I've searched older questions, there are tons of them. However I couldn't find the answer to my case.
func fibonacci() func() int {
y := 0
z := 1
return func () int {
res := y + z
y = z
z = res
return res
}
}
func main() {
f := fibonacci()
for i := 0; i < 10; i++ {
fmt.Println(f())
}
}
This produces 1 2 3 5 8
What should I change (as little as possible) to get 0 1 1 2 3 5 8 ?
Actually I managed to solve that if initial y and z were like this:
y := -1
z := 1
But that's a fortunate hack, and I want a logical solution.
Change your function to return res to this:
return func () int {
res := y
y = z
z = res + z
return res
}
This way you output the initial values first, and calculate the next values. Your current solution overwrites the initial values before they are returned.
For example,
package main
import "fmt"
// fibonacci returns a function that returns
// successive Fibonacci numbers.
func fibonacci() func() int {
a, b := 0, 1
return func() (f int) {
if a < 0 {
panic("overflow")
}
f, a, b = a, b, a+b
return f
}
}
func main() {
f := fibonacci()
for i := 0; i < 10; i++ {
fmt.Println(f())
}
}
Playground: https://play.golang.org/p/uYHEK_ZgE6K
Output:
0
1
1
2
3
5
8
13
21
34
If you added:
x := y
and changed the return statement to
return x
you would be returning the initial y := 0 value, instead of the computed res := y + z, so returning the values 2 earlier in the sequence, giving you 0, 1, 1, 2, 3, 5, ...
(But I wouldn’t consider the -1, 1 initializer a hack.)