more work on the parser

lib/expr.ml

@@ -0,0 +1,36 @@
+type literal = String of string | Number of float | Bool of bool | Nil
+(* [@@deriving show { with_path = false }] *)
+
+let show_literal literal =
+  match literal with
+  | String s -> s
+  | Number x -> string_of_float x
+  | Bool b -> string_of_bool b
+  | Nil -> "nil"
+
+type binary_op = Plus | Minus | Mul | Div | Equal | Less | Greater | LessEqual | GreaterEqual
+[@@deriving show { with_path = false }]
+
+type unary_op = Neg | Not [@@deriving show { with_path = false }]
+
+type expr =
+  | Literal of literal
+  | BinaryExpr of { op : binary_op; left : expr; right : expr }
+  | UnaryExpr of { op : unary_op; expr : expr }
+(* [@@deriving show { with_path = false }] *)
+
+let rec show_expr ?(indent = 0) expr =
+  let show_indented = show_expr ~indent:(indent + 2) in
+  let ident_s = String.make indent ' ' in
+  match expr with
+  | Literal literal -> ident_s ^ show_literal literal
+  | BinaryExpr { op; left; right } ->
+      ident_s ^ show_binary_op op ^ "\n" ^ show_indented left ^ "\n" ^ show_indented right
+  | UnaryExpr { op; expr } -> ident_s ^ show_unary_op op ^ "\n" ^ show_indented expr
+
+let make_string (s : string) = Literal (String s)
+let make_number (x : float) = Literal (Number x)
+let make_bool (b : bool) = Literal (Bool b)
+let make_nil () = Literal Nil
+let make_binary (op : binary_op) (left : expr) (right : expr) = BinaryExpr { op; left; right }
+let make_unary (op : unary_op) (expr : expr) = UnaryExpr { op; expr }