Static local variable in Go - go

Question

Is it possible to define a local variable in Go that can maintain its value from one function call to another? In C, we can do this using the reserved word static.
Example in C:
int func() {
static int x = 0;
x++;
return x;
}

Answer 1

Use a closure:
Function literals are closures: they may refer to variables defined in
a surrounding function. Those variables are then shared between the
surrounding function and the function literal, and they survive as
long as they are accessible.
It doesn't have to be in global scope, just outside the function definition.
func main() {
x := 1
y := func() {
fmt.Println("x:", x)
x++
}
for i := 0; i < 10; i++ {
y()
}
}
(Sample on the Go Playground)

Answer 2

You can do something like this
package main
import (
"fmt"
)
func main() {
f := do()
f() // 1
f() // 2
}
func do() (f func()){
var i int
f = func(){
i++
fmt.Println(i)
}
return
}
Link on Playground https://play.golang.org/p/D9mv9_qKmN

Answer 3

Declare a var at global scope:
var i = 1
func a() {
println(i)
i++
}

Answer 4

Like Taric' suggestion, but with staticCounter() returning an int function
package main
import (
"fmt"
)
func staticCounter() (f func()(int)){
var i int
f = func()(int){
i++
// fmt.Println(i)
return i
}
return
}
func main() {
f := staticCounter()
g := staticCounter()
fmt.Println(f())
fmt.Println(f())
fmt.Println(f())
fmt.Println(f())
fmt.Println(g())
fmt.Println(g())
}

Answer 5

Use Function closure
In following example, variable sum behaves like a separate static for each closure a1 and a2.
package main
import "fmt"
func adder() func(int) int {
sum := 0
return func(x int) int {
sum += x
return sum
}
}
func main() {
a1,a2 := adder(), adder()
for i := 0; i < 10; i++ {
fmt.Println(
a1(i),
a2(-1*i),
)
}
}
Output
0 0
1 -1
3 -3
6 -6
10 -10
15 -15
21 -21
28 -28
36 -36
45 -45

Answer 6

In all the other answers, the function containing a static variable is assigned in the main.
Here is how you can define and assign that function in the global scope.
var myFunction = func() func(type1, type2) type3 {
myStaticVariable := []string {"hello", "world"}
return func(arg1 type1, arg2 type2) type3 {
// use arg1, arg2 and myStaticVariable here
}
}()

Answer 7

// A var x1 is local to main(), is not a global var.
// A static var is one that can't be accesed from others functions just
// like global vars.
// A static var dont disappears when the function ends.
// So is what x1 n x2 are pretending in this program.
package main
import (
"fmt"
)
/*
int func() { // x static inside a function.
static int x = 0;
x++;
return x;
}
*/
//
func main() {
//
var x1 int = 0
var x2 int = 100
//
for i := 0; i < 10; i++ { // call to a "static" var x
x1 = fun1(&x1)
x2 = fun2(&x2)
fmt.Printf("%d %d \n", x1, x2)
} //
test1(x1, x2) // a funct needs parameters to see x1 n x2
} //main
//
func fun1(p *int) int {
//
*p++ // save value
return *p //counter x1
}
//
func fun2(p *int) int {
*p++ // save value
return *p //counter x2
}
//
func test1(x1 int, x2 int) {
fmt.Println("\"x1\" y \"x2\" ", x1, x2)
}