use_ruby() {
  local ruby_root=$HOME/.ruby/$1
  load_prefix "$ruby_root"
  layout_ruby
}

check_env() {
  local ret=0; for var in "$@"; do [[ -v $var ]] || { echo "$var is missing"; ret=1; }; done; return $ret;
}

use_nvm() {
  local node_version=$1

  nvm_sh=~/.config/nvm/nvm.sh
  if [[ -e $nvm_sh ]]; then
    source $nvm_sh
    nvm use $node_version
  fi
}