From 956f2b3ca5c33774fd70140d15a036e7d8545786 Mon Sep 17 00:00:00 2001
From: Robert Jeutter <robert.jeutter@gmx.de>
Date: Thu, 30 Dec 2021 20:34:53 +0100
Subject: [PATCH] import package project

---
 2-importpackage/go.mod                   |  3 ++
 2-importpackage/hello.go                 | 11 ++++++
 2-importpackage/importpackage/reverse.go | 12 ++++++
 2-importpackage/readme.md                | 50 ++++++++++++++++++++++++
 4 files changed, 76 insertions(+)
 create mode 100644 2-importpackage/go.mod
 create mode 100644 2-importpackage/hello.go
 create mode 100644 2-importpackage/importpackage/reverse.go
 create mode 100644 2-importpackage/readme.md

diff --git a/2-importpackage/go.mod b/2-importpackage/go.mod
new file mode 100644
index 0000000..7b45b4b
--- /dev/null
+++ b/2-importpackage/go.mod
@@ -0,0 +1,3 @@
+module example/user/importpackage
+
+go 1.17
diff --git a/2-importpackage/hello.go b/2-importpackage/hello.go
new file mode 100644
index 0000000..8dc7f45
--- /dev/null
+++ b/2-importpackage/hello.go
@@ -0,0 +1,11 @@
+package main
+
+import (
+	"fmt"
+
+	"example/user/importpackage/importpackage"
+)
+
+func main() {
+	fmt.Println(importpackage.ReverseRunes("!oG ,olleH"))
+}
\ No newline at end of file
diff --git a/2-importpackage/importpackage/reverse.go b/2-importpackage/importpackage/reverse.go
new file mode 100644
index 0000000..743724a
--- /dev/null
+++ b/2-importpackage/importpackage/reverse.go
@@ -0,0 +1,12 @@
+// Package importpackage implements additional functions to manipulate UTF-8
+// encoded strings, beyond what is provided in the standard "strings" package.
+package importpackage
+
+// ReverseRunes returns its argument string reversed rune-wise left to right.
+func ReverseRunes(s string) string {
+	r := []rune(s)
+	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+	return string(r)
+}
\ No newline at end of file
diff --git a/2-importpackage/readme.md b/2-importpackage/readme.md
new file mode 100644
index 0000000..1390660
--- /dev/null
+++ b/2-importpackage/readme.md
@@ -0,0 +1,50 @@
+# Import package
+write a `importpackage` package and use it from the hello program. 
+
+Because the `ReverseRunes` function begins with an upper-case letter, it is exported and can be used in other packages that import the importpackage package. 
+
+Test that the package compiles with go build:
+```bash
+# init project
+mkdir 2-importpackage
+cd 2-importpackage
+go mod init example/user/importpackage
+# create files
+touch hello.go
+mkdir importpackage
+cd importpackage
+nano reverse.go
+>   // Package importpackage implements additional functions to manipulate UTF-8
+>   // encoded strings, beyond what is provided in the standard "strings" package.
+package importpackage
+>   
+>   // ReverseRunes returns its argument string reversed rune-wise left to right.
+>   func ReverseRunes(s string) string {
+>   	r := []rune(s)
+>   	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+>   		r[i], r[j] = r[j], r[i]
+>   	}
+>   	return string(r)
+>   }
+go build
+```
+
+This won't produce an output file. Instead it saves the compiled package in the local build cache.
+
+After confirming that the importpackage package builds, use it from the `hello` program.
+```bash
+cd ..
+nano hello.go
+>   package main
+>   
+>   import (
+>   	"fmt"
+>   
+>   	"example/user/importpackage/importpackage"
+>   )
+>   
+>   func main() {
+>   	fmt.Println(importpackage.ReverseRunes("!oG ,olleH"))
+>   }
+go run hello.go
+```