(** Attribute labels.

    A label names an attribute of a record or a relation schema,
    written [name:] in Sol source. Labels are the keys of every
    {!Term.t} record, so the whole term algebra sits on them. *)

type t
(** A validated label. Values of this type always hold a well-formed
    label name, by construction. *)

val of_string : string -> (t, [ `Invalid_label of string ]) result
(** The only way in. A well-formed label starts with a lowercase
    letter, followed by letters, digits, or underscores. Everything
    that builds or looks up record attributes goes through labels
    made here. *)

val to_string : t -> string
(** The label name, without the colon. *)

val equal : t -> t -> bool

val compare : t -> t -> int
(** Total order on names. Gives records a canonical attribute order
    regardless of how the source spelled them, which {!Term.equal}
    and content addressing rely on. *)

val pp : Format.formatter -> t -> unit
(** Prints [name:], as in Sol source. *)

module Map : Map.S with type key = t
(** Attribute maps, used by {!Term.t} records. *)