt.Printf("5.8350 =>  %.2f\n",float64(5.835))
fmt.Printf("5.8450 =>  %.2f\n",float64(5.845))

fmt.Printf("7.8350 =>  %.2f\n",float64(7.835))
fmt.Printf("7.8450 =>  %.2f\n",float64(7.845))

fmt.Printf("8.8350 =>  %.2f\n",float64(8.835))
fmt.Printf("8.8450 =>  %.2f\n",float64(8.845))

fmt.Printf("9.8350 =>  %.2f\n",float64(9.835))
fmt.Printf("9.8450 =>  %.2f\n",float64(9.845))

输出结果：

1.8350 =>  1.83
1.8450 =>  1.84
5.8350 =>  5.83
5.8450 =>  5.84
7.8350 =>  7.83
7.8450 =>  7.84
8.8350 =>  8.84
8.8450 =>  8.85
9.8350 =>  9.84
9.8450 =>  9.85

为什么有时进位有时没有

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