292 lines
11 KiB
Idris
292 lines
11 KiB
Idris
module Lib.Eval
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-- For FC
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import Lib.Parser.Impl
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import Lib.Prettier
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import Lib.Types
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import Lib.TopContext
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import Control.Monad.Error.Interface
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import Data.IORef
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import Data.Fin
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import Data.List
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import Data.SnocList
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import Data.Vect
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import Data.SortedMap
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-- Need to wire in the metas...
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-- if it's top / ctx / IORef, I also need IO...
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-- if I want errors, I need m anyway. I've already got an error down there.
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export
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eval : Env -> Mode -> Tm -> M Val
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-- REVIEW everything is evalutated whether it's needed or not
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-- It would be nice if the environment were lazy.
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-- e.g. case is getting evaluated when passed to a function because
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-- of dependencies in pi-types, even if the dependency isn't used
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public export
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($$) : {auto mode : Mode} -> Closure -> Val -> M Val
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($$) {mode} (MkClosure env tm) u = eval (u :: env) mode tm
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public export
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infixl 8 $$
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export
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vapp : Val -> Val -> M Val
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vapp (VLam _ _ _ _ t) u = t $$ u
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vapp (VVar fc k sp) u = pure $ VVar fc k (sp :< u)
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vapp (VRef fc nm def sp) u = pure $ VRef fc nm def (sp :< u)
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vapp (VMeta fc k sp) u = pure $ VMeta fc k (sp :< u)
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vapp t u = error' "impossible in vapp \{show t} to \{show u}\n"
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export
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vappSpine : Val -> SnocList Val -> M Val
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vappSpine t [<] = pure t
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vappSpine t (xs :< x) = vapp !(vappSpine t xs) x
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lookupVar : Env -> Nat -> Maybe Val
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lookupVar env k = let l = length env in
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if k > l
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then Nothing
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else case getAt ((l `minus` k) `minus` 1) env of
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Just v@(VVar fc k' sp) => if k == k' then Nothing else Just v
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Just v => Just v
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Nothing => Nothing
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-- hoping to apply what we got via pattern matching
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export
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unlet : Env -> Val -> M Val
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unlet env t@(VVar fc k sp) = case lookupVar env k of
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Just tt@(VVar fc' k' sp') => do
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debug "lookup \{show k} is \{show tt}"
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if k' == k then pure t else (vappSpine (VVar fc' k' sp') sp >>= unlet env)
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Just t => vappSpine t sp >>= unlet env
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Nothing => do
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debug "lookup \{show k} is Nothing in env \{show env}"
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pure t
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unlet env x = pure x
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export
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tryEval : Env -> Val -> M (Maybe Val)
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tryEval env (VRef fc k _ sp) =
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case lookup k !(get) of
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Just (MkEntry name ty (Fn tm)) =>
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catchError {e=Error} (
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do
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debug "app \{name} to \{show sp}"
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vtm <- eval [] CBN tm
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debug "tm is \{pprint [] tm}"
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case !(vappSpine vtm sp) of
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VCase{} => pure Nothing
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v => pure $ Just v)
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(\ _ => pure Nothing)
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_ => pure Nothing
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tryEval _ _ = pure Nothing
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-- Force far enough to compare types
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export
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forceType : Env -> Val -> M Val
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forceType env (VMeta fc ix sp) = case !(lookupMeta ix) of
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(Unsolved x k xs _ _ _) => pure (VMeta fc ix sp)
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(Solved _ k t) => vappSpine t sp >>= forceType env
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forceType env x = do
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Just x' <- tryEval env x
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| _ => pure x
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forceType env x'
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evalCase : Env -> Mode -> Val -> List CaseAlt -> M (Maybe Val)
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evalCase env mode sc@(VRef _ nm _ sp) (cc@(CaseCons name nms t) :: xs) =
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if nm == name
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then do
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debug "ECase \{nm} \{show sp} \{show nms} \{showTm t}"
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go env (sp <>> []) nms
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else case lookup nm !(get) of
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(Just (MkEntry str type (DCon k str1))) => evalCase env mode sc xs
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-- bail for a stuck function
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_ => pure Nothing
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where
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go : Env -> List Val -> List String -> M (Maybe Val)
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go env (arg :: args) (nm :: nms) = go (arg :: env) args nms
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go env args [] = Just <$> vappSpine !(eval env mode t) ([<] <>< args)
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go env [] rest = pure Nothing
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-- REVIEW - this is handled in the caller already
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evalCase env mode sc@(VVar fc k sp) alts = case lookupVar env k of
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Just tt@(VVar fc' k' sp') => do
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debug "lookup \{show k} is \{show tt}"
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if k' == k then pure Nothing
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else evalCase env mode !(vappSpine (VVar fc' k' sp') sp) alts
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Just t => evalCase env mode !(vappSpine t sp) alts
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Nothing => do
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debug "lookup \{show k} is Nothing in env \{show env}"
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pure Nothing
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evalCase env mode sc (CaseDefault u :: xs) = pure $ Just !(eval (sc :: env) mode u)
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evalCase env mode sc cc = do
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debug "CASE BAIL sc \{show sc} vs \{show cc}"
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debug "env is \{show env}"
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pure Nothing
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bind : Val -> Env -> Env
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bind v env = v :: env
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-- So smalltt says:
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-- Smalltt has the following approach:
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-- - Top-level and local definitions are lazy.
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-- - We instantiate Pi types during elaboration with lazy values.
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-- - Applications headed by top-level variables are lazy.
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-- - Any other function application is call-by-value during evaluation.
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-- TODO maybe add glueing
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eval env mode (Ref fc x def) = pure $ VRef fc x def [<]
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eval env mode (App _ t u) = vapp !(eval env mode t) !(eval env mode u)
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eval env mode (U fc) = pure (VU fc)
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eval env mode (Erased fc) = pure (VErased fc)
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eval env mode (Meta fc i) =
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case !(lookupMeta i) of
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(Unsolved _ k xs _ _ _) => pure $ VMeta fc i [<]
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(Solved _ k t) => pure $ t
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eval env mode (Lam fc x icit rig t) = pure $ VLam fc x icit rig (MkClosure env t)
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eval env mode (Pi fc x icit rig a b) = pure $ VPi fc x icit rig !(eval env mode a) (MkClosure env b)
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eval env mode (Let fc nm t u) = pure $ VLet fc nm !(eval env mode t) !(eval (VVar fc (length env) [<] :: env) mode u)
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eval env mode (LetRec fc nm ty t u) = pure $ VLetRec fc nm !(eval env mode ty) !(eval (VVar fc (length env) [<] :: env) mode t) !(eval (VVar fc (length env) [<] :: env) mode u)
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-- Here, we assume env has everything. We push levels onto it during type checking.
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-- I think we could pass in an l and assume everything outside env is free and
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-- translate to a level
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eval env mode (Bnd fc i) = case getAt i env of
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Just rval => pure rval
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Nothing => error fc "Bad deBruin index \{show i}"
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eval env mode (Lit fc lit) = pure $ VLit fc lit
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eval env mode tm@(Case fc sc alts) = do
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-- TODO we need to be able to tell eval to expand aggressively here.
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sc' <- eval env mode sc
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sc' <- unlet env sc' -- try to expand lets from pattern matching
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sc' <- forceType env sc'
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pure $ fromMaybe (VCase fc !(eval env mode sc) alts)
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!(evalCase env mode sc' alts)
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export
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quote : (lvl : Nat) -> Val -> M Tm
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quoteSp : (lvl : Nat) -> Tm -> SnocList Val -> M Tm
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quoteSp lvl t [<] = pure t
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quoteSp lvl t (xs :< x) =
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pure $ App emptyFC !(quoteSp lvl t xs) !(quote lvl x)
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quote l (VVar fc k sp) = if k < l
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then quoteSp l (Bnd fc ((l `minus` k) `minus` 1)) sp -- level to index
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else ?borken
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quote l (VMeta fc i sp) =
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case !(lookupMeta i) of
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(Unsolved _ k xs _ _ _) => quoteSp l (Meta fc i) sp
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(Solved _ k t) => quote l !(vappSpine t sp)
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quote l (VLam fc x icit rig t) = pure $ Lam fc x icit rig !(quote (S l) !(t $$ VVar emptyFC l [<]))
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quote l (VPi fc x icit rig a b) = pure $ Pi fc x icit rig !(quote l a) !(quote (S l) !(b $$ VVar emptyFC l [<]))
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quote l (VLet fc nm t u) = pure $ Let fc nm !(quote l t) !(quote (S l) u)
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quote l (VLetRec fc nm ty t u) = pure $ LetRec fc nm !(quote l ty) !(quote (S l) t) !(quote (S l) u)
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quote l (VU fc) = pure (U fc)
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quote l (VRef fc n def sp) = quoteSp l (Ref fc n def) sp
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quote l (VCase fc sc alts) = pure $ Case fc !(quote l sc) alts
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quote l (VLit fc lit) = pure $ Lit fc lit
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quote l (VErased fc) = pure $ Erased fc
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-- Can we assume closed terms?
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-- ezoo only seems to use it at [], but essentially does this:
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export
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nf : Env -> Tm -> M Tm
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nf env t = quote (length env) !(eval env CBN t)
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export
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nfv : Env -> Tm -> M Tm
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nfv env t = quote (length env) !(eval env CBV t)
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export
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prvalCtx : {auto ctx : Context} -> Val -> M String
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prvalCtx v = pure $ interpolate $ pprint (toList $ map fst ctx.types) !(quote ctx.lvl v)
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-- REVIEW - might be easier if we inserted the meta without a bunch of explicit App
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-- I believe Kovacs is doing that.
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-- we need to walk the whole thing
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-- meta in Tm have a bunch of args, which should be the relevant
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-- parts of the scope. So, meta has a bunch of lambdas, we've got a bunch of
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-- args and we need to beta reduce, which seems like a lot of work for nothing
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-- Could we put the "good bits" of the Meta in there and write it to Bnd directly
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-- off of scope? I guess this might get dicey when a meta is another meta applied
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-- to something.
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-- ok, so we're doing something that looks lot like eval, having to collect args,
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-- pull the def, and apply spine. Eval is trying for WHNF, so it doesn't walk the
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-- whole thing. (We'd like to insert metas inside lambdas.)
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export
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zonk : TopContext -> Nat -> Env -> Tm -> M Tm
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zonkBind : TopContext -> Nat -> Env -> Tm -> M Tm
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zonkBind top l env tm = zonk top (S l) (VVar (getFC tm) l [<] :: env) tm
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-- I don't know if app needs an FC...
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appSpine : Tm -> List Tm -> Tm
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appSpine t [] = t
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appSpine t (x :: xs) = appSpine (App (getFC t) t x) xs
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-- REVIEW When metas are subst in, the fc point elsewhere
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-- We might want to update when it is solved and update recursively?
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-- For errors, I think we want to pretend the code has been typed in place
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tweakFC : FC -> Tm -> Tm
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tweakFC fc (Bnd fc1 k) = Bnd fc k
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tweakFC fc (Ref fc1 nm x) = Ref fc nm x
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tweakFC fc (U fc1) = U fc
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tweakFC fc (Meta fc1 k) = Meta fc k
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tweakFC fc (Lam fc1 nm icit rig t) = Lam fc nm icit rig t
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tweakFC fc (App fc1 t u) = App fc t u
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tweakFC fc (Pi fc1 nm icit x t u) = Pi fc nm icit x t u
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tweakFC fc (Case fc1 t xs) = Case fc t xs
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tweakFC fc (Let fc1 nm t u) = Let fc nm t u
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tweakFC fc (LetRec fc1 nm ty t u) = LetRec fc nm ty t u
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tweakFC fc (Lit fc1 lit) = Lit fc lit
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tweakFC fc (Erased fc1) = Erased fc
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-- TODO replace this with a variant on nf
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zonkApp : TopContext -> Nat -> Env -> Tm -> List Tm -> M Tm
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zonkApp top l env (App fc t u) sp = zonkApp top l env t (!(zonk top l env u) :: sp)
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zonkApp top l env t@(Meta fc k) sp = case !(lookupMeta k) of
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(Solved _ j v) => do
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sp' <- traverse (eval env CBN) sp
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debug "zonk \{show k} -> \{show v} spine \{show sp'}"
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foo <- vappSpine v ([<] <>< sp')
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debug "-> result is \{show foo}"
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tweakFC fc <$> quote l foo
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(Unsolved x j xs _ _ _) => pure $ appSpine t sp
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zonkApp top l env t sp = pure $ appSpine !(zonk top l env t) sp
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zonkAlt : TopContext -> Nat -> Env -> CaseAlt -> M CaseAlt
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zonkAlt top l env (CaseDefault t) = CaseDefault <$> zonkBind top l env t
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zonkAlt top l env (CaseLit lit t) = CaseLit lit <$> zonkBind top l env t
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zonkAlt top l env (CaseCons name args t) = CaseCons name args <$> go l env args t
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where
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go : Nat -> Env -> List String -> Tm -> M Tm
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go l env [] tm = zonk top l env t
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go l env (x :: xs) tm = go (S l) (VVar (getFC tm) l [<] :: env) xs tm
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zonk top l env t = case t of
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(Meta fc k) => zonkApp top l env t []
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(Lam fc nm icit rig u) => Lam fc nm icit rig <$> (zonk top (S l) (VVar fc l [<] :: env) u)
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(App fc t u) => zonkApp top l env t [!(zonk top l env u)]
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(Pi fc nm icit rig a b) => Pi fc nm icit rig <$> zonk top l env a <*> zonkBind top l env b
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(Let fc nm t u) => Let fc nm <$> zonk top l env t <*> zonkBind top l env u
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(LetRec fc nm ty t u) => LetRec fc nm <$> zonk top l env ty <*> zonkBind top l env t <*> zonkBind top l env u
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(Case fc sc alts) => Case fc <$> zonk top l env sc <*> traverse (zonkAlt top l env) alts
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U fc => pure $ U fc
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Lit fc lit => pure $ Lit fc lit
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Bnd fc ix => pure $ Bnd fc ix
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Ref fc ix def => pure $ Ref fc ix def
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Erased fc => pure $ Erased fc
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