string_cached is like string, except it uses of_utf8_bytes_cached.

Represent an ocaml array as an elisp list, without creating an intermediate ocaml list.

option represents None as nil and Some a as cons v nil, where v is the representation of a.

nil_or t represents None as nil and Some a as v, where v is the representation of a. This is a common representation used by Elisp functions. But it is only correct if nil is not a representation of any value in t; in that situation use Type.option.

Represent a tuple (a,b) as the elisp cons cell (a . b)

Represent a tuple (a,b) as the elisp list '(a b)

Embed a sexpable ocaml type, so we can save values of the type in emacs, e.g. as buffer local variables

A list of directories. Each element is a string (directory name) or nil (try default directory). nil values are converted to ".", which has the same meaning.