Example

import loki, strutils # `options` helpers (isSome/get/...) come from loki

loki(myHandler, input):
  do_greet name:
   ## Get a nice greeting!
   if isSome(name):
    echo("Hello ", name.get, "!")
   else:
    echo("Hello there!")
  do_add num1, num2:
    if isSome(num1) and isSome(num2):
      echo("Result is ", parseInt(num1.get) + parseInt(num2.get))
    else:
      echo("Provide two numbers to add them")
  do_EOF:
    write(stdout, "Bye!\n")
    return true
  default:
    write(stdout, "*** Unknown syntax: ", input.text , " ***\n")

let myCmd = newLoki(
  handler=myHandler,
  intro="Welcome to my CLI!\n",
)

myCmd.cmdLoop

proc do_greet(line: Line; name: Option[string] = none(string)): bool =
  ## Get a nice greeting!
  if isSome(name):
    echo("Hello ", get(name), "!")
  else:
    echo("Hello there!")

proc do_add(line: Line; num1: Option[string] = none(string);
            num2: Option[string] = none(string)): bool =
  if isSome(num1) and isSome(num2):
    echo("Result is ", parseInt(get(num1)) + parseInt(get(num2)))
  else:
    echo("Provide two numbers to add them")

proc do_EOF(line: Line): bool =
  write(stdout, "Bye!\n")
  return true

proc default(line: Line): bool =
  write(stdout, "*** Unknown syntax: ", line.text, " ***\n")

# Auto-generated. The command lists and docs are known at compile time, so they
# are baked in as literals -- the generated code needs no extra imports.
proc help(input: Line): bool =
  if isSome(input.args):
    let cmdarg = pick(input.args, 0)
    if isSome(cmdarg):
      let cmd = get(cmdarg)
      let docced = @["greet"]
      let docs = @["Get a nice greeting!"]
      let undocced = @["add"]
      if cmd in undocced:
        writeLine(stdout, "*** No help for this command")
      else:
        for i in 0 ..< docced.len:
          if cmd == docced[i]:
            writeLine(stdout, docs[i])
            break
      return
  write(stdout, "\nDocumented commands (type help <topic>):\n")
  write(stdout, "========================================\n")
  write(stdout, "greet")
  write(stdout, "\n\nUndocumented commands:\n")
  write(stdout, "======================\n")
  write(stdout, "add")
  write(stdout, "\n")

proc myHandler(line: Line): bool =
  case line.command
  of "greet":
    if isSome(line.args):
      return do_greet(line, pick(line.args, 0))
    else:
      return do_greet(line, none(string))
  of "add":
    if isSome(line.args):
      return do_add(line, pick(line.args, 0), pick(line.args, 1))
    else:
      return do_add(line, none(string), none(string))
  of "EOF":
    return do_EOF(line)
  of "help":
    return help(line)
  else:
    return default(line)