decorator pattern

Author: tensor-programming

decorator/main.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"sync"
+	"time"
+)
+
+type piFunc func(int) float64
+
+// logger(cache(Pi(n)))
+func wraplogger(fun piFunc, logger *log.Logger) piFunc {
+	return func(n int) float64 {
+		fn := func(n int) (result float64) {
+			defer func(t time.Time) {
+				logger.Printf("took=%v, n=%v, result=%v", time.Since(t), n, result)
+			}(time.Now())
+
+			return fun(n)
+		}
+		return fn(n)
+	}
+}
+
+// cache(logger(Pi(n)))
+func wrapcache(fun piFunc, cache *sync.Map) piFunc {
+	return func(n int) float64 {
+		fn := func(n int) float64 {
+			key := fmt.Sprintf("n=%d", n)
+			val, ok := cache.Load(key)
+			if ok {
+				return val.(float64)
+			}
+			result := fun(n)
+			cache.Store(key, result)
+			return result
+		}
+		return fn(n)
+	}
+}
+
+func Pi(n int) float64 {
+	ch := make(chan float64)
+
+	for k := 0; k <= n; k++ {
+		go func(ch chan float64, k float64) {
+			ch <- 4 * math.Pow(-1, k) / (2*k + 1)
+		}(ch, float64(k))
+	}
+
+	result := 0.0
+	for k := 0; k <= n; k++ {
+		result += <-ch
+	}
+
+	return result
+}
+
+func divide(n int) float64 {
+	return float64(n / 2)
+}
+
+func main() {
+	f := wrapcache(Pi, &sync.Map{})
+	g := wraplogger(f, log.New(os.Stdout, "Test ", 1))
+
+	g(100000)
+	g(20000)
+	g(100000)
+
+	f = wrapcache(divide, &sync.Map{})
+	g = wraplogger(f, log.New(os.Stdout, "Divide ", 1))
+
+	g(10000)
+	g(2000)
+	g(10)
+	g(10000)
+
+}