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|
{-|
Derives @Read@. This is as defined by the Haskell report, except
there is no support for infix constructors. If you attempt to
derive @Read@ for a data type with infix constructors, the
constructors are handled as if they were prefix constructors, using
the @(@/consym/@)@ syntax.
-}
module Data.Derive.Read(makeRead) where
{-
import Prelude
example :: Custom
instance Read a => Read (Sample a) where
readsPrec p0 r =
readParen $(bracket 0) (\r0 -> $(comp 0 First )) r ++
readParen $(bracket 1) (\r0 -> $(comp 1 Second)) r ++
readParen $(bracket 2) (\r0 -> $(comp 2 Third )) r ++
[]
test :: Sample
instance Read a => Read (Sample a) where
readsPrec p0 r =
readParen (p0 > 10) (\r0 ->
[ (First, r1)
| ("First", r1) <- lex r0]) r
++
readParen (p0 > 10) (\r0 ->
[ (Second x1 x2, r3)
| ("Second", r1) <- lex r0
, (x1, r2) <- readsPrec 11 r1
, (x2, r3) <- readsPrec 11 r2]) r
++
readParen (p0 > 10) (\r0 ->
[ (Third x1, r2)
| ("Third", r1) <- lex r0
, (x1, r2) <- readsPrec 11 r1]) r
test :: Computer
instance Read Computer where
readsPrec _ r =
readParen False (\r0 ->
[ (Laptop x1 x2, r10)
| ("Laptop", r1) <- lex r0
, ("{", r2) <- lex r1
, ("weight", r3) <- lex r2
, ("=", r4) <- lex r3
, (x1, r5) <- readsPrec 0 r4
, (",", r6) <- lex r5
, ("speed", r7) <- lex r6
, ("=", r8) <- lex r7
, (x2, r9) <- readsPrec 0 r8
, ("}", r10) <- lex r9]) r
++
readParen False (\r0 ->
[ (Desktop x1, r6)
| ("Desktop", r1) <- lex r0
, ("{", r2) <- lex r1
, ("speed", r3) <- lex r2
, ("=", r4) <- lex r3
, (x1, r5) <- readsPrec 0 r4
, ("}", r6) <- lex r5]) r
test :: (:*:)
instance (Read a, Read b) => Read ((:*:) a b) where
readsPrec p0 r =
readParen (p0 > 10) (\r0 ->
[ ((:*:) x1 x2, r3)
| ("(:*:)", r1) <- lex r0
, (x1, r2) <- readsPrec 11 r1
, (x2, r3) <- readsPrec 11 r2]) r
-}
import Data.Derive.DSL.HSE
import qualified Language.Haskell as H
-- GENERATED START
import Data.Derive.DSL.DSL
import Data.Derive.Internal.Derivation
makeRead :: Derivation
makeRead = derivationCustomDSL "Read" custom $
List [Instance ["Read"] "Read" (List [App "InsDecl" (List [App
"FunBind" (List [List [App "Match" (List [App "Ident" (List [
String "readsPrec"]),List [App "PVar" (List [App "Ident" (List [
Concat (List [String "p",ShowInt (Int 0)])])]),App "PVar" (List [
App "Ident" (List [String "r"])])],App "Nothing" (List []),App
"UnGuardedRhs" (List [Fold (App "InfixApp" (List [Head,App
"QVarOp" (List [App "UnQual" (List [App "Symbol" (List [String
"++"])])]),Tail])) (Concat (List [MapCtor (Application (List [App
"Var" (List [App "UnQual" (List [App "Ident" (List [String
"readParen"])])]),App "SpliceExp" (List [App "ParenSplice" (List [
App "App" (List [App "Var" (List [App "UnQual" (List [App "Ident"
(List [String "bracket"])])]),App "Lit" (List [App "Int" (List [
CtorIndex])])])])]),App "Paren" (List [App "Lambda" (List [List [
App "PVar" (List [App "Ident" (List [Concat (List [String "r",
ShowInt (Int 0)])])])],App "SpliceExp" (List [App "ParenSplice" (
List [Application (List [App "Var" (List [App "UnQual" (List [App
"Ident" (List [String "comp"])])]),App "Lit" (List [App "Int" (
List [CtorIndex])]),App "Con" (List [App "UnQual" (List [App
"Ident" (List [CtorName])])])])])])])]),App "Var" (List [App
"UnQual" (List [App "Ident" (List [String "r"])])])])),List [App
"List" (List [List []])]]))]),App "BDecls" (List [List []])])]])])
])]
-- GENERATED STOP
custom = customSplice splice
getCtor d i = dataDeclCtors (snd d) !! fromIntegral i
hasFields c = any ((/=) "" . fst) $ ctorDeclFields c
splice :: FullDataDecl -> Exp -> Exp
splice d (H.App x (H.Lit (H.Int y))) | x ~= "bracket" =
if hasFields $ getCtor d y
then con "False"
else Paren $ InfixApp (var "p0") (QVarOp $ UnQual $ Symbol ">") (H.Lit $ H.Int 10)
splice d (H.App (H.App x (H.Lit (H.Int y))) _) | x ~= "comp" =
if hasFields c then readFields c else readCtor c
where c = getCtor d y
readCtor :: CtorDecl -> Exp
readCtor c =
ListComp (Tuple Boxed [cpat, var ('r':show (cn+1))]) $
matchStr (ctorDeclName c) 0 :
[QualStmt $ Generator sl
(PTuple Boxed [pVar $ v 'x' 0, pVar $ v 'r' 1])
(apps (var "readsPrec") [H.Lit $ H.Int 11, var $ v 'r' 0])
| i <- [1..cn], let v c j = c : show (i+j)]
where
cn = ctorDeclArity c
cpat = apps (Con $ UnQual $ ctorDeclName' c) $ map (var . ('x':) . show) [1..cn]
readFields :: CtorDecl -> Exp
readFields c =
ListComp (Tuple Boxed [cpat, var $ 'r':show ((cn*4)+2)]) $
matchStr (ctorDeclName c) 0 :
concat [
matchStr (r == 1 ? "{" $ ",") r :
matchStr fld (r+1) :
matchStr "=" (r+2) :
QualStmt (Generator sl
(PTuple Boxed [pVar $ 'x':show i, pVar $ 'r':show (r+4)])
(apps (var "readsPrec") [H.Lit $ H.Int 0, var $ 'r':show (r+3)]))
: []
| (i,r,(fld,_)) <- zip3 [1..] [1,5..] (ctorDeclFields c)
] ++
[matchStr "}" ((cn*4)+1)]
where
cn = ctorDeclArity c
cpat = apps (Con $ UnQual $ ctorDeclName' c) $ map (var . ('x':) . show) [1..cn]
matchStr :: String -> Int -> QualStmt
matchStr s i = QualStmt $ Generator sl (PTuple Boxed [PLit $ H.String s, pVar $ 'r':show (i+1)]) (var "lex" `H.App` var ('r':show i))
{-
read' dat = [instance_default "Read" dat [funN "readsPrec" [sclause [vr "p0", vr "r"] body]]]
where
body = (++::) [ readit ctr | ctr <- dataCtors dat ]
readit ctr = case ctorFields ctr of [] -> norm
fl -> flds fl
where
norm = lK "readParen"
[vr "p0" >: lit (10::Integer),
"r0" ->: runComp (pName . foldr (.) id (map (pRead 11) (ctv ctr 'x'))) (ctp ctr 'x'),
l0 "r"]
flds f = lK "readParen"
[false,
"r0" ->: runComp (pName . pLex "{" .
foldr (.) id (intersperse (pLex ",")
(zipWith pField (ctv ctr 'x') f)) .
pLex "}") (ctp ctr 'x'),
l0 "r"]
runComp fn ex = CompE $ fn (\k -> [ NoBindS (tup [ex, vrn 'r' k]) ]) 0
pArse pat fun ct k = BindS (tup [pat, vrn 'r' (k+1)]) (AppE fun (vrn 'r' k)) : ct (k+1)
pLex pat = pArse (lit pat) (l0 "lex")
name = ctorName ctr
pName | isAlpha (head name) || head name == '_' = pLex name
| otherwise = pLex "(" . pLex name . pLex ")"
pRead pc pat = pArse pat (l1 "readsPrec" (lit (pc :: Integer)))
pField pat fld = pLex fld . pLex "=" . pRead 0 pat
-}
|
