My implementation of the Errors Exercise in Go, printing errors if a negative number is run through the Sqrt function. Part of the Go tour: http://tour.golang.org/#55

SqrtErrors.go

package main

import (
    "fmt"
    "math"
)

const(
  ACCURACY_DELTA = 0.00000000000001 // Experiment with this value to see accuracy impact!
)

type ErrNegativeSqrt float64 

func (e ErrNegativeSqrt) Error() string{
    return fmt.Sprintf("Cannot Sqrt negative number: %g", float64(e))
    
}

func Sqrt(x float64) (float64, error){
    
    if x < 0 {
    	return 0, ErrNegativeSqrt(x)
	}
    
    ourGuess := float64(1) // any initial guess will do!
    
    for newtonGuess := newtonIteration(x, ourGuess); math.Abs(newtonGuess-ourGuess) > ACCURACY_DELTA
    {
    	ourGuess = newtonGuess;
        newtonGuess = newtonIteration(x, ourGuess)
    }
        
    return ourGuess, nil
}

func newtonIteration(x, z float64) float64{
    return z-(math.Pow(z,2)-x)/(2*z)
}

func main() {

    // Is there really not a better syntax for this error handling?
    res, err := Sqrt(2)
    if err != nil {
    	fmt.Println(err)    
    }else{
        fmt.Println(res)
    }	
    
    res, err = Sqrt(-2)
    if err != nil {
    	fmt.Println(err)    
    }else{
        fmt.Println(res)
    }
}