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Go

// Go supports [_anonymous functions_](http://en.wikipedia.org/wiki/Anonymous_function),
// which can form <a href="http://en.wikipedia.org/wiki/Closure_(computer_science)"><em>closures</em></a>.
// Anonymous functions are useful when you want to define
// a function inline without having to name it.
package main
import "fmt"
// This function `intSeq` returns another function, which
// we define anonymously in the body of `intSeq`. The
// returned function _closes over_ the variable `i` to
// form a closure.
func intSeq() func() int {
i := 0
return func() int {
i++
return i
}
}
func main() {
// We call `intSeq`, assigning the result (a function)
// to `nextInt`. This function value captures its
// own `i` value, which will be updated each time
// we call `nextInt`.
nextInt := intSeq()
// See the effect of the closure by calling `nextInt`
// a few times.
fmt.Println(nextInt())
fmt.Println(nextInt())
fmt.Println(nextInt())
// To confirm that the state is unique to that
// particular function, create and test a new one.
newInts := intSeq()
fmt.Println(newInts())
}