%
-% (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}
+#include "HsVersions.h"
+
module DsListComp ( dsListComp ) where
+IMP_Ubiq()
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
+IMPORT_DELOOPER(DsLoop) -- break dsExpr-ish loop
+#else
+import {-# SOURCE #-} DsExpr ( dsExpr )
+import {-# SOURCE #-} DsBinds ( dsBinds )
+#endif
-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 ( Stmt(..), HsExpr, HsBinds )
+import TcHsSyn ( SYN_IE(TypecheckedStmt), SYN_IE(TypecheckedHsExpr) , SYN_IE(TypecheckedHsBinds) )
+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 Id ( SYN_IE(Id) )
+import PrelVals ( mkBuild, foldrId )
+import Type ( mkTyVarTy, mkForAllTy, mkFunTys, mkFunTy, SYN_IE(Type) )
+import TysPrim ( alphaTy )
+import TysWiredIn ( nilDataCon, consDataCon, listTyCon )
+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 :: [TypecheckedStmt]
+ -> Type -- Type of list elements
+ -> DsM CoreExpr
+
+dsListComp quals elt_ty
+ | not opt_FoldrBuildOn -- Be boring
+ = deListComp quals nil_expr
-dsListComp expr quals
- = let expr_ty = typeOfCoreExpr expr
+ | otherwise -- foldr/build lives!
+ = newTyVarsDs [alphaTyVar] `thenDs` \ [n_tyvar] ->
+ let
+ alpha_to_alpha = alphaTy `mkFunTy` alphaTy
+
+ n_ty = mkTyVarTy n_tyvar
+ c_ty = mkFunTys [elt_ty, n_ty] n_ty
+ g_ty = mkForAllTy alphaTyVar (
+ (elt_ty `mkFunTy` alpha_to_alpha)
+ `mkFunTy`
+ alpha_to_alpha
+ )
in
- ifSwitchSetDs FoldrBuildOn (
- 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))
- in
- newSysLocalsDs [c_ty,n_ty,g_ty] `thenDs` \ [c, n, g] ->
-
- dfListComp expr expr_ty
- 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] []
+ newSysLocalsDs [c_ty,n_ty,g_ty] `thenDs` \ [c, n, g] ->
- new_alpha_tyvar :: DsM (TyVar, UniType)
- new_alpha_tyvar
- = newTyVarsDs [alpha_tv] `thenDs` \ [new_ty] ->
- returnDs (new_ty,mkTyVarTy new_ty)
+ dfListComp c_ty c
+ n_ty n
+ quals `thenDs` \ result ->
+
+ returnDs (mkBuild elt_ty n_tyvar c n g result)
+ where
+ nil_expr = mkCon nilDataCon [] [elt_ty] []
\end{code}
%************************************************************************
already desugared. @dsListComp@ does the top TE rule mentioned above.
\begin{code}
-deListComp :: PlainCoreExpr -> [TypecheckedQual] -> PlainCoreExpr -> DsM PlainCoreExpr
+deListComp :: [TypecheckedStmt] -> CoreExpr -> DsM CoreExpr
-deListComp expr [] list -- Figure 7.4, SLPJ, p 135, rule C above
- = mkCoConDs consDataCon [typeOfCoreExpr expr] [expr, list]
+deListComp [ReturnStmt expr] list -- Figure 7.4, SLPJ, p 135, rule C above
+ = dsExpr expr `thenDs` \ core_expr ->
+ mkConDs consDataCon [TyArg (coreExprType core_expr), VarArg core_expr, VarArg list]
-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 (GuardStmt guard locn : quals) list -- rule B above
+ = dsExpr guard `thenDs` \ core_guard ->
+ deListComp quals list `thenDs` \ core_rest ->
+ returnDs (mkCoreIfThenElse core_guard core_rest list)
-deListComp expr ((GeneratorQual pat list1):quals) core_list2 -- rule A' above
+-- [e | let B, qs] = let B in [e | qs]
+deListComp (LetStmt binds : quals) list
+ = dsBinds False{-don't auto scc-} binds `thenDs` \ core_binds ->
+ deListComp quals list `thenDs` \ core_rest ->
+ returnDs (mkCoLetsAny core_binds core_rest)
+
+deListComp (BindStmt pat list1 locn : 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
- in
- newSysLocalsDs [h_ty, u1_ty, u2_ty, u3_ty]
- `thenDs` \ [h', u1, u2, u3] ->
- {-
- Make the function h unfoldable by the deforester.
- 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)
- else h'
- in
- -- the "fail" value ...
- mkCoAppDs (CoVar h) (CoVar u3) `thenDs` \ core_fail ->
+ u2_ty = outPatType pat
- deListComp expr quals core_fail `thenDs` \ rest_expr ->
-
- matchSimply (CoVar u2) pat res_ty rest_expr core_fail `thenDs` \ core_match ->
+ res_ty = coreExprType core_list2
+ h_ty = u1_ty `mkFunTy` res_ty
+ in
+ newSysLocalsDs [h_ty, u1_ty, u2_ty, u3_ty] `thenDs` \ [h, u1, u2, u3] ->
- mkCoAppDs (CoVar h) core_list1 `thenDs` \ letrec_body ->
+ -- the "fail" value ...
+ mkAppDs (Var h) [VarArg (Var u3)] `thenDs` \ core_fail ->
+ deListComp quals core_fail `thenDs` \ rest_expr ->
+ matchSimply (Var u2) pat res_ty
+ rest_expr core_fail `thenDs` \ core_match ->
+ mkAppDs (Var h) [VarArg core_list1] `thenDs` \ letrec_body ->
returnDs (
mkCoLetrecAny [
( h,
- (CoLam [ u1 ]
- (CoCase (CoVar u1)
- (CoAlgAlts
- [(nilDataCon, [], core_list2),
- (consDataCon, [u2, u3], core_match)]
- CoNoDefault)))
+ (Lam (ValBinder u1)
+ (Case (Var u1)
+ (AlgAlts
+ [(nilDataCon, [], core_list2),
+ (consDataCon, [u2, u3], core_match)]
+ 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
- -> [TypecheckedQual] -- the rest of the qual's
- -> DsM PlainCoreExpr
-
-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 ((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))
-
-dfListComp expr expr_ty c_ty c_id n_ty n_id ((GeneratorQual pat list1):quals)
+dfListComp :: Type -> Id -- 'c'; its type and id
+ -> Type -> Id -- 'n'; its type and id
+ -> [TypecheckedStmt] -- the rest of the qual's
+ -> DsM CoreExpr
+
+dfListComp c_ty c_id n_ty n_id [ReturnStmt expr]
+ = dsExpr expr `thenDs` \ core_expr ->
+ mkAppDs (Var c_id) [VarArg core_expr, VarArg (Var n_id)]
+
+dfListComp c_ty c_id n_ty n_id (GuardStmt guard locn : quals)
+ = dsExpr guard `thenDs` \ core_guard ->
+ dfListComp c_ty c_id n_ty n_id quals `thenDs` \ core_rest ->
+ returnDs (mkCoreIfThenElse core_guard core_rest (Var n_id))
+
+dfListComp c_ty c_id n_ty n_id (LetStmt binds : quals)
+ -- new in 1.3, local bindings
+ = dsBinds False{-don't auto scc-} binds `thenDs` \ core_binds ->
+ dfListComp c_ty c_id n_ty n_id quals `thenDs` \ core_rest ->
+ returnDs (mkCoLetsAny core_binds core_rest)
+
+dfListComp c_ty c_id n_ty n_id (BindStmt pat list1 locn : 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
-- build rest of the comprehesion
- dfListComp expr expr_ty c_ty c_id b_ty b quals `thenDs` \ core_rest ->
+ dfListComp 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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