\section[PatSyntax]{Abstract Haskell syntax---patterns}
\begin{code}
-#include "HsVersions.h"
-
module HsPat (
InPat(..),
OutPat(..),
collectPatBinders
) where
-IMP_Ubiq()
+#include "HsVersions.h"
-- friends:
--- IMPORT_DELOOPER(IdLoop)
import HsBasic ( HsLit )
import HsExpr ( HsExpr )
import BasicTypes ( Fixity )
-- others:
-import Id ( SYN_IE(Id), dataConTyCon, GenId )
+import Id ( Id, dataConTyCon, GenId )
import Maybes ( maybeToBool )
-import Outputable ( PprStyle(..), userStyle, interppSP,
- interpp'SP, ifPprShowAll, Outputable(..)
- )
-import Pretty
+import Outputable
import TyCon ( maybeTyConSingleCon )
import PprType ( GenType )
-import CmdLineOpts ( opt_PprUserLength )
-#if __GLASGOW_HASKELL__ >= 202
-import Name
-#endif
+import Name ( NamedThing )
\end{code}
Patterns come in distinct before- and after-typechecking flavo(u)rs.
| RecPatIn name -- record
[(name, InPat name, Bool)] -- True <=> source used punning
-data OutPat tyvar uvar id
- = WildPat (GenType tyvar uvar) -- wild card
+data OutPat flexi id
+ = WildPat (GenType flexi) -- wild card
| VarPat id -- variable (type is in the Id)
- | LazyPat (OutPat tyvar uvar id) -- lazy pattern
+ | LazyPat (OutPat flexi id) -- lazy pattern
| AsPat id -- as pattern
- (OutPat tyvar uvar id)
+ (OutPat flexi id)
| ConPat Id -- Constructor is always an Id
- (GenType tyvar uvar) -- the type of the pattern
- [OutPat tyvar uvar id]
+ (GenType flexi) -- the type of the pattern
+ [OutPat flexi id]
- | ConOpPat (OutPat tyvar uvar id) -- just a special case...
+ | ConOpPat (OutPat flexi id) -- just a special case...
Id
- (OutPat tyvar uvar id)
- (GenType tyvar uvar)
+ (OutPat flexi id)
+ (GenType flexi)
| ListPat -- syntactic list
- (GenType tyvar uvar) -- the type of the elements
- [OutPat tyvar uvar id]
+ (GenType flexi) -- the type of the elements
+ [OutPat flexi id]
- | TuplePat [OutPat tyvar uvar id] -- tuple
+ | TuplePat [OutPat flexi 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
+ (GenType flexi) -- the type of the pattern
+ [(Id, OutPat flexi 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
+ (GenType flexi) -- 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))
+ (GenType flexi) -- type of pattern, t
+ (HsExpr flexi id (OutPat flexi id))
-- of type t -> Bool; detects match
| NPlusKPat id
-- (This could be an Integer, but then
-- it's harder to partitionEqnsByLit
-- in the desugarer.)
- (GenType tyvar uvar) -- Type of pattern, t
- (HsExpr tyvar uvar id (OutPat tyvar uvar id)) -- Of type t -> Bool; detects match
- (HsExpr tyvar uvar id (OutPat tyvar uvar id)) -- Of type t -> t; subtracts k
+ (GenType flexi) -- Type of pattern, t
+ (HsExpr flexi id (OutPat flexi id)) -- Of type t -> Bool; detects match
+ (HsExpr flexi id (OutPat flexi id)) -- Of type t -> t; subtracts k
| DictPat -- Used when destructing Dictionaries with an explicit case
[id] -- superclass dicts
instance (Outputable name) => Outputable (InPat name) where
ppr = pprInPat
-pprInPat :: (Outputable name) => PprStyle -> InPat name -> Doc
+pprInPat :: (Outputable name) => InPat name -> SDoc
-pprInPat sty (WildPatIn) = char '_'
-pprInPat sty (VarPatIn var) = ppr sty var
-pprInPat sty (LitPatIn s) = ppr sty s
-pprInPat sty (LazyPatIn pat) = (<>) (char '~') (ppr sty pat)
-pprInPat sty (AsPatIn name pat)
- = parens (hcat [ppr sty name, char '@', ppr sty pat])
+pprInPat (WildPatIn) = char '_'
+pprInPat (VarPatIn var) = ppr var
+pprInPat (LitPatIn s) = ppr s
+pprInPat (LazyPatIn pat) = char '~' <> ppr pat
+pprInPat (AsPatIn name pat) = parens (hcat [ppr name, char '@', ppr pat])
-pprInPat sty (ConPatIn c pats)
- = if null pats then
- ppr sty c
- else
- hsep [ppr sty c, interppSP sty pats] -- ParPats put in the parens
+pprInPat (ConPatIn c pats)
+ | null pats = ppr c
+ | otherwise = hsep [ppr c, interppSP pats] -- ParPats put in the parens
-pprInPat sty (ConOpPatIn pat1 op fixity pat2)
- = hsep [ppr sty pat1, ppr sty op, ppr sty pat2] -- ParPats put in parens
+pprInPat (ConOpPatIn pat1 op fixity pat2)
+ = hsep [ppr pat1, ppr op, 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)
-pprInPat sty (NegPatIn pat)
+pprInPat (NegPatIn pat)
= let
- pp_pat = pprInPat sty pat
+ pp_pat = pprInPat pat
in
- (<>) (char '-') (
+ char '-' <> (
case pat of
LitPatIn _ -> pp_pat
_ -> parens pp_pat
)
-pprInPat sty (ParPatIn pat)
- = parens (pprInPat sty pat)
+pprInPat (ParPatIn pat)
+ = parens (pprInPat pat)
-pprInPat sty (ListPatIn pats)
- = brackets (interpp'SP sty pats)
-pprInPat sty (TuplePatIn pats)
- = parens (interpp'SP sty pats)
-pprInPat sty (NPlusKPatIn n k)
- = parens (hcat [ppr sty n, char '+', ppr sty k])
+pprInPat (ListPatIn pats)
+ = brackets (interpp'SP pats)
+pprInPat (TuplePatIn pats)
+ = parens (interpp'SP pats)
+pprInPat (NPlusKPatIn n k)
+ = parens (hcat [ppr n, char '+', ppr k])
-pprInPat sty (RecPatIn con rpats)
- = hsep [ppr sty con, braces (hsep (punctuate comma (map (pp_rpat sty) rpats)))]
+pprInPat (RecPatIn con rpats)
+ = hsep [ppr con, braces (hsep (punctuate comma (map (pp_rpat) rpats)))]
where
- pp_rpat sty (v, _, True) | userStyle sty = ppr (PprForUser opt_PprUserLength) v
- pp_rpat sty (v, p, _) = hsep [ppr sty v, char '=', ppr sty p]
+ pp_rpat (v, _, True) = ppr v
+ pp_rpat (v, p, _) = hsep [ppr v, char '=', ppr p]
\end{code}
\begin{code}
-instance (Eq tyvar, Outputable tyvar, Eq uvar, Outputable uvar, Outputable id)
- => Outputable (OutPat tyvar uvar id) where
+instance (Outputable id) => Outputable (OutPat flexi id) where
ppr = pprOutPat
\end{code}
\begin{code}
-pprOutPat sty (WildPat ty) = char '_'
-pprOutPat sty (VarPat var) = ppr sty var
-pprOutPat sty (LazyPat pat) = hcat [char '~', ppr sty pat]
-pprOutPat sty (AsPat name pat)
- = parens (hcat [ppr sty name, char '@', ppr sty pat])
-
-pprOutPat sty (ConPat name ty [])
- = (<>) (ppr sty name)
- (ifPprShowAll sty (pprConPatTy sty ty))
-
-pprOutPat sty (ConPat name ty pats)
- = hcat [parens (hcat [ppr sty name, space, interppSP sty pats]),
- ifPprShowAll sty (pprConPatTy sty ty) ]
-
-pprOutPat sty (ConOpPat pat1 op pat2 ty)
- = parens (hcat [ppr sty pat1, space, ppr sty op, space, ppr sty pat2])
-
-pprOutPat sty (ListPat ty pats)
- = brackets (interpp'SP sty pats)
-pprOutPat sty (TuplePat pats)
- = parens (interpp'SP sty pats)
-
-pprOutPat sty (RecPat con ty rpats)
- = hcat [ppr sty con, braces (hsep (punctuate comma (map (pp_rpat sty) rpats)))]
+pprOutPat (WildPat ty) = char '_'
+pprOutPat (VarPat var) = ppr var
+pprOutPat (LazyPat pat) = hcat [char '~', ppr pat]
+pprOutPat (AsPat name pat)
+ = parens (hcat [ppr name, char '@', ppr pat])
+
+pprOutPat (ConPat name ty [])
+ = ppr name
+
+pprOutPat (ConPat name ty pats)
+ = hcat [parens (hcat [ppr name, space, interppSP pats])]
+
+pprOutPat (ConOpPat pat1 op pat2 ty)
+ = parens (hcat [ppr pat1, space, ppr op, space, ppr pat2])
+
+pprOutPat (ListPat ty pats)
+ = brackets (interpp'SP pats)
+pprOutPat (TuplePat pats)
+ = parens (interpp'SP pats)
+
+pprOutPat (RecPat con ty rpats)
+ = hcat [ppr con, braces (hsep (punctuate comma (map (pp_rpat) rpats)))]
where
- pp_rpat sty (v, _, True) | userStyle sty = ppr (PprForUser opt_PprUserLength) v
- pp_rpat sty (v, p, _) = hsep [ppr sty v, char '=', ppr sty p]
+ pp_rpat (v, _, True) = ppr v
+ pp_rpat (v, p, _) = hsep [ppr v, char '=', ppr p]
-pprOutPat sty (LitPat l ty) = ppr sty l -- ToDo: print more
-pprOutPat sty (NPat l ty e) = ppr sty l -- ToDo: print more
-pprOutPat sty (NPlusKPat n k ty e1 e2) -- ToDo: print more
- = parens (hcat [ppr sty n, char '+', ppr sty k])
+pprOutPat (LitPat l ty) = ppr l -- ToDo: print more
+pprOutPat (NPat l ty e) = ppr l -- ToDo: print more
+pprOutPat (NPlusKPat n k ty e1 e2) -- ToDo: print more
+ = parens (hcat [ppr n, char '+', ppr k])
-pprOutPat sty (DictPat dicts methods)
+pprOutPat (DictPat dicts methods)
= parens (sep [ptext SLIT("{-dict-}"),
- brackets (interpp'SP sty dicts),
- brackets (interpp'SP sty methods)])
+ brackets (interpp'SP dicts),
+ brackets (interpp'SP methods)])
-pprConPatTy sty ty
- = parens (ppr sty ty)
+pprConPatTy ty
+ = parens (ppr ty)
\end{code}
%************************************************************************
The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are.
\begin{code}
-irrefutablePats :: [OutPat a b c] -> Bool
+irrefutablePats :: [OutPat a b] -> Bool
irrefutablePats pat_list = all irrefutablePat pat_list
irrefutablePat (AsPat _ pat) = irrefutablePat pat
irrefutablePat (DictPat ds ms) = (length ds + length ms) <= 1
irrefutablePat other = False
-failureFreePat :: OutPat a b c -> Bool
+failureFreePat :: OutPat a b -> Bool
failureFreePat (WildPat _) = True
failureFreePat (VarPat _) = True
\end{code}
\begin{code}
-patsAreAllCons :: [OutPat a b c] -> Bool
+patsAreAllCons :: [OutPat a b] -> Bool
patsAreAllCons pat_list = all isConPat pat_list
isConPat (AsPat _ pat) = isConPat pat
isConPat (DictPat ds ms) = (length ds + length ms) > 1
isConPat other = False
-patsAreAllLits :: [OutPat a b c] -> Bool
+patsAreAllLits :: [OutPat a b] -> Bool
patsAreAllLits pat_list = all isLitPat pat_list
isLitPat (AsPat _ pat) = isLitPat pat
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