Ocaml: Add step 4, but not str fns or optionals.

ocaml/core.ml

@@ -0,0 +1,32 @@
+let ns = Env.make None
+
+let num_fun t f = Types.Fn
+  (function
+    | [(Types.Int a); (Types.Int b)] -> t (f a b)
+    | _ -> raise (Invalid_argument "Numeric args required for this Mal builtin"))
+
+let mk_int x = Types.Int x
+let mk_bool x = Types.Bool x
+
+let init env = begin
+  Env.set env (Types.Symbol "+")  (num_fun mk_int  ( +  ));
+  Env.set env (Types.Symbol "-")  (num_fun mk_int  ( -  ));
+  Env.set env (Types.Symbol "*")  (num_fun mk_int  ( *  ));
+  Env.set env (Types.Symbol "/")  (num_fun mk_int  ( /  ));
+  Env.set env (Types.Symbol "<")  (num_fun mk_bool ( <  ));
+  Env.set env (Types.Symbol "<=") (num_fun mk_bool ( <= ));
+  Env.set env (Types.Symbol ">")  (num_fun mk_bool ( >  ));
+  Env.set env (Types.Symbol ">=") (num_fun mk_bool ( >= ));
+
+  Env.set env (Types.Symbol "list") (Types.Fn (function xs -> Types.MalList xs));
+  Env.set env (Types.Symbol "list?")
+    (Types.Fn (function [Types.MalList _] -> Types.Bool true | _ -> Types.Bool false));
+  Env.set env (Types.Symbol "empty?")
+    (Types.Fn (function [Types.MalList []] -> Types.Bool true | _ -> Types.Bool false));
+  Env.set env (Types.Symbol "count")
+    (Types.Fn (function [Types.MalList xs] -> Types.Int (List.length xs) | _ -> Types.Int 0));
+  Env.set env (Types.Symbol "=")
+    (Types.Fn (function [a; b] -> Types.Bool (a = b) | _ -> Types.Bool false));
+
+end
+

ocaml/step4_if_fn_do.ml

@@ -0,0 +1,67 @@
+let repl_env = Env.make (Some Core.ns)
+
+let rec eval_ast ast env =
+  match ast with
+    | Types.Symbol s -> Env.get env ast
+    | Types.MalList xs -> Types.MalList (List.map (fun x -> eval x env) xs)
+    | _ -> ast
+and eval ast env =
+  match ast with
+    | Types.MalList [(Types.Symbol "def!"); key; expr] ->
+        let value = (eval expr env) in
+          Env.set env key value; value
+    | Types.MalList [(Types.Symbol "let*"); (Types.MalList bindings); body] ->
+        (let sub_env = Env.make (Some env) in
+          let rec bind_pairs = (function
+            | sym :: expr :: more ->
+                Env.set sub_env sym (eval expr sub_env);
+                bind_pairs more
+            | _::[] -> raise (Invalid_argument "let* bindings must be an even number of forms")
+            | [] -> ())
+            in bind_pairs bindings;
+          eval body sub_env)
+    | Types.MalList ((Types.Symbol "do") :: body) ->
+        List.fold_left (fun x expr -> eval expr env) Types.Nil body
+    | Types.MalList [Types.Symbol "if"; test; then_expr; else_expr] ->
+        if Types.to_bool (eval test env) then (eval then_expr env) else (eval else_expr env)
+    | Types.MalList [Types.Symbol "if"; test; then_expr] ->
+        if Types.to_bool (eval test env) then (eval then_expr env) else Types.Nil
+    | Types.MalList [Types.Symbol "fn*"; Types.MalList arg_names; expr] ->
+        Types.Fn
+          (function args ->
+            let sub_env = Env.make (Some env) in
+              let rec bind_args = (fun a b ->
+                (match a, b with
+                  | [Types.Symbol "&"; name], args -> Env.set sub_env name (Types.MalList args);
+                  | (name :: names), (arg :: args) ->
+                      Env.set sub_env name arg;
+                      bind_args names args;
+                  | [], [] -> ()
+                  | _ -> raise (Invalid_argument "Bad param count in fn call")))
+              in (bind_args arg_names args);
+              eval expr sub_env)
+    | Types.MalList _ ->
+      (match eval_ast ast env with
+         | Types.MalList ((Types.Fn f) :: args) -> f args
+         | _ -> raise (Invalid_argument "Cannot invoke non-function"))
+    | _ -> eval_ast ast env
+
+let read str = Reader.read_str str
+let print exp = Printer.pr_str exp
+let rep str env = print (eval (read str) env)
+
+let rec main =
+  try
+    Core.init Core.ns;
+    ignore (rep "(def! not (fn* (a) (if a false true)))" repl_env);
+    while true do
+      print_string "user> ";
+      let line = read_line () in
+        try
+          print_endline (rep line repl_env);
+        with End_of_file -> ()
+         | Invalid_argument x ->
+             output_string stderr ("Invalid_argument exception: " ^ x ^ "\n");
+             flush stderr
+    done
+  with End_of_file -> ()