commit more tour exercises

indirection-values.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v Vertex) Abs() float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func AbsFunc(v Vertex) float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func main() {
+    v := Vertex{3, 4}
+    fmt.Println(v.Abs())
+    fmt.Println(AbsFunc(v))
+
+    p := &Vertex{4, 3}
+    fmt.Println(p.Abs())
+    fmt.Println(AbsFunc(*p))
+}

indirection.go

@@ -0,0 +1,29 @@
+package main
+
+import "fmt"
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v *Vertex) Scale(f float64) {
+    v.X = v.X * f
+    v.Y = v.Y * f
+}
+
+func ScaleFunc(v *Vertex, f float64) {
+    v.X = v.X * f
+    v.Y = v.Y * f
+}
+
+func main() {
+    v := Vertex{3, 4}
+    v.Scale(2)
+    ScaleFunc(&v, 10)
+
+    p := &Vertex{4, 3}
+    p.Scale(3)
+    ScaleFunc(p, 8)
+
+    fmt.Println(v, p)
+}

interfaces.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Abser interface {
+    Abs() float64
+}
+
+func main() {
+    var a Abser
+    f := MyFloat(-math.Sqrt2)
+    v := Vertex{3, 4}
+
+    a = f  // a MyFloat implements Abser
+    a = &v // a *Vertex impelments Abser
+
+    // In the following line, v is a Vertex (not *Vertex)
+    // and does NOT implement Abser.
+    // a = v
+
+    fmt.Println(a.Abs())
+}
+
+type MyFloat float64
+
+func (f MyFloat) Abs() float64 {
+    if f < 0 {
+        return float64(-f)
+    }
+    return float64(f)
+}
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v *Vertex) Abs() float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}

methods-continued.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type MyFloat float64
+
+func (f MyFloat) Abs() float64 {
+    if f < 0 {
+        return float64(-f)
+    }
+    return float64(f)
+}
+
+func main() {
+    f := MyFloat(-math.Sqrt2)
+    fmt.Println(f.Abs())
+}

methods-funcs.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func Abs(v Vertex) float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func main() {
+    v := Vertex{3 ,4}
+    fmt.Println(Abs(v))
+}

methods-pointers-explained.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func Abs(v Vertex) float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func Scale(v *Vertex, f float64) {
+    v.X = v.X * f
+    v.Y = v.Y * f
+}
+
+func main() {
+    v := Vertex{3, 4}
+    Scale(&v, 10)
+    fmt.Println(Abs(v))
+}

methods-pointers.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v Vertex) Abs() float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func (v *Vertex) Scale(f float64) {
+    v.X = v.X * f
+    v.Y = v.Y * f
+}
+
+func main() {
+    v := Vertex{3, 4}
+    v.Scale(10)
+    fmt.Println(v.Abs())
+}

methods-with-pointer-receivers.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v *Vertex) Scale(f float64) {
+    v.X = v.X * f
+    v.Y = v.Y * f
+}
+
+func (v *Vertex) Abs() float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func main() {
+    v := &Vertex{3, 4}
+    fmt.Printf("Before scaling: %+v, Abs: %v\n", v, v.Abs())
+    v.Scale(5)
+    fmt.Printf("After scaling: %+v, Abs: %v\n", v, v.Abs())
+}

methods.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type Vertex struct {
+    X, Y float64
+}
+
+func (v Vertex) Abs() float64 {
+    return math.Sqrt(v.X * v.X + v.Y * v.Y)
+}
+
+func main() {
+    v := Vertex{3 ,4}
+    fmt.Println(v.Abs())
+}