go_playground/2-importpackage

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:

# 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.

cd ..
nano hello.go
>   package main
>   
>   import (
>   	"fmt"
>   
>   	"example/user/importpackage/importpackage"
>   )
>   
>   func main() {
>   	fmt.Println(importpackage.ReverseRunes("!oG ,olleH"))
>   }
go run hello.go