Time for an 2014 update…

Task/Hailstone-sequence/Go/hailstone-sequence-1.go

@@ -2,8 +2,10 @@ package main
 
 import "fmt"
 
-func hs(n int, seq *[]int) {
-    s := append((*seq)[:0], n)
+// 1st arg is the number to generate the sequence for.
+// 2nd arg is a slice to recycle, to reduce garbage.
+func hs(n int, recycle []int) []int {
+    s := append(recycle[:0], n)
     for n > 1 {
         if n&1 == 0 {
             n = n / 2
@@ -12,21 +14,18 @@ func hs(n int, seq *[]int) {
         }
         s = append(s, n)
     }
-    *seq = s
+    return s
 }
 
 func main() {
-    var seq []int
-
-    hs(27, &seq)
+    seq := hs(27, nil)
     fmt.Printf("hs(27): %d elements: [%d %d %d %d ... %d %d %d %d]\n",
         len(seq), seq[0], seq[1], seq[2], seq[3],
         seq[len(seq)-4], seq[len(seq)-3], seq[len(seq)-2], seq[len(seq)-1])
 
     var maxN, maxLen int
     for n := 1; n < 100000; n++ {
-        // reusing seq reduces garbage
-        hs(n, &seq)
+        seq = hs(n, seq)
         if len(seq) > maxLen {
             maxN = n
             maxLen = len(seq)