Go Function

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.

Variadic Parameter

slice1 := []int{0, 1, 2, 3, 4}
slice2 := []int{55, 66, 77}
fmt.Println(slice1)
slice1 = Append(slice1, slice2...) // The '...' is essential!
fmt.Println(slice1)

1. Defining Variadic Functions: When defining a function, the ... operator allows you to specify that the function can take any number of arguments of a specified type. This is similar to variadic functions in other programming languages like C’s printf or Python’s *args.
2. Passing Arguments to Variadic Functions: When calling a variadic function, you can use the ... operator to pass a slice as multiple arguments. The Append function is a variadic function that can take multiple integers as arguments. By writing slice2..., you are essentially spreading out the elements of slice2 as individual arguments to the Append function.