Go Function

Apr 20, 2023

# Function Closure

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	f2, f1 := 0, 1
	// return a function
	return func() int {
		f := f2
		f2, f1 = f1, f+f1
		return f
	}
}

func main() {
	f := fibonacci() // assign
	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

# Methods

A method is just a function with a receiver argument.

func (v Vertex) Abs() float64 {
	return math.Sqrt(v.X*v.X + v.Y*v.Y)
}
// (v Vertex) is a receiver

You can only declare a method with a receiver whose type is defined in the same package as the method. You cannot declare a method with a receiver whose type is defined in another package (which includes the built-in types such as int).

You can declare methods with pointer receivers.

func (v *Vertex) Scale(f float64) {
	v.X = v.X * f
	v.Y = v.Y * f
}

Go interprets the statement v.Scale(5) as (&v).Scale(5) since the Scale method has a pointer receiver.