%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[PatSyntax]{Abstract Haskell syntax---patterns}
\begin{code}
-#include "HsVersions.h"
-
module HsPat (
- InPat(..),
- OutPat(..),
+ Pat(..), InPat, OutPat,
+
+ HsConDetails(..), hsConArgs,
- unfailablePats, unfailablePat,
- patsAreAllCons, isConPat,
+ mkPrefixConPat, mkCharLitPat, mkNilPat,
+
+ isWildPat,
+ patsAreAllCons, isConPat, isSigPat,
patsAreAllLits, isLitPat,
- irrefutablePat,
- collectPatBinders
+ collectPatBinders, collectPatsBinders,
+ collectSigTysFromPat, collectSigTysFromPats
) where
-import Ubiq
+#include "HsVersions.h"
+
--- friends:
-import HsLit ( HsLit )
-import HsLoop ( HsExpr )
+import {-# SOURCE #-} HsExpr ( HsExpr )
+-- friends:
+import HsLit ( HsLit(HsCharPrim), HsOverLit )
+import HsTypes ( HsType, SyntaxName, PostTcType )
+import BasicTypes ( Boxity, tupleParens )
-- others:
-import Id ( GenId, dataConSig )
-import Maybes ( maybeToBool )
-import Name ( pprOp, pprNonOp )
-import Outputable ( interppSP, interpp'SP, ifPprShowAll )
-import PprStyle ( PprStyle(..) )
-import Pretty
-import TyCon ( maybeTyConSingleCon )
-import PprType ( GenType )
+import TysWiredIn ( nilDataCon, charDataCon, charTy )
+import Var ( TyVar )
+import DataCon ( DataCon )
+import Outputable
+import Type ( Type )
\end{code}
-Patterns come in distinct before- and after-typechecking flavo(u)rs.
+
\begin{code}
-data InPat name
- = WildPatIn -- wild card
- | VarPatIn name -- variable
- | LitPatIn HsLit -- literal
- | LazyPatIn (InPat name) -- lazy pattern
- | AsPatIn name -- as pattern
- (InPat name)
- | ConPatIn name -- constructed type
- [InPat name]
- | ConOpPatIn (InPat name)
- name
- (InPat name)
-
- -- We preserve prefix negation and parenthesis for the precedence parser.
-
- | NegPatIn (InPat name) -- negated pattern
- | ParPatIn (InPat name) -- parenthesised pattern
-
- | ListPatIn [InPat name] -- syntactic list
- -- must have >= 1 elements
- | TuplePatIn [InPat name] -- tuple
-
- | RecPatIn name -- record
- [(name, InPat name, Bool)] -- True <=> source used punning
-
-data OutPat tyvar uvar id
- = WildPat (GenType tyvar uvar) -- wild card
-
- | VarPat id -- variable (type is in the Id)
-
- | LazyPat (OutPat tyvar uvar id) -- lazy pattern
-
- | AsPat id -- as pattern
- (OutPat tyvar uvar id)
-
- | ConPat Id -- Constructor is always an Id
- (GenType tyvar uvar) -- the type of the pattern
- [(OutPat tyvar uvar id)]
-
- | ConOpPat (OutPat tyvar uvar id) -- just a special case...
- Id
- (OutPat tyvar uvar id)
- (GenType tyvar uvar)
- | ListPat -- syntactic list
- (GenType tyvar uvar) -- the type of the elements
- [(OutPat tyvar uvar id)]
-
- | TuplePat [(OutPat tyvar uvar id)] -- tuple
- -- UnitPat is TuplePat []
-
- | RecPat Id -- record constructor
- (GenType tyvar uvar) -- the type of the pattern
- [(id, OutPat tyvar uvar id, Bool)] -- True <=> source used punning
-
- | LitPat -- Used for *non-overloaded* literal patterns:
- -- Int#, Char#, Int, Char, String, etc.
- HsLit
- (GenType tyvar uvar) -- type of pattern
-
- | NPat -- Used for *overloaded* literal patterns
- HsLit -- the literal is retained so that
- -- the desugarer can readily identify
- -- equations with identical literal-patterns
- (GenType tyvar uvar) -- type of pattern, t
- (HsExpr tyvar uvar id (OutPat tyvar uvar id))
- -- of type t -> Bool; detects match
-
- | DictPat -- Used when destructing Dictionaries with an explicit case
+type InPat id = Pat id -- No 'Out' constructors
+type OutPat id = Pat id -- No 'In' constructors
+
+data Pat id
+ = ------------ Simple patterns ---------------
+ WildPat PostTcType -- Wild card
+ | VarPat id -- Variable
+ | LazyPat (Pat id) -- Lazy pattern
+ | AsPat id (Pat id) -- As pattern
+ | ParPat (Pat id) -- Parenthesised pattern
+
+ ------------ Lists, tuples, arrays ---------------
+ | ListPat [Pat id] -- Syntactic list
+ PostTcType -- The type of the elements
+
+ | TuplePat [Pat id] -- Tuple
+ Boxity -- UnitPat is TuplePat []
+
+ | PArrPat [Pat id] -- Syntactic parallel array
+ PostTcType -- The type of the elements
+
+ ------------ Constructor patterns ---------------
+ | ConPatIn id
+ (HsConDetails id (Pat id))
+
+ | ConPatOut DataCon
+ (HsConDetails id (Pat id))
+ Type -- The type of the pattern
+ [TyVar] -- Existentially bound type variables
+ [id] -- Ditto dictionaries
+
+ ------------ Literal and n+k patterns ---------------
+ | LitPat HsLit -- Used for *non-overloaded* literal patterns:
+ -- Int#, Char#, Int, Char, String, etc.
+
+ | NPatIn HsOverLit -- Always positive
+ (Maybe SyntaxName) -- Just (Name of 'negate') for negative
+ -- patterns, Nothing otherwise
+
+ | NPatOut HsLit -- Used for literal patterns where there's an equality function to call
+ -- The literal is retained so that the desugarer can readily identify
+ -- equations with identical literal-patterns
+ -- Always HsInteger, HsRat or HsString.
+ -- Always HsInteger, HsRat or HsString.
+ -- *Unlike* NPatIn, for negative literals, the
+ -- literal is acutally negative!
+ Type -- Type of pattern, t
+ (HsExpr id) -- Of type t -> Bool; detects match
+
+ | NPlusKPatIn id -- n+k pattern
+ HsOverLit -- It'll always be an HsIntegral
+ SyntaxName -- Name of '-' (see RnEnv.lookupSyntaxName)
+
+ | NPlusKPatOut id
+ Integer
+ (HsExpr id) -- Of type t -> Bool; detects match
+ (HsExpr id) -- Of type t -> t; subtracts k
+
+
+ ------------ Generics ---------------
+ | TypePat (HsType id) -- Type pattern for generic definitions
+ -- e.g f{| a+b |} = ...
+ -- These show up only in class declarations,
+ -- and should be a top-level pattern
+
+ ------------ Pattern type signatures ---------------
+ | SigPatIn (Pat id) -- Pattern with a type signature
+ (HsType id)
+
+ | SigPatOut (Pat id) -- Pattern p
+ Type -- Type, t, of the whole pattern
+ (HsExpr id) -- Coercion function,
+ -- of type t -> typeof(p)
+
+ ------------ Dictionary patterns (translation only) ---------------
+ | DictPat -- Used when destructing Dictionaries with an explicit case
[id] -- superclass dicts
[id] -- methods
\end{code}
+HsConDetails is use both for patterns and for data type declarations
+
+\begin{code}
+data HsConDetails id arg
+ = PrefixCon [arg] -- C p1 p2 p3
+ | RecCon [(id, arg)] -- C { x = p1, y = p2 }
+ | InfixCon arg arg -- p1 `C` p2
+
+hsConArgs :: HsConDetails id arg -> [arg]
+hsConArgs (PrefixCon ps) = ps
+hsConArgs (RecCon fs) = map snd fs
+hsConArgs (InfixCon p1 p2) = [p1,p2]
+\end{code}
+
+
+%************************************************************************
+%* *
+%* Printing patterns
+%* *
+%************************************************************************
+
\begin{code}
-instance (Outputable name, NamedThing name) => Outputable (InPat name) where
- ppr = pprInPat
+instance (OutputableBndr name) => Outputable (Pat name) where
+ ppr = pprPat
-pprInPat :: (Outputable name, NamedThing name) => PprStyle -> InPat name -> Pretty
+pprPat :: (OutputableBndr name) => Pat name -> SDoc
-pprInPat sty (WildPatIn) = ppStr "_"
-pprInPat sty (VarPatIn var) = pprNonOp sty var
-pprInPat sty (LitPatIn s) = ppr sty s
-pprInPat sty (LazyPatIn pat) = ppBeside (ppChar '~') (ppr sty pat)
-pprInPat sty (AsPatIn name pat)
- = ppBesides [ppLparen, ppr sty name, ppChar '@', ppr sty pat, ppRparen]
+pprPat (VarPat var) -- Print with type info if -dppr-debug is on
+ = getPprStyle $ \ sty ->
+ if debugStyle sty then
+ parens (pprBndr LambdaBind var) -- Could pass the site to pprPat
+ -- but is it worth it?
+ else
+ ppr var
-pprInPat sty (ConPatIn c pats)
- = if null pats then
- ppr sty c
- else
- ppBesides [ppLparen, ppr sty c, ppSP, interppSP sty pats, ppRparen]
+pprPat (WildPat _) = char '_'
+pprPat (LazyPat pat) = char '~' <> ppr pat
+pprPat (AsPat name pat) = parens (hcat [ppr name, char '@', ppr pat])
+pprPat (ParPat pat) = parens (pprPat pat)
+pprPat (ListPat pats _) = brackets (interpp'SP pats)
+pprPat (PArrPat pats _) = pabrackets (interpp'SP pats)
+pprPat (TuplePat pats bx) = tupleParens bx (interpp'SP pats)
-pprInPat sty (ConOpPatIn pat1 op pat2)
- = ppBesides [ppLparen, ppr sty pat1, ppSP, ppr sty op, ppSP, ppr sty pat2, ppRparen]
+pprPat (ConPatIn c details) = pprConPat c details
+pprPat (ConPatOut c details _ _ _) = pprConPat c details
+
+pprPat (LitPat s) = ppr s
+pprPat (NPatIn l _) = ppr l
+pprPat (NPatOut l _ _) = ppr l
+pprPat (NPlusKPatIn n k _) = hcat [ppr n, char '+', ppr k]
+pprPat (NPlusKPatOut n k _ _) = hcat [ppr n, char '+', integer k]
+
+pprPat (TypePat ty) = ptext SLIT("{|") <> ppr ty <> ptext SLIT("|}")
+
+pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty
+pprPat (SigPatOut pat ty _) = ppr pat <+> dcolon <+> ppr ty
+
+pprPat (DictPat dicts methods)
+ = parens (sep [ptext SLIT("{-dict-}"),
+ brackets (interpp'SP dicts),
+ brackets (interpp'SP methods)])
- -- ToDo: use pprOp to print op (but this involves fiddling various
- -- contexts & I'm lazy...); *PatIns are *rarely* printed anyway... (WDP)
-pprInPat sty (NegPatIn pat)
- = let
- pp_pat = pprInPat sty pat
- in
- ppBeside (ppChar '-') (
- case pat of
- LitPatIn _ -> pp_pat
- _ -> ppParens pp_pat
- )
-
-pprInPat sty (ParPatIn pat)
- = ppParens (pprInPat sty pat)
-
-pprInPat sty (ListPatIn pats)
- = ppBesides [ppLbrack, interpp'SP sty pats, ppRbrack]
-pprInPat sty (TuplePatIn pats)
- = ppBesides [ppLparen, interpp'SP sty pats, ppRparen]
-
-pprInPat sty (RecPatIn con rpats)
- = ppBesides [ppr sty con, ppSP, ppChar '{', ppInterleave ppComma (map pp_rpat rpats), ppChar '}']
+
+pprConPat con (PrefixCon pats) = ppr con <+> interppSP pats -- inner ParPats supply the necessary parens.
+pprConPat con (InfixCon pat1 pat2) = hsep [ppr pat1, ppr con, ppr pat2] -- ParPats put in parens
+ -- ToDo: use pprSym to print op (but this involves fiddling various
+ -- contexts & I'm lazy...); *PatIns are *rarely* printed anyway... (WDP)
+pprConPat con (RecCon rpats)
+ = ppr con <+> braces (hsep (punctuate comma (map (pp_rpat) rpats)))
where
- pp_rpat (v, _, True{-pun-}) = ppr sty v
- pp_rpat (v, p, _) = ppCat [ppr sty v, ppStr "<-", ppr sty p]
-\end{code}
+ pp_rpat (v, p) = hsep [ppr v, char '=', ppr p]
-\begin{code}
-instance (Eq tyvar, Outputable tyvar, Eq uvar, Outputable uvar,
- NamedThing id, Outputable id)
- => Outputable (OutPat tyvar uvar id) where
- ppr = pprOutPat
+
+-- add parallel array brackets around a document
+--
+pabrackets :: SDoc -> SDoc
+pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
\end{code}
-\begin{code}
-pprOutPat sty (WildPat ty) = ppChar '_'
-pprOutPat sty (VarPat var) = pprNonOp sty var
-pprOutPat sty (LazyPat pat) = ppBesides [ppChar '~', ppr sty pat]
-pprOutPat sty (AsPat name pat)
- = ppBesides [ppLparen, ppr sty name, ppChar '@', ppr sty pat, ppRparen]
-
-pprOutPat sty (ConPat name ty [])
- = ppBeside (ppr sty name)
- (ifPprShowAll sty (pprConPatTy sty ty))
-
-pprOutPat sty (ConPat name ty pats)
- = ppBesides [ppLparen, ppr sty name, ppSP,
- interppSP sty pats, ppRparen,
- ifPprShowAll sty (pprConPatTy sty ty) ]
-
-pprOutPat sty (ConOpPat pat1 op pat2 ty)
- = ppBesides [ppLparen, ppr sty pat1, ppSP, pprOp sty op, ppSP, ppr sty pat2, ppRparen]
-
-pprOutPat sty (ListPat ty pats)
- = ppBesides [ppLbrack, interpp'SP sty pats, ppRbrack]
-pprOutPat sty (TuplePat pats)
- = ppBesides [ppLparen, interpp'SP sty pats, ppRparen]
-
-pprOutPat sty (RecPat con ty rpats)
- = ppBesides [ppr sty con, ppChar '{', ppInterleave ppComma (map pp_rpat rpats), ppChar '}']
- where
--- pp_rpat (v, _, True{-pun-}) = ppr sty v
- pp_rpat (v, p, _) = ppBesides [ppr sty v, ppStr "<-", ppr sty p]
-pprOutPat sty (LitPat l ty) = ppr sty l -- ToDo: print more
-pprOutPat sty (NPat l ty e) = ppr sty l -- ToDo: print more
+%************************************************************************
+%* *
+%* Building patterns
+%* *
+%************************************************************************
-pprOutPat sty (DictPat dicts methods)
- = ppSep [ppBesides [ppLparen, ppPStr SLIT("{-dict-}")],
- ppBracket (interpp'SP sty dicts),
- ppBesides [ppBracket (interpp'SP sty methods), ppRparen]]
+\begin{code}
+mkPrefixConPat :: DataCon -> [OutPat id] -> Type -> OutPat id
+-- Make a vanilla Prefix constructor pattern
+mkPrefixConPat dc pats ty = ConPatOut dc (PrefixCon pats) ty [] []
+
+mkNilPat :: Type -> OutPat id
+mkNilPat ty = mkPrefixConPat nilDataCon [] ty
-pprConPatTy sty ty
- = ppParens (ppr sty ty)
+mkCharLitPat :: Int -> OutPat id
+mkCharLitPat c = mkPrefixConPat charDataCon [LitPat (HsCharPrim c)] charTy
\end{code}
+
%************************************************************************
%* *
-%* predicates for checking things about pattern-lists in EquationInfo *
+%* Predicates for checking things about pattern-lists in EquationInfo *
%* *
%************************************************************************
+
\subsection[Pat-list-predicates]{Look for interesting things in patterns}
Unlike in the Wadler chapter, where patterns are either ``variables''
A pattern is in {\em exactly one} of the above three categories; `as'
patterns are treated specially, of course.
+The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are.
\begin{code}
-unfailablePats :: [OutPat a b c] -> Bool
-unfailablePats pat_list = all unfailablePat pat_list
+isWildPat (WildPat _) = True
+isWildPat other = False
-unfailablePat (AsPat _ pat) = unfailablePat pat
-unfailablePat (WildPat _) = True
-unfailablePat (VarPat _) = True
-unfailablePat (LazyPat _) = True
-unfailablePat (DictPat ds ms) = (length ds + length ms) <= 1
-unfailablePat other = False
-
-patsAreAllCons :: [OutPat a b c] -> Bool
+patsAreAllCons :: [Pat id] -> Bool
patsAreAllCons pat_list = all isConPat pat_list
isConPat (AsPat _ pat) = isConPat pat
-isConPat (ConPat _ _ _) = True
-isConPat (ConOpPat _ _ _ _) = True
+isConPat (ConPatIn _ _) = True
+isConPat (ConPatOut _ _ _ _ _) = True
isConPat (ListPat _ _) = True
-isConPat (TuplePat _) = True
+isConPat (PArrPat _ _) = True
+isConPat (TuplePat _ _) = True
isConPat (DictPat ds ms) = (length ds + length ms) > 1
isConPat other = False
-patsAreAllLits :: [OutPat a b c] -> Bool
+isSigPat (SigPatIn _ _) = True
+isSigPat (SigPatOut _ _ _) = True
+isSigPat other = False
+
+patsAreAllLits :: [Pat id] -> Bool
patsAreAllLits pat_list = all isLitPat pat_list
-isLitPat (AsPat _ pat) = isLitPat pat
-isLitPat (LitPat _ _) = True
-isLitPat (NPat _ _ _) = True
-isLitPat other = False
+isLitPat (AsPat _ pat) = isLitPat pat
+isLitPat (LitPat _) = True
+isLitPat (NPatIn _ _) = True
+isLitPat (NPatOut _ _ _) = True
+isLitPat (NPlusKPatIn _ _ _) = True
+isLitPat (NPlusKPatOut _ _ _ _) = True
+isLitPat other = False
\end{code}
-A pattern is irrefutable if a match on it cannot fail
-(at any depth).
-\begin{code}
-irrefutablePat :: OutPat a b c -> Bool
-
-irrefutablePat (WildPat _) = True
-irrefutablePat (VarPat _) = True
-irrefutablePat (LazyPat _) = True
-irrefutablePat (AsPat _ pat) = irrefutablePat pat
-irrefutablePat (ConPat con tys pats) = all irrefutablePat pats && only_con con
-irrefutablePat (ConOpPat pat1 con pat2 _) = irrefutablePat pat1 && irrefutablePat pat1 && only_con con
-irrefutablePat (ListPat _ _) = False
-irrefutablePat (TuplePat pats) = all irrefutablePat pats
-irrefutablePat (DictPat _ _) = True
-irrefutablePat other_pat = False -- Literals, NPat
-
-only_con con = maybeToBool (maybeTyConSingleCon tycon)
- where
- (_,_,_,tycon) = dataConSig con
-\end{code}
+%************************************************************************
+%* *
+%* Gathering stuff out of patterns
+%* *
+%************************************************************************
This function @collectPatBinders@ works with the ``collectBinders''
functions for @HsBinds@, etc. The order in which the binders are
collected is important; see @HsBinds.lhs@.
+
+It collects the bounds *value* variables in renamed patterns; type variables
+are *not* collected.
+
+\begin{code}
+collectPatBinders :: Pat a -> [a]
+collectPatBinders pat = collect pat []
+
+collectPatsBinders :: [Pat a] -> [a]
+collectPatsBinders pats = foldr collect [] pats
+
+collect (WildPat _) bndrs = bndrs
+collect (VarPat var) bndrs = var : bndrs
+collect (LazyPat pat) bndrs = collect pat bndrs
+collect (AsPat a pat) bndrs = a : collect pat bndrs
+collect (ParPat pat) bndrs = collect pat bndrs
+
+collect (ListPat pats _) bndrs = foldr collect bndrs pats
+collect (PArrPat pats _) bndrs = foldr collect bndrs pats
+collect (TuplePat pats _) bndrs = foldr collect bndrs pats
+
+collect (ConPatIn c ps) bndrs = foldr collect bndrs (hsConArgs ps)
+collect (ConPatOut c ps _ _ ds) bndrs = ds ++ foldr collect bndrs (hsConArgs ps)
+
+collect (LitPat _) bndrs = bndrs
+collect (NPatIn _ _) bndrs = bndrs
+collect (NPatOut _ _ _) bndrs = bndrs
+
+collect (NPlusKPatIn n _ _) bndrs = n : bndrs
+collect (NPlusKPatOut n _ _ _) bndrs = n : bndrs
+
+collect (SigPatIn pat _) bndrs = collect pat bndrs
+collect (SigPatOut pat _ _) bndrs = collect pat bndrs
+collect (TypePat ty) bndrs = bndrs
+collect (DictPat ids1 ids2) bndrs = ids1 ++ ids2 ++ bndrs
+\end{code}
+
\begin{code}
-collectPatBinders :: InPat a -> [a]
-
-collectPatBinders (VarPatIn var) = [var]
-collectPatBinders (LazyPatIn pat) = collectPatBinders pat
-collectPatBinders (AsPatIn a pat) = a : collectPatBinders pat
-collectPatBinders (ConPatIn c pats) = concat (map collectPatBinders pats)
-collectPatBinders (ConOpPatIn p1 c p2)= collectPatBinders p1 ++ collectPatBinders p2
-collectPatBinders (NegPatIn pat) = collectPatBinders pat
-collectPatBinders (ParPatIn pat) = collectPatBinders pat
-collectPatBinders (ListPatIn pats) = concat (map collectPatBinders pats)
-collectPatBinders (TuplePatIn pats) = concat (map collectPatBinders pats)
-collectPatBinders any_other_pat = [ {-no binders-} ]
+collectSigTysFromPats :: [InPat name] -> [HsType name]
+collectSigTysFromPats pats = foldr collect_pat [] pats
+
+collectSigTysFromPat :: InPat name -> [HsType name]
+collectSigTysFromPat pat = collect_pat pat []
+
+collect_pat (SigPatIn pat ty) acc = collect_pat pat (ty:acc)
+collect_pat (TypePat ty) acc = ty:acc
+
+collect_pat (LazyPat pat) acc = collect_pat pat acc
+collect_pat (AsPat a pat) acc = collect_pat pat acc
+collect_pat (ParPat pat) acc = collect_pat pat acc
+collect_pat (ListPat pats _) acc = foldr collect_pat acc pats
+collect_pat (PArrPat pats _) acc = foldr collect_pat acc pats
+collect_pat (TuplePat pats _) acc = foldr collect_pat acc pats
+collect_pat (ConPatIn c ps) acc = foldr collect_pat acc (hsConArgs ps)
+collect_pat other acc = acc -- Literals, vars, wildcard
\end{code}
+
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