AStat/frontend/abstract_syntax_tree.ml

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2024-05-29 11:47:47 +02:00
(*
Cours "Sémantique et Application à la Vérification de programmes"
Antoine Miné 2015
Marc Chevalier 2018
Josselin Giet 2021
Ecole normale supérieure, Paris, France / CNRS / INRIA
*)
(*
Definition of the abstract syntax trees output by the parser.
*)
(* position in the source file, we use ocamllex's default type *)
type position = Lexing.position
let position_unknown = Lexing.dummy_pos
(* extents are pairs of positions *)
type extent = position * position (* start/end *)
let extent_unknown = (position_unknown, position_unknown)
(* Many parts of the syntax are tagged with an extent indicating which
part of the parser-file corresponds to the sub-tree.
This is very useful for interesting error reporting!
*)
type 'a ext = 'a * extent
(* variable identifiers are string *)
type id = string
(* types of variables: only int for now *)
type typ =
(* mathematical integers, in Z *)
| AST_TYP_INT
(* unary expression operators *)
type int_unary_op =
| AST_UNARY_PLUS (* +e *)
| AST_UNARY_MINUS (* -e *)
type bool_unary_op =
| AST_NOT (* !e logical negation *)
(* binary expression operators *)
type int_binary_op =
| AST_PLUS (* e + e *)
| AST_MINUS (* e - e *)
| AST_MULTIPLY (* e * e *)
| AST_DIVIDE (* e / e *)
| AST_MODULO (* e % e *)
type compare_op =
| AST_EQUAL (* e == e *)
| AST_NOT_EQUAL (* e != e *)
| AST_LESS (* e < e *)
| AST_LESS_EQUAL (* e <= e *)
| AST_GREATER (* e > e *)
| AST_GREATER_EQUAL (* e >= e *)
let reverse c = match c with
| AST_LESS -> AST_GREATER
| AST_GREATER -> AST_LESS
| AST_LESS_EQUAL -> AST_GREATER_EQUAL
| AST_GREATER_EQUAL -> AST_LESS_EQUAL
| x -> x
let negate c = match c with
| AST_LESS -> AST_GREATER_EQUAL
| AST_GREATER -> AST_LESS_EQUAL
| AST_LESS_EQUAL -> AST_GREATER
| AST_GREATER_EQUAL -> AST_LESS
| AST_EQUAL -> AST_NOT_EQUAL
| AST_NOT_EQUAL -> AST_EQUAL
type bool_binary_op =
| AST_AND (* e && e *)
| AST_OR (* e || e *)
(* expressions *)
type int_expr =
(* unary operation *)
| AST_int_unary of int_unary_op * (int_expr ext)
(* binary operation *)
| AST_int_binary of int_binary_op * (int_expr ext) * (int_expr ext)
(* variable use *)
| AST_int_identifier of id ext
(* constants (integers are still in their string representation) *)
| AST_int_const of string ext
(* non-deterministic choice between two integers *)
| AST_int_rand of (string ext) (* lower bound *) *
(string ext) (* upper bound *)
(* calls a function with arguments and return value *)
| AST_expr_call of (id ext) (* function name *) *
(int_expr ext list) (* arguments *)
type bool_expr =
(* unary operation *)
| AST_bool_unary of bool_unary_op * (bool_expr ext)
(* binary operation *)
| AST_bool_binary of bool_binary_op * (bool_expr ext) * (bool_expr ext)
| AST_compare of compare_op * (int_expr ext) * (int_expr ext)
(* constants *)
| AST_bool_const of bool
(* non-deterministic choice *)
| AST_bool_rand
(* statements *)
type stat =
(* block of statements { ... } *)
| AST_block of stat ext list
(* assignment lvalue = expr *)
| AST_assign of (id ext) * (int_expr ext)
(* assignment lvalue op= expr *)
| AST_assign_op of (id ext) * int_binary_op * (int_expr ext)
(* increment lvalue += cst *)
| AST_increment of (id ext) * int
(* if-then-else; the else branch is optional *)
| AST_if of (bool_expr ext) (* condition *) *
(stat ext) (* then branch *) *
(stat ext option) (* optional else *)
(* while loop *)
| AST_while of (bool_expr ext) (* condition *) *
(stat ext) (* body *)
(* for loop *)
| AST_for of (stat ext list) (* init *) *
(bool_expr ext option) (* condition *) *
(stat ext list) (* increment *) *
(stat ext) (* body *)
(* assertion: fail if the boolean expression does not hold *)
| AST_assert of bool_expr ext
(* declaration of a local variable, live until the end of the current block *)
| AST_local_decl of var_decl ext
(* calls a function with arguments (no return value) *)
| AST_stat_call of (id ext) (* function name *) *
(int_expr ext list) (* arguments *)
(* exits form the function, with optional return value *)
| AST_return of int_expr ext option
(* exits from the innermost while loop *)
| AST_break of unit ext
(* empty instruction: do nothing *)
| AST_SKIP
(* go to a label in the function *)
| AST_goto of id ext
(* destination of a goto *)
| AST_label of id ext
(* declare some variables with a common type *)
and var_decl = (typ ext) (* type *) * (var_init list) (* variable list *)
(* each declared variable has an optional initializer *)
and var_init = (id ext) (* declared variable *) *
(int_expr ext option) (* initializer *)
(* function declaration
(no return type, all functions return void)
*)
type fun_decl =
{ (* function name *)
fun_name: id ext;
(* formal arguments, with type *)
fun_args: ((typ ext) * (id ext)) list;
(* type of the returned value, if any *)
fun_typ: typ option ext;
(* function body *)
fun_body: stat ext list;
(* function location *)
fun_ext: extent;
}
(* top-level statements *)
type toplevel =
(* global variable declaration *)
| AST_global_decl of var_decl ext
(* function declaration *)
| AST_fun_decl of fun_decl ext
(* a program is a list of top-level statements *)
type prog = toplevel list ext