first class function example

functions/first_class/main.go

@@ -0,0 +1,32 @@
+package main
+
+import "github.com/davecgh/go-spew/spew"
+
+type Cruncher func(int) int
+
+func mul(n int) int {
+	return n * 2
+}
+
+func add(n int) int {
+	return n + 100
+}
+
+func sub(n int) int {
+	return n - 1
+}
+
+func crunch(nums []int, a ...Cruncher) (rnums []int) {
+	rnums = append(rnums, nums...)
+	for _, f := range a {
+		for i, n := range rnums {
+			rnums[i] = f(n)
+		}
+	}
+	return
+}
+
+func main() {
+	nums := []int{1, 2, 3, 4, 5, 6}
+	spew.Dump(crunch(nums, mul, add, sub))
+}