diff --git a/lib/compiler/core_ast.ml b/lib/compiler/core_ast.ml index 36e0d67..f64691b 100644 --- a/lib/compiler/core_ast.ml +++ b/lib/compiler/core_ast.ml @@ -14,9 +14,8 @@ type literal = type expression = | Literal of literal | Var of string - | Apply of expression * expression list - | Lambda of string list * expression - | Let of (string * expression) list * expression + | Apply of expression * expression + | Lambda of string * expression | LetRec of (string * expression) list * expression | If of expression * expression * expression | Set of string * expression @@ -37,12 +36,41 @@ and pair_of_binding = function | Syntactic_ast.LetBinding (s, e) -> (s, of_expr e) and pair_of_clause = function | Syntactic_ast.CondClause (e1, e2) -> (of_expr e1, of_expr e2) + +and make_lambda args body = + match args with + (* TODO: gensym here instead of using _ directly *) + | [] -> Lambda ("_", of_body body) + | x :: [] -> Lambda (x, of_body body) + | x :: xs -> Lambda (x, make_lambda xs body) + +and make_apply f args = + let rec aux f = function + | [] -> Apply (f, Literal Nil) + | arg :: [] -> Apply (f, arg) + | arg :: args -> aux (Apply (f, arg)) args + in aux f args +(* desugars this... + (let ((x 5) (y 4)) (f x y)) + ... into this... + (((lambda (x) (lambda (y) ((f x) y))) 5) 4) + *) +and make_let bs body = + let bs = List.map pair_of_binding bs in + let rec aux = function + | (s, e) :: rest -> + Apply (Lambda (s, aux rest), e) + | [] -> of_body body in + aux bs (* We convert a body into a regular letrec form. A body is defined as a series of definitions followed by a series of expressions. The definitions behave exactly as a letrec, so it makes sense to convert the body into a normal letrec. *) and of_body : Syntactic_ast.body Syntactic_ast.t -> expression = function + | Body ([], exprs) -> + let exprs = List.map of_expr exprs in + Begin exprs | Body (defs, exprs) -> let exprs = List.map of_expr exprs in let defs = List.map pair_of_def defs in @@ -61,8 +89,8 @@ and of_expr : Syntactic_ast.expression Syntactic_ast.t -> expression = function | LitString x -> Literal (String x) | Var x -> Var x | QuotedList _ -> failwith "TODO: rethink how quoted lists should work, the current definition makes no sense." - | Lambda (ll, b) -> Lambda (of_ll ll, of_body b) - | Let (bindings, b) -> Let (List.map pair_of_binding bindings, of_body b) + | Lambda (ll, b) -> make_lambda (of_ll ll) b + | Let (bindings, b) -> make_let bindings b | LetRec (bindings, b) -> LetRec (List.map pair_of_binding bindings, of_body b) | Cond (clauses) -> List.fold_right @@ -72,7 +100,7 @@ and of_expr : Syntactic_ast.expression Syntactic_ast.t -> expression = function | If (e1, e2, e3) -> If (of_expr e1, of_expr e2, of_expr e3) | Set (s, e) -> Set (s, of_expr e) - | Apply (f, es) -> Apply (of_expr f, List.map of_expr es) + | Apply (f, es) -> make_apply (of_expr f) (List.map of_expr es) and of_syntactic : Syntactic_ast.top_level -> top_level = function