How Can I Resolve the \'Declared but Not Used\' Error in Go?

"Declared and Not Used" Error in Go

When encountering the "declared and not used" error, it's important to scrutinize the variable usage within the code. This issue often arises when the variable's declaration and usage differ due to scoping rules or assignment syntax.

Consider the following code snippet:

func Sqrt(x float64) float64 {

    z := float64(x)

    for i := 0; i < 10; i++ {
        z = z - (z*z - x) / (2 * z);
    }

    return z;
}

The error arises because the for-loop declares a new variable named z using the := syntax. This shadows the outer z variable, giving the impression that the variable is used. To resolve this issue, replace := with = in the for-loop:

func Sqrt(x float64) float64 {

    z := x

    for i := 0; i < 10; i++ {
        z = z - (z*z - x) / (2 * z);
    }

    return z;
}

It's also worth noting that the provided implementation can be optimized for precision and speed:

func Sqrt(x float64) float64 {
    z := x
    for i := 0; i < 5; i++ {
        a := z + x/z
        z = a/4 + x/a
    }
    return z
}

This implementation combines two iterations of the original into a single step, resulting in an improvement in efficiency and accuracy.

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