Merge pull request #564 from devlights/add-gocollective-example

Author: devlights

examples/gocollective/concatenate-strings/Taskfile.yml

@@ -0,0 +1,6 @@
+version: '3'
+
+tasks:
+  run:
+    cmds:
+      - go run -race main.go

examples/gocollective/concatenate-strings/main.go

@@ -0,0 +1,50 @@
+// Stackoverflow Go Collective example
+//
+// How to efficiently concatenate strings in go
+//
+// URL
+//   - https://stackoverflow.com/questions/1760757/how-to-efficiently-concatenate-strings-in-go
+//
+// REFERENCES
+//   - https://pkg.go.dev/strings@latest#Builder
+//   - https://yourbasic.org/golang/measure-execution-time/
+package main
+
+import (
+	"bytes"
+	"log"
+	"strings"
+	"time"
+
+	"github.com/devlights/gomy/times"
+)
+
+func init() {
+	log.SetFlags(0)
+}
+
+func main() {
+	// Go 1.10 より strings.Builder が追加された。
+	// bytes.Buffer でも良いが、文字列の場合はこちらのほうが効率が良い。
+
+	var (
+		sb  strings.Builder
+		buf bytes.Buffer
+	)
+
+	// ----- bytes.Buffer ----- //
+	elapsed := times.Stopwatch(func(start time.Time) {
+		for i := 0; i < 3_000_000; i++ {
+			buf.WriteString("i")
+		}
+	})
+	log.Printf("[bytes.Buffer   ] len=%d, elapsed=%v", buf.Len(), elapsed)
+
+	// ----- strings.Builder ----- //
+	elapsed = times.Stopwatch(func(start time.Time) {
+		for i := 0; i < 3_000_000; i++ {
+			sb.WriteString("i")
+		}
+	})
+	log.Printf("[strings.Builder] len=%d, elapsed=%v", sb.Len(), elapsed)
+}

go.mod

@@ -3,7 +3,7 @@ module github.com/devlights/try-golang
 go 1.18
 
 require (
-	github.com/devlights/gomy v0.4.6
+	github.com/devlights/gomy v0.4.8
 	golang.org/x/crypto v0.0.0-20220214200702-86341886e292
 	golang.org/x/exp v0.0.0-20220518171630-0b5c67f07fdf
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c

go.sum

@@ -1,5 +1,5 @@
-github.com/devlights/gomy v0.4.6 h1:S/UiHgNF1/dF/MRhxgOT1Bsd5i33/Ly9qOSePU3Q7KU=
-github.com/devlights/gomy v0.4.6/go.mod h1:s6/L0jEn7J/F1bIRNu3nkf+Lz/n24RClTxD76DhqGEU=
+github.com/devlights/gomy v0.4.8 h1:LLWJssPBc/ZG29iPRxzPep5dJvSCcc1zkue4LFaLhuE=
+github.com/devlights/gomy v0.4.8/go.mod h1:s6/L0jEn7J/F1bIRNu3nkf+Lz/n24RClTxD76DhqGEU=
 golang.org/x/crypto v0.0.0-20220214200702-86341886e292 h1:f+lwQ+GtmgoY+A2YaQxlSOnDjXcQ7ZRLWOHbC6HtRqE=
 golang.org/x/crypto v0.0.0-20220214200702-86341886e292/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/exp v0.0.0-20220518171630-0b5c67f07fdf h1:oXVg4h2qJDd9htKxb5SCpFBHLipW6hXmL3qpUixS2jw=