From b9633a33182f5b381e912366273709e59f469bb9 Mon Sep 17 00:00:00 2001
From: Mirek Kratochvil <exa.exa@gmail.com>
Date: Sat, 12 Nov 2022 17:47:51 +0100
Subject: reorg.

---
 app/Code.hs | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 app/Code.hs

(limited to 'app/Code.hs')

diff --git a/app/Code.hs b/app/Code.hs
new file mode 100644
index 0000000..3488f0b
--- /dev/null
+++ b/app/Code.hs
@@ -0,0 +1,56 @@
+module Code where
+
+import qualified Data.Map as M
+import IR (Id(..))
+
+data Datum
+  = Atom Int -- unifies a constant
+  | Struct Id -- unifies a structure with arity
+  | VoidRef -- unifies with anything
+  | LocalRef Int -- code-local variable idx (should not occur on heap)
+  | HeapRef Int -- heap structure idx
+  deriving (Show, Eq, Ord)
+
+data Instr
+  = U Datum -- something unifiable
+  | NoGoal -- trivial goal
+  | Goal -- we start a new goal, set up backtracking etc
+  | Call -- all seems okay, call the goal
+  | LastCall -- tail call the goal
+  | Cut -- remove all alternative clauses of the current goal
+  deriving (Show)
+
+type Code = [Instr]
+
+type Defs = M.Map Id [Code]
+
+data Heap =
+  Heap Int (M.Map Int Datum)
+  deriving (Show)
+
+emptyHeap = Heap 0 M.empty
+
+type Scope = M.Map Int Int
+
+emptyScope :: Scope
+emptyScope = M.empty
+
+data Cho =
+  Cho
+    { hed :: Code -- head pointer
+    , hvar :: Scope -- variables unified in head (so far)
+    , gol :: Code -- goal pointer
+    , gvar :: Scope -- variables unified in the goal
+    , heap :: Heap -- a snapshot of the heap (there's no trail; we rely on CoW copies in other choicepoints)
+    , stk :: [(Code, Scope, [Cho])] -- remaining goals together with their vars and cuts
+    , cut :: [Cho] -- snapshot of choicepoints before entering
+    }
+  deriving (Show)
+
+data Interp =
+  Interp
+    { defs :: Defs -- global definitions for lookup (TODO can we externalize?)
+    , cur :: Cho -- the choice that is being evaluated right now
+    , cho :: [Cho] -- remaining choice points
+    }
+  deriving (Show)
-- 
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