YAPC::EU 2018 Glasgow Update!

Task/First-class-environments/Go/first-class-environments.go

@@ -0,0 +1,59 @@
+package main
+
+import "fmt"
+
+const jobs = 12
+
+type environment struct{ seq, cnt int }
+
+var (
+    env      [jobs]environment
+    seq, cnt *int
+)
+
+func hail() {
+    fmt.Printf("% 4d", *seq)
+    if *seq == 1 {
+        return
+    }
+    (*cnt)++
+    if *seq&1 != 0 {
+        *seq = 3*(*seq) + 1
+    } else {
+        *seq /= 2
+    }
+}
+
+func switchTo(id int) {
+    seq = &env[id].seq
+    cnt = &env[id].cnt
+}
+
+func main() {
+    for i := 0; i < jobs; i++ {
+        switchTo(i)
+        env[i].seq = i + 1
+    }
+
+again:
+    for i := 0; i < jobs; i++ {
+        switchTo(i)
+        hail()
+    }
+    fmt.Println()
+
+    for j := 0; j < jobs; j++ {
+        switchTo(j)
+        if *seq != 1 {
+            goto again
+        }
+    }
+    fmt.Println()
+
+    fmt.Println("COUNTS:")
+    for i := 0; i < jobs; i++ {
+        switchTo(i)
+        fmt.Printf("% 4d", *cnt)
+    }
+    fmt.Println()
+}