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(*===----------------------------------------------------------------------===
* Abstract Syntax Tree (aka Parse Tree)
*===----------------------------------------------------------------------===*)
(* expr - Base type for all expression nodes. *)
type expr =
(* variant for numeric literals like "1.0". *)
| Number of float
(* variant for referencing a variable, like "a". *)
| Variable of string
(* variant for a unary operator. *)
| Unary of char * expr
(* variant for a binary operator. *)
| Binary of char * expr * expr
(* variant for function calls. *)
| Call of string * expr array
(* variant for if/then/else. *)
| If of expr * expr * expr
(* variant for for/in. *)
| For of string * expr * expr * expr option * expr
(* proto - This type represents the "prototype" for a function, which captures
* its name, and its argument names (thus implicitly the number of arguments the
* function takes). *)
type proto =
| Prototype of string * string array
| BinOpPrototype of string * string array * int
(* func - This type represents a function definition itself. *)
type func = Function of proto * expr
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