From 2e5e691cfe84ac2162e22797b63c2066bfef6173 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Mon, 22 Jan 2018 12:29:59 +0100
Subject: [PATCH] First try for defun, produces bad code

Block variables accessed out of scope
---
 src/Defun.ml | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 99 insertions(+), 1 deletion(-)

diff --git a/src/Defun.ml b/src/Defun.ml
index 7264dac..d464136 100644
--- a/src/Defun.ml
+++ b/src/Defun.ml
@@ -3,5 +3,103 @@ module S = Tail
 (* The target calculus. *)
 module T = Top
 
+module IMap = Map.Make(struct type t = int let compare = compare end)
+
+exception InconsistentFuncState of int
+(** Thrown when somehow, the two parts of a [funcState] are inconsistent. The
+ * parameter is the arity at which the two parts diverged. *)
+
+let freshTag =
+    let count = ref 0 in
+    fun () ->
+        incr count;
+        !count
+
+(** Function state handling *)
+
+type applyFunc = ApplyFunc of T.variable * T.variable list
+type funcArityList = (T.branch list) IMap.t
+type applyArityMap = applyFunc IMap.t
+type funcState = FuncState of applyArityMap * funcArityList
+
+let empty_fs = FuncState(IMap.empty, IMap.empty)
+
+let get_apply (FuncState(applyMap, funcList) as fs) arity =
+    let rec list_init f n acc = match n with
+    | 0 -> acc
+    | n -> list_init f (n-1) ((f (n-1)) :: acc) in
+
+    let new_apply () =
+        let name = Atom.fresh ("apply" ^ (string_of_int arity) ^ "_") in
+        let args = list_init (function
+            | 0 -> Atom.fresh "fct_"
+            | n -> Atom.fresh ("arg" ^ (string_of_int n) ^ "_"))
+            arity [] in
+        ApplyFunc(name, args)
+    in
+    try
+        IMap.find arity applyMap, fs
+    with Not_found ->
+        let newArityFct = new_apply () in
+        newArityFct, FuncState(IMap.add arity newArityFct applyMap, funcList)
+
+let add_func (FuncState(applyMap, funcList)) arity fct =
+    let cList = try
+        IMap.find arity funcList
+    with Not_found -> [] in
+    FuncState(applyMap, IMap.add arity (fct::cList) funcList)
+
+(** AST walking *)
+
+let rec walk_term fs t =
+    match t with
+    | S.Exit ->
+            fs, T.Exit
+    | S.TailCall (func, args) ->
+            let ApplyFunc(applyFct, _), fs =
+                get_apply fs ((List.length args) + 1) in
+            fs, T.TailCall(applyFct, func :: args)
+    | S.Print (v, next) ->
+            let fs, nNext = walk_term fs next in
+            fs, T.Print(v, nNext)
+    | S.LetVal (var, value, next) ->
+            let fs, nNext = walk_term fs next in
+            fs, T.LetVal(var, value, nNext)
+    | S.LetBlo (var, S.Lam(_, vars, body), next) ->
+            (* FIXME is handling of recursive functions correct? *)
+            let fs, nNext = walk_term fs next in
+            let fs, nBody = walk_term fs body in
+            let arity = List.length vars + 1 in
+            let ApplyFunc(_, args), fs =
+                get_apply fs arity in
+            let nBody = List.fold_left2 (fun prevBody formal actual ->
+                T.LetVal(formal, actual, prevBody)) nBody
+                vars
+                (S.vvars (List.tl args)) in
+            let thisTag = freshTag () in
+            let freeVars = Atom.Set.elements @@ S.fv_term body in
+            let thisFunc =
+                T.Branch(thisTag, freeVars, nBody) in
+            let fs = add_func fs arity thisFunc in
+            fs, T.LetBlo (var, T.Con(thisTag, T.vvars freeVars), nNext)
+
+
+let apply_of_arity name args branches =
+    (** Creates a [T.function_declaration] for the [apply] function of the
+     * defunctionalization process, of arity [arity := List.len args]. It thus
+     * handles functions with original arity of [arity - 1], since it also has
+     * to get its closure. *)
+    let body = T.Swi(T.vvar @@ List.hd args, branches) in
+    T.Fun(name, args, body)
+
 let defun_term (t : S.term) : T.program =
-  assert false
+    let FuncState(applyOfArity, funcOfArity), mainTerm =
+        walk_term empty_fs t in
+    let applyFuncs = IMap.fold
+        (fun arity (ApplyFunc(name, args)) accu ->
+            let branches = (try
+                IMap.find arity funcOfArity
+        with Not_found -> raise (InconsistentFuncState arity)) in
+            (apply_of_arity name args branches) :: accu)
+        applyOfArity [] in
+    T.Prog(applyFuncs, mainTerm)