What's wrong with this code?
package main import "fmt" // fibonacci is a function that returns // a function that returns an int. func fibonacci() func() int { prev := 0 curr := 1 return func() int { temp := curr curr := curr + prev prev := temp return curr } } func main() { f := fibonacci() for i := 0; i < 10; i++ { fmt.Println(f()) } } prog.go:13: prev declared and not used
You declared a variable named prev and then never used it.
Specifically, you said prev := temp. This is creating a new local variable in the current scope named prev. I assume you meant to just say prev = temp, which modifies the prev variable inherited from the surrounding scope. Similarly you probably meant to say curr = curr + prev on the previous line, instead of using :=.
If you make the changes suggested by Kevin Ballard, then,
package main import "fmt" // fibonacci is a function that returns // a function that returns an int. func fibonacci() func() int { prev := 0 curr := 1 return func() int { temp := curr curr = curr + prev prev = temp return curr } } func main() { f := fibonacci() for i := 0; i < 10; i++ { fmt.Println(f()) } } Output:
1 2 3 5 8 13 21 34 55 89 The output is not the Fibonacci sequence.
For the Fibonacci sequence,
package main import "fmt" func fibonacci() func() int { a, b := 0, 1 return func() (f int) { f, a, b = a, b, a+b return } } func main() { f := fibonacci() for i := 0; i < 10; i++ { fmt.Println(f()) } } Output:
0 1 1 2 3 5 8 13 21 34 
curr = curr + prev with just curr += prev. There's no functional difference, of course - just slightly fewer keystrokes.
