88 lines
2 KiB
OCaml
88 lines
2 KiB
OCaml
(* simple, untyped AST. *)
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type t =
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| Nothing
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| Nint of int
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| Nfloat of float
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| Nbool of bool
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| Nstring of string
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| Nsymbol of string
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| Nfunction of string * t
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| Nexternal of string
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| Var of string
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| Let of string * t
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| Letin of string * t * t
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| Unary of operator * t
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| Binop of t * operator * t
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| If of t * t * t (* cond then else *)
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| Apply of t * t list (* function application *)
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and operator =
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| Add | Sub | Mul | Div (* arithmetics *)
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| Mod (* modular operation *)
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| Exp (* exponentation *)
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| Eq | Neq | GE | LE | GT | LT
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| Negate
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let op_to_string = function
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| Add -> "+"
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| Sub -> "-"
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| Mul -> "*"
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| Div -> "/"
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| Mod -> "%"
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| Exp -> "^"
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| Eq -> "="
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| Neq -> "<>"
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| GE -> ">="
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| LE -> "<="
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| GT -> ">"
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| LT -> "<"
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| Negate -> "-"
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let unary op t =
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Unary (op, t)
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let binop left op right =
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Binop (left, op, right)
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(* print ast LISP style. *)
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let print ast =
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let rec cascade = function
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| Nfunction (arg, e) ->
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let args, e = cascade e in
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arg :: args, e
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| e -> [], e
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in
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let pr = Printf.printf in
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let rec aux = function
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| Nothing -> pr ""
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| Nint n -> pr "%d" n
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| Nfloat n -> pr "%f" n
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| Nbool b -> pr "%b" b
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| Nstring s -> pr "\"%s\"" s
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| Nsymbol s -> pr "#%s" s
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| Nfunction (arg, e) ->
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let args, e = cascade e in
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pr "(lambda (%s" arg;
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List.iter (pr " %s") args;
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pr ") "; aux e; pr ")"
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| Nexternal e -> pr "(extern %s)" e
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| Var v -> pr "%s" v
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| Let (v, e) ->
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pr "(define %s " v; aux e; pr ")"
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| Letin (v, e, f) ->
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pr "(let ((%s " v; aux e; pr ")) "; aux f; pr ")"
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| Unary (op, t) ->
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let op = op_to_string op in
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pr "(%s " op; aux t; pr ")"
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| Binop (left, op, right) ->
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let op = op_to_string op in
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pr "(%s " op; aux left; pr " "; aux right; pr ")"
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| If (co, th, el) ->
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let f e = pr " "; aux e in
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pr "(if"; f co; f th; f el; pr ")"
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| Apply (f, args) ->
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pr "("; aux f; List.iter (fun a -> pr " "; aux a) args; pr ")"
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in
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aux ast; pr "\n"
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