fn main() {
	a1 := [1,2,3,4].filter(fn(a int, b int) bool { return a > 0 })
	println(a1)

	a2 := [1,2,3,4].filter(fn(a string) bool { return a.len > 0 })
	println(a2)

	a3 := [1,2,3,4].filter(fil1)
	println(a3)

	a4 := [1,2,3,4].filter(fil2)
	println(a4)
}

fn fil1(a int, b int) bool {
	return a > 0
}

fn fil2(a string) bool {
	return a.len > 0
}