An example of how to range over collections with gypsy

gypsy-range.go

// Range runs the given closure on each element of the given list or map.  If
// the directive identifies a map, idx will be 0.  The index or key will be set
// to the appropriate values for a list or map, respectively, and the other
// will be zero.
//
// Example:
//   config.Range("servers", func(i int, _ string, n node) {
//     fmt.Printf("server[%d] = %q\n", i, n.(Scalar).String())
//   })
//   config.Range("users", func(_ int, name string, n node) {
//     fmt.Printf("user[%q] = %#v\n", name, n)
//   })
func Range(directive string, each func(idx int, key string, node yaml.Node)) error {
	node, err := yaml.Child(global.Root, directive)
	if err != nil {
		return fmt.Errorf("no such directive: %q: %s", directive, err)
	}

	switch n := node.(type) {
	case yaml.List:
		for i, v := range n {
			each(i, "", v)
		}
	case yaml.Map:
		for k, v := range n {
			each(0, k, v)
		}
	default:
		return fmt.Errorf("%q is not a sequence or mapping (%T)", directive, n)
	}
	return nil
}