Booleans and if.

3 files changed, 40 insertions, 6 deletions

diff --git a/discocaml/ast.ml b/discocaml/ast.ml
index 025fa24..8e9c0c9 100644
--- a/discocaml/ast.ml
+++ b/discocaml/ast.ml
@@ -20,7 +20,9 @@ type 'a prim =
 
 and expr =
   | App of expr index * expr index
+  | Bool of bool
   | Cons of expr index * expr index
+  | If of expr index * expr index * expr index
   | Int of int
   | Lam of string * expr index
   | Let of bool * string * expr index * expr index
@@ -78,6 +80,8 @@ let add_expr_to_ast (ast : 'a ast) : Parsetree.expression -> expr index =
       ->
         add (Cons (loop hd, loop tl))
     | Pexp_construct ({ txt = Lident "[]"; _ }, None) -> add Nil
+    | Pexp_construct ({ txt = Lident "false"; _ }, None) -> add (Bool false)
+    | Pexp_construct ({ txt = Lident "true"; _ }, None) -> add (Bool true)
     | Pexp_fun (Nolabel, None, arg_pat, body) -> (
         match arg_pat.ppat_desc with
         | Ppat_var { txt = name; _ } -> add (Lam (name, loop body))
@@ -86,6 +90,8 @@ let add_expr_to_ast (ast : 'a ast) : Parsetree.expression -> expr index =
     | Pexp_ident { txt = Lident "-"; _ } -> binop Sub
     | Pexp_ident { txt = Lident "*"; _ } -> binop Mul
     | Pexp_ident { txt = Lident name; _ } -> add (Var name)
+    | Pexp_ifthenelse (cond, then_, Some else_) ->
+        add (If (loop cond, loop then_, loop else_))
     | Pexp_let
         ( recursive,
           [
@@ -153,6 +159,8 @@ let parsetree_of_subexpr (ast : 'a ast) : expr -> Parsetree.expression =
         let f, xs = list_of_apps expr in
         let xs = List.map (fun x -> (Asttypes.Nolabel, loop (subexpr x))) xs in
         Wrap.expression (Pexp_apply (loop f, xs))
+    | Bool b ->
+        Wrap.expression (Pexp_construct (Wrap.ident (string_of_bool b), None))
     | Cons (hd, tl) ->
         Wrap.expression
           (Pexp_construct
@@ -160,6 +168,12 @@ let parsetree_of_subexpr (ast : 'a ast) : expr -> Parsetree.expression =
                Some
                  (Wrap.expression
                     (Pexp_tuple [ loop (subexpr hd); loop (subexpr tl) ])) ))
+    | If (cond, then_, else_) ->
+        Wrap.expression
+          (Pexp_ifthenelse
+             ( loop (subexpr cond),
+               loop (subexpr then_),
+               Some (loop (subexpr else_)) ))
     | Int n ->
         Wrap.expression (Pexp_constant (Pconst_integer (Int.to_string n, None)))
     | Lam (x, b) ->
diff --git a/discocaml/draw_tree.ml b/discocaml/draw_tree.ml
index 3429a71..08a8288 100644
--- a/discocaml/draw_tree.ml
+++ b/discocaml/draw_tree.ml
@@ -7,10 +7,12 @@ let add_node (fmt : Format.formatter) (i : expr index) (expr : expr) : unit =
       Format.fprintf fmt
         "  expr%d [fontname=\"CMU Typewriter Text Bold\", label=\"apply\"];\n"
         i.index
+  | Bool b -> Format.fprintf fmt "  expr%d [label=\"%b\"];\n" i.index b
   | Cons _ ->
       Format.fprintf fmt
         "  expr%d [fontname=\"CMU Typewriter Text Bold\", label=\"::\"];\n"
         i.index
+  | If (_, _, _) -> Format.fprintf fmt "  expr%d [label=\"if\"];\n" i.index
   | Int n -> Format.fprintf fmt "  expr%d [label=\"%d\"];\n" i.index n
   | Lam _ -> Format.fprintf fmt "  expr%d [label=\"λ\"];\n" i.index
   | Let (recursive, _, _, _) ->
@@ -40,6 +42,10 @@ let add_expr_edges (ast : 'a ast) (fmt : Format.formatter)
     | Cons (hd, tl) ->
         edge_to hd;
         edge_to tl
+    | If (cond, then_, else_) ->
+        edge_to cond;
+        edge_to then_;
+        edge_to else_
     | Lam (x, b) ->
         Format.fprintf fmt "  expr%d -> expr%d_var;\n" i.index i.index;
         Format.fprintf fmt "  expr%d_var [label=%S];\n" i.index x;
@@ -59,7 +65,7 @@ let add_expr_edges (ast : 'a ast) (fmt : Format.formatter)
         edge_to l;
         edge_to r
     | Var _ -> ()
-    | Int _ | Nil -> ()
+    | Bool _ | Int _ | Nil -> ()
   in
   loop
 
diff --git a/discocaml/eval.ml b/discocaml/eval.ml
index 81709e6..f1e5a2b 100644
--- a/discocaml/eval.ml
+++ b/discocaml/eval.ml
@@ -9,10 +9,14 @@ let has_free_var (ast : expr ast) (i : expr index) (name : string) : bool =
     | App (f, x) ->
         loop f;
         loop x
+    | Bool _ | Int _ | Nil -> ()
     | Cons (hd, tl) ->
         loop hd;
         loop tl
-    | Int _ | Nil -> ()
+    | If (cond, then_, else_) ->
+        loop cond;
+        loop then_;
+        loop else_
     | Lam (x, b) -> if not (String.equal name x) then loop b
     | Let (recursive, name', bound, body) ->
         if not (String.equal name name') then loop body;
@@ -64,13 +68,15 @@ let check_redex (ast : expr ast) (i : expr index) : unit =
   match get_subexpr ast i with
   | App (f, _) -> (
       match get_subexpr ast f with Lam _ -> raise (FoundRedex i) | _ -> ())
+  | If (cond, _, _) -> (
+      match get_subexpr ast cond with Bool _ -> raise (FoundRedex i) | _ -> ())
   | Let (_, _, _, _) -> raise (FoundRedex i)
   | Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) -> (
       match (get_subexpr ast l, get_subexpr ast r) with
       | Int _, Int _ -> raise (FoundRedex i)
       | _ -> ())
   | Var _ -> ()
-  | Cons _ | Int _ | Lam _ | Nil -> ()
+  | Bool _ | Cons _ | Int _ | Lam _ | Nil -> ()
 
 let find_redex_cbv_in (ast : expr ast) : expr index -> unit =
   let rec loop (i : expr index) : unit =
@@ -78,12 +84,13 @@ let find_redex_cbv_in (ast : expr ast) : expr index -> unit =
     | App (f, x) ->
         loop f;
         loop x
+    | If (cond, _, _) -> loop cond
     | Let (_, _, bound, _) -> loop bound
     | Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) ->
         loop l;
         loop r
     | Var _ -> ()
-    | Cons _ | Int _ | Lam _ | Nil -> ());
+    | Bool _ | Cons _ | Int _ | Lam _ | Nil -> ());
     check_redex ast i
   in
   loop
@@ -95,12 +102,13 @@ let find_redex_cbn_in (ast : expr ast) : expr index -> unit =
     | App (f, x) ->
         loop f;
         loop x
+    | If (cond, _, _) -> loop cond
     | Let (_, _, _, body) -> loop body
     | Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) ->
         loop l;
         loop r
     | Var _ -> ()
-    | Cons _ | Int _ | Lam _ | Nil -> ()
+    | Bool _ | Cons _ | Int _ | Lam _ | Nil -> ()
   in
   loop
 
@@ -131,8 +139,9 @@ let subst (ast : expr ast) (from : string) (to_ : expr index) :
     in
     match get_subexpr ast i with
     | App (f, x) -> add (App (loop f, loop x))
+    | Bool _ | Int _ | Nil -> i
     | Cons (hd, tl) -> add (Cons (loop hd, loop tl))
-    | Int _ | Nil -> i
+    | If (cond, then_, else_) -> add (If (loop cond, loop then_, loop else_))
     | Lam (x, b) -> if String.equal from x then i else add (Lam (x, loop b))
     | Let (false, name, bound, body) ->
         add
@@ -156,6 +165,11 @@ let reduce (ast : expr ast) (i : expr index) : expr ast =
         match get_subexpr ast f with
         | Lam (x', b) -> get_subexpr ast (subst ast x' x b)
         | _ -> fail ())
+    | If (cond, then_, else_) -> (
+        match get_subexpr ast cond with
+        | Bool true -> get_subexpr ast then_
+        | Bool false -> get_subexpr ast else_
+        | _ -> fail ())
     | Let (_, name, _, body) when not (has_free_var ast body name) ->
         get_subexpr ast body
     | Let (recursive, name, bound, body) ->