module DerivingDrift.StandardRules (standardRules) where import DerivingDrift.RuleUtils import List import Name.Prim import Name.Name import qualified Data.Map as Map --- Add Rules Below Here ---------------------------------------------------- standardRules :: Map.Map Name.Name.Name (Data -> Doc) standardRules = Map.fromList [ (class_Eq,eqfn), (class_Ord,ordfn), (class_Enum,enumfn), (class_Show,showfn), (class_Read,readfn), (class_Bounded,boundedfn)] ------------------------------------------------------------------------------ -- Rules for the derivable Prelude Classes -- Eq eqfn = instanceSkeleton "Eq" [(makeEq,defaultEq)] makeEq :: IFunction makeEq (Body{constructor=constructor,types=types}) | null types = hsep $ texts [constructor,"==",constructor, "=", "True"] | otherwise = let v = varNames types v' = varNames' types d x = parens . hsep $ text constructor : x head = [ text "==", d v', text "="] body = sepWith (text "&&") $ zipWith (\x y -> (x <+> text "==" <+> y)) v v' in d v <+> fsep (head ++ body) defaultEq = hsep $ texts ["_", "==", "_", "=" ,"False"] ---------------------------------------------------------------------- -- Ord ordfn d = let ifn = [f c c' | c <- zip (body d) [1 :: Int ..] , c' <- zip (body d) [1 :: Int ..]] cmp n n' = show $ compare n n' f (b,n) (b',n') | null (types b) = text "compare" <+> fsep [text (constructor b), pattern (constructor b') (types b') , char '=', text $ cmp n n' ] | otherwise = let head = fsep [l,r, char '='] l = pattern (constructor b) (types b) r = pattern' (constructor b') (types b') one x y = fsep [text "compare",x,y] list [x] [y] = one x y list xs ys = fsep [text "foldl", parens fn, text "EQ", bracketList (zipWith one xs ys)] fn = fsep $ texts ["\\x y", "->", "if", "x", "==","EQ", "then", "compare", "y", "EQ", "else", "x"] in if constructor b == constructor b' then text "compare" <+> fsep [head, list (varNames $ types b) (varNames' $ types b')] else text "compare" <+> fsep [head,text (cmp n n')] in simpleInstance "Ord" d <+> text "where" $$ block ifn ---------------------------------------------------------------------- -- Show & Read -- won't work for infix constructors -- (and anyway, neither does the parser currently) -- -- Show showfn = instanceSkeleton "Show" [(makeShow,empty)] makeShow :: IFunction makeShow (Body{constructor=constructor,labels=labels,types=types}) | null types = fnName <+> fsep [headfn,showString constructor] | null labels = fnName <+> fsep [headfn,bodyStart, body] -- datatype | otherwise = fnName <+> fsep[headfn,bodyStart,recordBody] -- record where fnName = text "showsPrec" headfn = fsep [char 'd',(pattern constructor types),equals] bodyStart = fsep [text "showParen",parens (text "d >= 10")] body = parens . fsep $ sepWith s (c : b) recordBody = parens $ fsep [c,comp,showChar '{',comp, fsep (sepWith s' b'),comp,showChar '}'] c = showString constructor b = map (\x -> fsep[text "showsPrec", text "10", x]) (varNames types) b' = zipWith (\x l -> fsep[showString l,comp,showChar '=',comp,x]) b labels s = fsep [comp,showChar ' ', comp] s' = fsep [comp,showChar ',',comp] showChar c = fsep [text "showChar", text ('\'':c:"\'")] showString s = fsep[ text "showString", doubleQuotes $ text s] comp = char '.' -- Read readfn d = simpleInstance "Read" d <+> text "where" $$ readsPrecFn d readsPrecFn d = let fnName = text "readsPrec" bodies = vcat $ sepWith (text "++") (map makeRead (body d)) in nest 4 $ fnName <+> fsep[char 'd', text "input", equals,bodies] makeRead :: IFunction makeRead (Body{constructor=constructor,labels=labels,types=types}) | null types = fsep [read0,text "input"] | null labels = fsep [headfn,read,text "input"] | otherwise = fsep [headfn,readRecord, text "input"] where headfn = fsep [text "readParen", parens (text "d > 9")] read0 = lambda $ listComp (result rest) [lexConstr rest] read = lambda . listComp (result rest) $ lexConstr ip : ( map f (init vars) ) ++ final (last vars) f v = fsep [tup v ip, from,readsPrec, ip] final v = [fsep[tup v rest,from,readsPrec,ip]] readRecord = let f lab v = [ fsep [tup (text $ show lab) ip,lex], fsep [tup (text $ show "=") ip,lex], fsep [tup v ip ,from,readsPrec,ip]] openB = fsep [tup (text $ show "{") ip,lex] closeB = fsep [tup (text $ show "}") rest,lex] comma = [fsep [tup (text $ show ",") ip,lex]] in lambda . listComp (result rest) $ lexConstr ip : openB : (concat . sepWith comma) (zipWith f labels vars) ++ [closeB] lambda x = parens ( fsep [text "\\",ip,text "->",x]) listComp x ~(l:ll) = brackets . fsep . sepWith comma $ ((fsep[x, char '|', l]) : ll) result x = tup (pattern constructor vars) x lexConstr x = fsep [tup (text $ show constructor) x, lex] -- nifty little bits of syntax vars = varNames types ip = text "inp" rest = text "rest" tup x y = parens $ fsep [x, char ',',y] lex = fsep[from,text "lex",ip] readsPrec = fsep [text "readsPrec",text "10"] from = text "<-" ---------------------------------------------------------------------- -- Enum -- a lot of this code should be provided as default instances, -- but currently isn't enumfn d = let fromE = fromEnumFn d toE = toEnumFn d eFrom = enumFromFn d in if any (not . null . types) (body d) then commentLine $ text "Warning -- can't derive Enum for" <+> text (name d) else simpleInstance "Enum" d <+> text "where" $$ block (fromE ++ toE ++ [eFrom,enumFromThenFn]) fromEnumFn :: Data -> [Doc] fromEnumFn (D{body=body}) = map f (zip body [0:: Int ..]) where f (Body{constructor=constructor},n) = text "fromEnum" <+> (fsep $ texts [constructor , "=", show n]) toEnumFn :: Data -> [Doc] toEnumFn (D{body=body}) = map f (zip body [0 :: Int ..]) where f (Body{constructor=constructor},n) = text "toEnum" <+> (fsep $ texts [show n , "=", constructor]) enumFromFn :: Data -> Doc enumFromFn D{body=body} = let conList = bracketList . texts . map constructor $ body bodydoc = fsep [char 'e', char '=', text "drop", parens (text "fromEnum" <+> char 'e'), conList] in text "enumFrom" <+> bodydoc enumFromThenFn :: Doc enumFromThenFn = let wrapper = fsep $ texts ["i","j","=","enumFromThen\'","i","j","(", "enumFrom", "i", ")"] eq1 = text "enumFromThen\'" <+> fsep (texts ["_","_","[]","=","[]"]) eq2 = text "enumFromThen\'" <+> fsep ( texts ["i","j","(x:xs)","=", "let","d","=","fromEnum","j","-","fromEnum","i","in", "x",":","enumFromThen\'","i","j","(","drop","(d-1)","xs",")"]) in text "enumFromThen" <+> wrapper $$ block [text "where",eq1,eq2] ---------------------------------------------------------------------- -- Bounded - as if anyone uses this one :-) .. boundedfn d@D{name=name,body=body,derives=derives} | all (null . types) body = boundedEnum d | singleton body = boundedSingle d | otherwise = commentLine $ text "Warning -- can't derive Bounded for" <+> text name boundedEnum d@D{body=body} = let f = constructor . head $ body l = constructor . last $ body in simpleInstance "Bounded" d <+> text "where" $$ block [ hsep (texts[ "minBound","=",f]), hsep (texts[ "maxBound","=",l])] boundedSingle d@D{body=body} = let f = head $ body in simpleInstance "Bounded" d <+> text "where" $$ block [ hsep . texts $ [ "minBound","=",constructor f] ++ replicate (length (types f)) "minBound", hsep . texts $ [ "maxBound","=",constructor f] ++ replicate (length (types f)) "maxBound"] singleton [x] = True singleton _ = False