1(*===----------------------------------------------------------------------===
2 * Abstract Syntax Tree (aka Parse Tree)
3 *===----------------------------------------------------------------------===*)
4
5(* expr - Base type for all expression nodes. *)
6type expr =
7  (* variant for numeric literals like "1.0". *)
8  | Number of float
9
10  (* variant for referencing a variable, like "a". *)
11  | Variable of string
12
13  (* variant for a unary operator. *)
14  | Unary of char * expr
15
16  (* variant for a binary operator. *)
17  | Binary of char * expr * expr
18
19  (* variant for function calls. *)
20  | Call of string * expr array
21
22  (* variant for if/then/else. *)
23  | If of expr * expr * expr
24
25  (* variant for for/in. *)
26  | For of string * expr * expr * expr option * expr
27
28(* proto - This type represents the "prototype" for a function, which captures
29 * its name, and its argument names (thus implicitly the number of arguments the
30 * function takes). *)
31type proto =
32  | Prototype of string * string array
33  | BinOpPrototype of string * string array * int
34
35(* func - This type represents a function definition itself. *)
36type func = Function of proto * expr
37