catala/src/catala/default_calculus/ast.ml

(* This file is part of the Catala compiler, a specification language for tax and social benefits
   computation rules. Copyright (C) 2020 Inria, contributor: Denis Merigoux
   <denis.merigoux@inria.fr>

   Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
   in compliance with the License. You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software distributed under the License
   is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   or implied. See the License for the specific language governing permissions and limitations under
   the License. *)

module Pos = Utils.Pos
module Uid = Utils.Uid

(** Abstract syntax tree for the default calculus *)

(** {1 Abstract syntax tree} *)

type typ_lit = TBool | TUnit | TInt | TRat | TMoney | TDate | TDuration

type typ =
  | TLit of typ_lit
  | TTuple of typ Pos.marked list
  | TEnum of typ Pos.marked list
  | TArrow of typ Pos.marked * typ Pos.marked

type date = ODate.Unix.t

type duration = Z.t

type lit =
  | LBool of bool
  | LEmptyError
  | LInt of Z.t
  | LRat of Q.t
  | LMoney of Z.t
  | LUnit
  | LDate of date
  | LDuration of duration

type op_kind =
  | KInt
  | KRat
  | KMoney
  | KDate
  | KDuration  (** All ops don't have a Kdate and KDuration *)

type binop =
  | And
  | Or
  | Add of op_kind
  | Sub of op_kind
  | Mult of op_kind
  | Div of op_kind
  | Lt of op_kind
  | Lte of op_kind
  | Gt of op_kind
  | Gte of op_kind
  | Eq
  | Neq

type log_entry = VarDef | BeginCall | EndCall

type unop =
  | Not
  | Minus of op_kind
  | ErrorOnEmpty
  | Log of log_entry * Utils.Uid.MarkedString.info list

type operator = Binop of binop | Unop of unop

(** The expressions use the {{:https://lepigre.fr/ocaml-bindlib/} Bindlib} library, based on
    higher-order abstract syntax*)
type expr =
  | EVar of expr Bindlib.var Pos.marked
  | ETuple of (expr Pos.marked * Uid.MarkedString.info option) list
      (** The [MarkedString.info] is the former struct field name*)
  | ETupleAccess of expr Pos.marked * int * Uid.MarkedString.info option
      (** The [MarkedString.info] is the former struct field name*)
  | EInj of expr Pos.marked * int * Uid.MarkedString.info * typ Pos.marked list
      (** The [MarkedString.info] is the former enum case name *)
  | EMatch of expr Pos.marked * (expr Pos.marked * Uid.MarkedString.info) list
      (** The [MarkedString.info] is the former enum case name *)
  | ELit of lit
  | EAbs of Pos.t * (expr, expr Pos.marked) Bindlib.mbinder * typ Pos.marked list
  | EApp of expr Pos.marked * expr Pos.marked list
  | EAssert of expr Pos.marked
  | EOp of operator
  | EDefault of expr Pos.marked list * expr Pos.marked * expr Pos.marked
  | EIfThenElse of expr Pos.marked * expr Pos.marked * expr Pos.marked

(** {1 Variable helpers} *)

module Var = struct
  type t = expr Bindlib.var

  let make (s : string Pos.marked) : t =
    Bindlib.new_var
      (fun (x : expr Bindlib.var) : expr -> EVar (x, Pos.get_position s))
      (Pos.unmark s)

  let compare x y = Bindlib.compare_vars x y
end

module VarMap = Map.Make (Var)

type vars = expr Bindlib.mvar

let make_var ((x, pos) : Var.t Pos.marked) : expr Pos.marked Bindlib.box =
  Bindlib.box_apply (fun x -> (x, pos)) (Bindlib.box_var x)

let make_abs (xs : vars) (e : expr Pos.marked Bindlib.box) (pos_binder : Pos.t)
    (taus : typ Pos.marked list) (pos : Pos.t) : expr Pos.marked Bindlib.box =
  Bindlib.box_apply (fun b -> (EAbs (pos_binder, b, taus), pos)) (Bindlib.bind_mvar xs e)

let make_app (e : expr Pos.marked Bindlib.box) (u : expr Pos.marked Bindlib.box list) (pos : Pos.t)
    : expr Pos.marked Bindlib.box =
  Bindlib.box_apply2 (fun e u -> (EApp (e, u), pos)) e (Bindlib.box_list u)

let make_let_in (x : Var.t) (tau : typ Pos.marked) (e1 : expr Pos.marked Bindlib.box)
    (e2 : expr Pos.marked Bindlib.box) : expr Pos.marked Bindlib.box =
  Bindlib.box_apply2
    (fun e u -> (EApp (e, u), Pos.get_position (Bindlib.unbox e2)))
    (make_abs
       (Array.of_list [ x ])
       e2
       (Pos.get_position (Bindlib.unbox e2))
       [ tau ]
       (Pos.get_position (Bindlib.unbox e2)))
    (Bindlib.box_list [ e1 ])

type binder = (expr, expr Pos.marked) Bindlib.binder