function padd --description 'add nix packages to PATH temporarily'
  for pkg in $argv
     set --local out $(nix-build '<nixpkgs>' --attr "$pkg.out" --no-out-link --quiet)
     set --local bin $out/bin
     if ! path is --type dir $bin
       echo "$bin doesn't exist"
     else
       fish_add_path --global $bin
       echo "$bin"
     end
  end
end