diff options
Diffstat (limited to '')
| -rw-r--r-- | lib/term.ml | 15 | ||||
| -rw-r--r-- | lib/term.mli | 9 |
2 files changed, 24 insertions, 0 deletions
diff --git a/lib/term.ml b/lib/term.ml index a0dc760..fcef6f9 100644 --- a/lib/term.ml +++ b/lib/term.ml @@ -2,6 +2,7 @@ type t = | Integer of Z.t | Rational of Q.t | String of string + | Reference of string | Nil | Record of t Label.Map.t @@ -9,6 +10,16 @@ let integer z = Integer z let string s = String s let nil = Nil +let reference name = + let is_letter c = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') in + let is_body c = is_letter c || (c >= '0' && c <= '9') || c = '_' in + if + String.length name > 0 + && is_letter name.[0] + && String.for_all is_body name + then Ok (Reference name) + else Error (`Invalid_reference name) + let rational ~num ~den = if Z.equal den Z.zero then Error `Zero_denominator else @@ -52,6 +63,7 @@ let rec compare a b = | Integer x, Integer y -> Z.compare x y | Rational x, Rational y -> Q.compare x y | String x, String y -> String.compare x y + | Reference x, Reference y -> String.compare x y | Nil, Nil -> 0 | Record x, Record y -> Label.Map.compare compare x y | Integer _, _ -> -1 @@ -60,6 +72,8 @@ let rec compare a b = | _, Rational _ -> 1 | String _, _ -> -1 | _, String _ -> 1 + | Reference _, _ -> -1 + | _, Reference _ -> 1 | Nil, _ -> -1 | _, Nil -> 1 @@ -81,6 +95,7 @@ let rec pp fmt t = | Integer z -> Z.pp_print fmt z | Rational q -> Q.pp_print fmt q | String s -> Format.fprintf fmt "%S" s + | Reference name -> Format.fprintf fmt "#%s" name | Nil -> Format.pp_print_string fmt "#()" | Record map -> ( match as_cell t with diff --git a/lib/term.mli b/lib/term.mli index cf79d89..8dc201e 100644 --- a/lib/term.mli +++ b/lib/term.mli @@ -17,6 +17,11 @@ type t = private its minimal shape, so integer membership inclusion holds literally. *) | String of string + | Reference of string + (** A relation reference, written [#Name]: a first-class + value denoting a relation by name, resolved through the + catalog of a state. Distinct from {!String} on purpose; + identity is not representation. *) | Nil (** The empty sequence, written [#()]. *) | Record of t Label.Map.t (** A nonempty labeled tuple. Attribute order is canonical @@ -30,6 +35,10 @@ val nil : t (** The empty sequence, [#()]. The distinguished base every {!sequence} chain ends in. *) +val reference : string -> (t, [ `Invalid_reference of string ]) result +(** A relation reference. Validates the name: a letter, then + letters, digits, or underscores. *) + val rational : num:Z.t -> den:Z.t -> (t, [ `Zero_denominator ]) result (** Normalizes on entry: reduces by the gcd, moves the sign to the numerator, and collapses to {!Integer} when the reduced |