initial commit

interfaces/interfaces.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+// here is a basic interface for geometric shapes
+type geometry interface {
+	area() float64
+	perim() float64
+}
+
+//for our example well implement this interface on rect and circle types
+type rect struct {
+	width,height float64
+}
+type circle struct {
+	radius float64
+}
+
+// to implement an interface in Go,
+//we just need to implement all the methods in the interface
+//here we do it for rectangles
+func (r rect) area() float64 {
+	return r.width * r.height
+}
+func (r rect) perim() float64 {
+	return 2*r.width + 2*r.height
+}
+//here we do it for circles
+func (c circle) area() float64 {
+	return math.Pi * c.radius * c.radius
+}
+func (c circle) perim() float64 {
+	return 2*math.Pi*c.radius
+}
+
+//if a variable has an interface type,
+// then we can call methods that are in the named interface
+//here's a generic measure function taking advantage of this 
+//to work on any geometry
+func measure(g geometry) {
+	fmt.Println(g)
+	fmt.Println(g.area())
+	fmt.Println(g.perim())
+}
+
+func main(){
+	r := rect{width: 3,height: 4}
+	c := circle{radius:5}
+
+	measure(r)
+	measure(c)
+}