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