Go Tour Exercises

errors.go

package main

import (
    "fmt"
    "math"
)

type ErrNegativeSqrt float64

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

func Sqrt(x float64) (float64, error) {    
    if x < 0 {
        return 0, ErrNegativeSqrt(x)
    }
    
    z, result := 2.0, 0.0
    
    for {
        z = z - (z * z - x) / (2 * z)
        if math.Abs(result-z) < 1e-15 {
            break
        }
        result = z
    }
    return result, nil
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(Sqrt(-2))
}

loops_and_functions.go

package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {    
  z, result := 2.0, 0.0
    
    for {
        z = z - (z * z - x) / (2 * z)
        if math.Abs(result-z) < 1e-15 {
            break
        }
        result = z
    }
    return result
}

func main() {
    fmt.Println(Sqrt(2))
    fmt.Println(math.Sqrt(2))
}

maps.go

package main

import (
  "code.google.com/p/go-tour/wc"
	"fmt"
	"strings"
)

func WordCount(s string) map[string]int {
	fields := strings.Fields(s)
	ret := make(map[string]int, len(fields))

	for _, s := range fields {
		fmt.Println(s)
		ret[s] += 1
	}

	return ret
}

func main() {
	wc.Test(WordCount)
}