package lambda

func Rename(e Expression, target string, substitute string) {
	switch e := e.(type) {
	case *Variable:
		if e.Value == target {
			e.Value = substitute
		}
	case *Abstraction:
		if e.Parameter == target {
			e.Parameter = substitute
		}

		Rename(e.Body, target, substitute)
	case *Application:
		Rename(e.Abstraction, target, substitute)
		Rename(e.Argument, target, substitute)
	}
}