X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=code%2Funtyped_evaluator.ml;h=cf2a1b415f3dc1a822588c756af6acd98d0ba80d;hp=d820cce91b40a7b3faee9e0d3e1f80fa584d3f88;hb=e62e212f2cbd9d7a3468d5531a15fa1023ec14a6;hpb=02d40af51b0bf6ea346adf5856de5173a1540de1

diff --git a/code/untyped_evaluator.ml b/code/untyped_evaluator.ml
index d820cce9..cf2a1b41 100644
--- a/code/untyped_evaluator.ml
+++ b/code/untyped_evaluator.ml
@@ -2,7 +2,7 @@
    This is a simplified version of the code at ...
    You can use this code as follows:
 
-   1. First, use a text editor to fill in the uncompleted portions.
+   1. First, use a text editor to fill in the (* COMPLETE THIS *) portions
    2. Then see if OCaml will compile it, by typing `ocamlc -c untyped_evaluator.ml` in a Terminal.
    3. If it doesn't work, go back to step 1.
    4. If it does work, then you can start up the OCaml toplevel using `ocaml -I DIRECTORY`,
@@ -113,11 +113,11 @@ module V1 = struct
     | Var(var_ident) ->
         var_ident = ident
     | App(head, arg) ->
-        free_in ident head || free_in ident arg
+        (* COMPLETE THIS *)
     | Lambda(bound_ident, body) ->
-        bound_ident <> ident && free_in ident body
+        (* COMPLETE THIS *)
     | Let(bound_ident, arg, body) ->
-        free_in ident arg || (bound_ident <> ident && free_in ident body)
+        free_in ident arg || (* COMPLETE THIS *)
     | If(test, yes, no) ->
         free_in ident test || free_in ident yes || free_in ident no
     | Closure _ -> assert false 
@@ -205,7 +205,7 @@ module V1 = struct
         (match reduce_head_once arg env with
         | AlreadyResult _ ->
             (* if arg was not reducible, we can substitute *)
-            ReducedTo (substitute bound_var arg body)
+            (* COMPLETE THIS *)
         | StuckAt _ as outcome -> outcome (* propagate Stuck subterm *)
         | ReducedTo arg' -> ReducedTo (App(head, arg')))
   
@@ -214,12 +214,12 @@ module V1 = struct
         (match reduce_head_once head env with
         | AlreadyResult _ -> (* head was not reducible, was arg? *)
             (match reduce_head_once arg env with
-            | ReducedTo arg' -> ReducedTo (App(head, arg'))
+            | ReducedTo arg' -> (* COMPLETE THIS *)
             (* reducible cases of App(result, result) were caught above; so here we're stuck *)
             | AlreadyResult _ -> StuckAt term
             | StuckAt _ as outcome -> outcome) (* propagate Stuck subterm *)
         | StuckAt _ as outcome -> outcome (* propagate Stuck subterm *)
-        | ReducedTo head' -> ReducedTo (App(head', arg)))
+        | ReducedTo head' -> (* COMPLETE THIS *))
   
 
 
@@ -248,7 +248,7 @@ module V2 = struct
     | Var var ->
         (match lookup var env with
         (* Free variables will never be pushed to the env, so we can be
-	   sure this is a result. *) CHECK
+	   sure this is a result. *)
         | Some res -> res
         | None -> failwith ("Unbound variable `" ^ var ^ "`"))
 
@@ -265,8 +265,7 @@ module V2 = struct
 	   bound to the result of evaluating arg under the
            current env *)
         let arg' = eval arg env in
-        let env' = push bound_var arg' env in
-        eval body env'
+        let env' = (* COMPLETE THIS *)
 
     | App(head, arg) ->
         (match eval head env with
@@ -276,8 +275,7 @@ module V2 = struct
 	    (* evaluate body under saved_env to govern its free
 	       variables, except that we add a binding of
                bound_var to arg' *)
-            let saved_env' = push bound_var arg' saved_env in
-            eval body saved_env'
+            let saved_env' = (* COMPLETE THIS *)
         | head' -> raise (Stuck(App(head',arg))))