A Tour of Go Exercise: Fibonacci closure

44.go

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 func() int {
		f := f2
		f2, f1 = f1, f+f1

		return f
	}
}

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

Here is my solution -

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	x, y := 0, 1
	return func() int{
		x++
		y++
		return (x-1)+(y-2)
	}

}

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

Not as elegant but doing the job:

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	i := -1
	f1 := 0
	f2 := 1
	return func() int {
		switch i+=1; i {
		case 0:
			return 0	
		case 1:
			return 1
		default:
			f := f1 + f2
			f1 = f2
			f2 = f
			return f
		}
	}
}

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

We can omit the variable f with

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.

func fibonacci() func() int {
	f1, f2 := 0, 1
	return func() int {
		f1, f2 = f2, f1+f2
		return f1
	}
}

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

similar to other solutions using if statements
Hope it helps someone out there

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func(int) int {
	
	prev2 := 0
	prev1 := 1
	
	return func(x int ) int{
		
		sum:=0
		
		//SKIPPING FIRST 2 ITTERATION
		if x == 0{
			return 0
		}else if x == 1{
			return 1
		}else{
			//Staring at 2 value should still be 1
			sum = prev1 + prev2
		}
	
		//THEN MAKE PREVIOUS VALUES CURRENT FOR NEXT ITTERATION
		prev2 = prev1 
		prev1 = sum 
		
		
		//RETURN THE RESULT
		return fib
	}
	
}

func main() {
	//Assigning a function fibonacci
	f := fibonacci()
	
	//now looping through and passing i each time
	for i := 0; i < 10; i++ {
		fmt.Println(i,"->",f(i))
	}
}

package main

import "fmt"

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

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

With defer

func fibonacci() func() int {
	var v0, v1 int = 0,1
	advance := func () {
		v0, v1 = v1, v0+v1
	}
	return func() int {
		defer advance()
		return v0
	}
}

package main

import "fmt"

func fibonacci() func() uint64 {
	
	a := uint64(0)
	b := uint64(0)
	c := uint64(a + b)

	return func() uint64 {
		if c-a > c-b {
			c = c + (c - a)
			a = c - b
			return c
		} else if c-a < c-b {
			c = c + (c - b)
			b = c - a
			return c
		} else if c == c {
			a += 0
			b += 1
			c += 1
			return c
		}
		return c
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 1000; i++ {
		fmt.Println(f())
	}
}

package main

import "fmt"

func fibonacci() func() int {
	f := [10]int{0, 1}
	i := 0

	return func() int {
		last := i
		i++

		if last == 0 || last == 1 {
			return f[last]
		}

		f[last] = f[last-1] + f[last-2]

		return f[last]
	}
}

func main() {
	f := fibonacci()

	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

package main

import "fmt"

func fibonacci() func() int {
	fib, temp, next := 0, 0, 1
	
	return func() int {
		fib = temp
		temp = next
		next = fib + temp
		return fib
	}
}

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

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	num := 0
	nextNum := 1
	advance := func () {
		temp := nextNum
		nextNum = num + nextNum
		num = temp
	}
	return func () int {
		defer advance()
		return num
	}
}

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

package main

import "fmt"

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

func main() {
f := fibonacci()
for i := 0; i < 100; i++ {
fmt.Println(f())
}
}

package main

import "fmt"

func fibonacci() func() int {
	a, b := 1, 0
	return func() int {
		a, b = b, a + b
		return a
	}
}

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