Oh, whoops, I did not realize the attachments contained examples...
I suppose you could delay the commandRegistry assignment to be within
`func init()`
Attached is an example of this.
On 4/20/25 23:55, Wilgnert wrote:
Hey there! So, I was about to file a GitHub issue, but the prompt
suggested checking here first to avoid duplicates. I did a quick search
for "InvalidInitCycle" and "Invalid Init Cycle" in the history and came
up empty, so hopefully, this is a fresh report.
I'm tinkering with building a little REPL in Go. To handle commands, I
set up a map where the keys are the command names, and the values are
structs containing the command's name, a short description, and the
actual function to execute.
Now, to implement a "help" command, my first instinct was to just
iterate over this map and print out the name and description of each
command. However, the Go compiler threw a fit about this.
As a workaround, I came up with a bit of a convoluted solution. I
created a closure that captures my command map. This outer function then
returns another function, and /that/ inner function finally returns the
map. Surprisingly, the compiler was perfectly happy with this setup. It
compiled cleanly, and the "help" command in my REPL works exactly as I
intended. This closure trick feels a bit dirty, and I'm not entirely
sure if I'm inadvertently creating some memory leak.
What's really puzzling me is why the compiler would object to the direct
map iteration in the first place but be perfectly fine with this nested
function approach. Could someone shed some light on the underlying logic
here?
For reference, I'm using go version go1.24.2 linux/amd64.
Thanks in advance for any insights!
--
You received this message because you are subscribed to the Google
Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to golang-nuts+unsubscr...@googlegroups.com <mailto:golang-
nuts+unsubscr...@googlegroups.com>.
To view this discussion visit https://groups.google.com/d/msgid/golang-
nuts/96783b30-aa66-4db4-895a-d16ce3ff4807n%40googlegroups.com <https://
groups.google.com/d/msgid/golang-nuts/96783b30-aa66-4db4-895a-
d16ce3ff4807n%40googlegroups.com?utm_medium=email&utm_source=footer>.
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion visit
https://groups.google.com/d/msgid/golang-nuts/d8928111-f052-43a2-9917-74bd8d486bd3%40gmail.com.
package main
import (
"bufio"
"fmt"
"os"
"strings"
)
type cliCommand struct {
name string
description string
callback func() error
}
var commandRegistry map[string]cliCommand
func init() {
commandRegistry = map[string]cliCommand{
"help": {
name: "help",
description: "Displays a help message",
callback: commandHelp,
},
}
}
func commandHelp() error {
fmt.Println("Usage: ")
for _, v := range commandRegistry {
fmt.Printf("%v: %v\n", v.name, v.description)
}
return nil
}
func handleCommand(ss []string) {
command, ok := commandRegistry[ss[0]]
if !ok {
fmt.Printf("Unknown command: \"%v\"\n", ss[0])
return
}
err := command.callback()
if err != nil {
fmt.Println(fmt.Errorf("%w", err))
}
}
func main() {
REPL()
}
func REPL() {
scanner := bufio.NewScanner(os.Stdin)
for {
fmt.Print("> ")
if !scanner.Scan() {
break
}
in := scanner.Text()
clean := cleanInput(in)
if len(clean) == 0 {
continue
}
handleCommand(clean)
}
}
func cleanInput(text string) []string {
var ss []string
lowered_text := strings.ToLower(text)
for _, s := range strings.Split(lowered_text, " ") {
s = strings.Trim(s, " \n\t\v\f\r")
if len(s) != 0 {
ss = append(ss, s)
}
}
return ss
}
