Created
April 2, 2012 01:58
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An answer of the exercise: Loops and Functions on a tour of Go
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package main | |
import ( | |
"fmt" | |
"math" | |
) | |
const Delta = 0.0001 | |
func isConverged(d float64) bool { | |
if d < 0.0 { | |
d = -d | |
} | |
if d < Delta { | |
return true | |
} | |
return false | |
} | |
func Sqrt(x float64) float64 { | |
z := 1.0 | |
tmp := 0.0 | |
for { | |
tmp = z - (z * z - x) / 2 * z | |
if d := tmp - z; isConverged(d) { | |
return tmp | |
} | |
z = tmp | |
} | |
return z | |
} | |
func main() { | |
attempt := Sqrt(2) | |
expected := math.Sqrt(2) | |
fmt.Printf("attempt = %g (expected = %g) error = %g\n", | |
attempt, expected, attempt - expected) | |
} |
Can anyone let me know the different of z -= (z*z - x) / (2 * x)
and z -= (z * z - x)/(2 * z)
in attached example?
The result is different between these expressions which make me very confuse
You can find the full code here https://go.dev/play/p/ff8LzDMIg8c
package main
import (
"fmt"
"math"
)
func Sqrt(x float64) float64 {
z,p := 1.0, 0.0
for math.Abs(p-z) >= 1e-8 {
p,z = z, z - (z*z - x) / (2*z)
}
return z
}
func main() {
fmt.Println(Sqrt(2))
}
package main
import (
"fmt"
"math"
)
func Sqrt(x float64) (z float64, iterations int) {
z = 1.0
iterations = 0
for {
iterations++
temp := z - (z*z - x) / (2*z)
if math.Round(temp * 100000) / 100000 == math.Round(z * 100000) / 100000 {
break
}
z = temp
}
return
}
func main() {
fmt.Println(Sqrt(2))
fmt.Println(math.Sqrt(2))
}
As a total beginner I've done it with rounding
package main
import (
"fmt"
)
func Sqrt(x float64) float64 {
z := 1.0
for i := 0; i <= 10; i++ {
z -= (z*z - x) / (2 * z)
}
return z
}
func main() {
fmt.Println(Sqrt(23123))
}
package main
import (
"fmt"
"math"
)
func Sqrt(x float64) float64 {
z:=1.0
for n:= 1;n < 10;n++ {
z = z - ((z*z - x) / (2*z))
}
return z
}
func main() {
y := 169.
fmt.Println(Sqrt(y))
fmt.Println(math.Sqrt(y))
}
func Sqrt(x float64) float64 {
var z, tmp float64 = 1.0, 0.
for ; math.Abs(z - tmp) >= 1e-8 ; z, tmp = z - (zz-x)/(2z), z {}
return z
}
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package main
import (
"fmt"
"math"
)
func Sqrt(x float64) float64 {
z,t := 1.,0.
}
func main() {
guess := Sqrt(2)
expected := math.Sqrt(2)
fmt.Printf("Guess: %v, Expected: %v, Error: %v", guess, expected, math.Abs(guess - expected))
}