Poor man's option parser in bash

optparse.sh

#!/bin/bash

function opt_parse() {
  local _idx=1
  local _last=""
  while [ $_idx -lt $# ] || [ $_idx -eq $# ]; do
    _v=${!_idx}
    if [[ $_v == --* ]]; then
      local _name=$(echo $_v | tr - _)
      eval "__program_argument${_name}=::is-arg-set"
      _last=$_name
    else
      local e="__program_argument$_last"
      if [ -z "${!e}" ] || [ "${!e}" == "::is-arg-set" ]; then
        eval "__program_argument$_last=$_v"
      else
        eval "__program_argument$_last=${!e},$_v"
      fi
    fi
    let _idx=_idx+1
  done
}

function opt_get() {
  local _name=$(echo $1 | tr - _)
  local e="__program_argument$_name"
  if [ "${!e}" == "::is-arg-set" ]; then
    echo ""
  else
    echo ${!e}
  fi
}

function is_opt() {
  local _v=$(opt_get $1)
  if [ -n "$_v" ] || [ "$_v" == "::is-arg-set" ]; then
    return 0
  else
    return 1
  fi
}