Buffers and strings with range-indexed metadata is also how Emacs's text properties work. For example, this shows the print syntax for strings with properties:

Buffers and strings with range-indexed metadata is also how Emacs's text properties work. For example, this shows the print syntax for strings with properties: (concat (propertize "foo" 'face '(:weight bold)) " " (propertize "bar" 'link "http://bar")) ;;=> #("foo bar" 0 3 (face (:weight bold)) 4 7 (link "http://bar"))