%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
%
\section[DsListComp]{Desugaring list comprehensions}
\begin{code}
module DsListComp ( dsListComp ) where
+import Ubiq
+import DsLoop -- break dsExpr-ish loop
-import AbsSyn -- the stuff being desugared
-import PlainCore -- the output of desugaring;
- -- importing this module also gets all the
- -- CoreSyn utility functions
-import DsMonad -- the monadery used in the desugarer
+import HsSyn ( Qual(..), HsExpr, HsBinds )
+import TcHsSyn ( TypecheckedQual(..), TypecheckedHsExpr(..) )
+import DsHsSyn ( outPatType )
+import CoreSyn
-import AbsPrel ( mkFunTy, nilDataCon, consDataCon, listTyCon,
- mkBuild, mkFoldr
- )
-import AbsUniType ( alpha_tv, alpha, mkTyVarTy, mkForallTy )
-import CmdLineOpts ( GlobalSwitch(..) )
-import DsExpr ( dsExpr )
+import DsMonad -- the monadery used in the desugarer
import DsUtils
-import Id ( getIdInfo, replaceIdInfo )
-import IdInfo
+
+import CmdLineOpts ( opt_FoldrBuildOn )
+import CoreUtils ( coreExprType, mkCoreIfThenElse )
+import PrelInfo ( nilDataCon, consDataCon, listTyCon,
+ mkBuild, foldrId )
+import Type ( mkTyVarTy, mkForAllTy, mkFunTys )
+import TysPrim ( alphaTy )
+import TyVar ( alphaTyVar )
import Match ( matchSimply )
-import Util
+import Util ( panic )
\end{code}
List comprehensions may be desugared in one of two ways: ``ordinary''
There will be at least one ``qualifier'' in the input.
\begin{code}
-dsListComp :: PlainCoreExpr -> [TypecheckedQual] -> DsM PlainCoreExpr
+dsListComp :: CoreExpr -> [TypecheckedQual] -> DsM CoreExpr
dsListComp expr quals
- = let expr_ty = typeOfCoreExpr expr
+ = let
+ expr_ty = coreExprType expr
in
- ifSwitchSetDs FoldrBuildOn (
+ if not opt_FoldrBuildOn then -- be boring
+ deListComp expr quals (nIL_EXPR expr_ty)
+
+ else -- foldr/build lives!
new_alpha_tyvar `thenDs` \ (n_tyvar, n_ty) ->
let
- c_ty = expr_ty `mkFunTy` (n_ty `mkFunTy` n_ty)
- g_ty = mkForallTy [alpha_tv] (
- (expr_ty `mkFunTy` (alpha `mkFunTy` alpha))
- `mkFunTy` (alpha `mkFunTy` alpha))
+ alpha_to_alpha = mkFunTys [alphaTy] alphaTy
+
+ c_ty = mkFunTys [expr_ty, n_ty] n_ty
+ g_ty = mkForAllTy alphaTyVar (
+ (mkFunTys [expr_ty, alpha_to_alpha] alpha_to_alpha))
in
- newSysLocalsDs [c_ty,n_ty,g_ty] `thenDs` \ [c, n, g] ->
+ newSysLocalsDs [c_ty,n_ty,g_ty] `thenDs` \ [c, n, g] ->
dfListComp expr expr_ty
- c_ty c
+ c_ty c
n_ty n
quals `thenDs` \ result ->
returnDs (mkBuild expr_ty n_tyvar c n g result)
-
- ) {-else be boring-} (
- deListComp expr quals (nIL_EXPR expr_ty)
- )
where
- nIL_EXPR ty = CoCon nilDataCon [ty] []
+ nIL_EXPR ty = mkCon nilDataCon [] [ty] []
- new_alpha_tyvar :: DsM (TyVar, UniType)
+ new_alpha_tyvar :: DsM (TyVar, Type)
new_alpha_tyvar
- = newTyVarsDs [alpha_tv] `thenDs` \ [new_ty] ->
+ = newTyVarsDs [alphaTyVar] `thenDs` \ [new_ty] ->
returnDs (new_ty,mkTyVarTy new_ty)
\end{code}
already desugared. @dsListComp@ does the top TE rule mentioned above.
\begin{code}
-deListComp :: PlainCoreExpr -> [TypecheckedQual] -> PlainCoreExpr -> DsM PlainCoreExpr
+deListComp :: CoreExpr -> [TypecheckedQual] -> CoreExpr -> DsM CoreExpr
deListComp expr [] list -- Figure 7.4, SLPJ, p 135, rule C above
- = mkCoConDs consDataCon [typeOfCoreExpr expr] [expr, list]
+ = mkConDs consDataCon [coreExprType expr] [expr, list]
-deListComp expr ((FilterQual filt): quals) list -- rule B above
+deListComp expr (FilterQual filt : quals) list -- rule B above
= dsExpr filt `thenDs` \ core_filt ->
deListComp expr quals list `thenDs` \ core_rest ->
returnDs ( mkCoreIfThenElse core_filt core_rest list )
+deListComp expr (LetQual binds : quals) list
+ = panic "deListComp:LetQual"
+
deListComp expr ((GeneratorQual pat list1):quals) core_list2 -- rule A' above
= dsExpr list1 `thenDs` \ core_list1 ->
let
- u3_ty@u1_ty = typeOfCoreExpr core_list1 -- two names, same thing
+ u3_ty@u1_ty = coreExprType core_list1 -- two names, same thing
-- u1_ty is a [alpha] type, and u2_ty = alpha
- u2_ty = typeOfPat pat
-
- res_ty = typeOfCoreExpr core_list2
- h_ty = mkFunTy u1_ty res_ty
+ u2_ty = outPatType pat
+
+ res_ty = coreExprType core_list2
+ h_ty = mkFunTys [u1_ty] res_ty
in
newSysLocalsDs [h_ty, u1_ty, u2_ty, u3_ty]
`thenDs` \ [h', u1, u2, u3] ->
Since it only occurs once in the body, we can't get
an increase in code size by unfolding it.
-}
--- getSwitchCheckerDs `thenDs` \ sw_chkr ->
let
h = if False -- LATER: sw_chkr DoDeforest???
- then replaceIdInfo h' (addInfo (getIdInfo h') DoDeforest)
+ then panic "deListComp:deforest"
+ -- replaceIdInfo h' (addInfo (getIdInfo h') DoDeforest)
else h'
in
-- the "fail" value ...
- mkCoAppDs (CoVar h) (CoVar u3) `thenDs` \ core_fail ->
+ mkAppDs (Var h) [] [Var u3] `thenDs` \ core_fail ->
deListComp expr quals core_fail `thenDs` \ rest_expr ->
- matchSimply (CoVar u2) pat res_ty rest_expr core_fail `thenDs` \ core_match ->
+ matchSimply (Var u2) pat res_ty rest_expr core_fail `thenDs` \ core_match ->
- mkCoAppDs (CoVar h) core_list1 `thenDs` \ letrec_body ->
+ mkAppDs (Var h) [] [core_list1] `thenDs` \ letrec_body ->
returnDs (
mkCoLetrecAny [
( h,
- (CoLam [ u1 ]
- (CoCase (CoVar u1)
- (CoAlgAlts
+ (Lam (ValBinder u1)
+ (Case (Var u1)
+ (AlgAlts
[(nilDataCon, [], core_list2),
(consDataCon, [u2, u3], core_match)]
- CoNoDefault)))
+ NoDefault)))
)] letrec_body
)
\end{code}
\begin{verbatim}
TE < [ e | ] >> c n = c e n
TE << [ e | b , q ] >> c n = if b then TE << [ e | q ] >> c n else n
-TE << [ e | p <- l , q ] c n = foldr
- (\ TE << p >> b -> TE << [ e | q ] >> c b
+TE << [ e | p <- l , q ] c n = foldr
+ (\ TE << p >> b -> TE << [ e | q ] >> c b
_ b -> b) n l
\end{verbatim}
\begin{code}
-dfListComp :: PlainCoreExpr -- the inside of the comp
- -> UniType -- the type of the inside
- -> UniType -> Id -- 'c'; its type and id
- -> UniType -> Id -- 'n'; its type and id
+dfListComp :: CoreExpr -- the inside of the comp
+ -> Type -- the type of the inside
+ -> Type -> Id -- 'c'; its type and id
+ -> Type -> Id -- 'n'; its type and id
-> [TypecheckedQual] -- the rest of the qual's
- -> DsM PlainCoreExpr
+ -> DsM CoreExpr
-dfListComp expr expr_ty c_ty c_id n_ty n_id []
- = mkCoAppDs (CoVar c_id) expr `thenDs` \ inner ->
- mkCoAppDs inner (CoVar n_id)
+dfListComp expr expr_ty c_ty c_id n_ty n_id []
+ = mkAppDs (Var c_id) [] [expr, Var n_id]
-dfListComp expr expr_ty c_ty c_id n_ty n_id ((FilterQual filt) : quals)
+dfListComp expr expr_ty c_ty c_id n_ty n_id (FilterQual filt : quals)
= dsExpr filt `thenDs` \ core_filt ->
dfListComp expr expr_ty c_ty c_id n_ty n_id quals
`thenDs` \ core_rest ->
- returnDs (mkCoreIfThenElse core_filt core_rest (CoVar n_id))
+ returnDs (mkCoreIfThenElse core_filt core_rest (Var n_id))
-dfListComp expr expr_ty c_ty c_id n_ty n_id ((GeneratorQual pat list1):quals)
+dfListComp expr expr_ty c_ty c_id n_ty n_id (LetQual binds : quals)
+ = panic "dfListComp:LetQual"
+
+dfListComp expr expr_ty c_ty c_id n_ty n_id (GeneratorQual pat list1 : quals)
-- evaluate the two lists
= dsExpr list1 `thenDs` \ core_list1 ->
-- find the required type
- let p_ty = typeOfPat pat
- b_ty = n_ty -- alias b_ty to n_ty
- fn_ty = p_ty `mkFunTy` (b_ty `mkFunTy` b_ty)
- lst_ty = typeOfCoreExpr core_list1
+ let p_ty = outPatType pat
+ b_ty = n_ty -- alias b_ty to n_ty
+ fn_ty = mkFunTys [p_ty, b_ty] b_ty
+ lst_ty = coreExprType core_list1
in
-- create some new local id's
dfListComp expr expr_ty c_ty c_id b_ty b quals `thenDs` \ core_rest ->
-- build the pattern match
- matchSimply (CoVar p) pat b_ty core_rest (CoVar b) `thenDs` \ core_expr ->
+ matchSimply (Var p) pat b_ty core_rest (Var b) `thenDs` \ core_expr ->
-- now build the outermost foldr, and return
returnDs (
mkCoLetsAny
- [CoNonRec fn (CoLam [p,b] core_expr),
- CoNonRec lst core_list1]
+ [NonRec fn (mkValLam [p, b] core_expr),
+ NonRec lst core_list1]
(mkFoldr p_ty n_ty fn n_id lst)
)
-\end{code}
+mkFoldr a b f z xs
+ = mkValApp (mkTyApp (Var foldrId) [a,b]) [VarArg f, VarArg z, VarArg xs]
+\end{code}
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