#compdef newgrp

local expl groups

_wanted groups expl group || return 1

if ! _style -a groups groups groups; then
  (( $+_cache_groups )) ||
      if (( ${+commands[ypcat]} )); then
        : ${(A)_cache_groups:=${${(s: :)$(ypcat group.byname)}%%:*}} # If you use YP
      else
        : ${(A)_cache_groups:=${${(s: :)$(</etc/group)}%%:*}}
      fi

  groups=( "$_cache_groups[@]" )
fi

compadd "$@" "$expl[@]" - "$groups[@]"