HIMA' #6 発表資料。 Parser と Pretty Printer を統合するこころみであるところの invertible-syntax の説明と、その基盤である partial-isomorphisms の解説です。 Template Haskell もあるよ！

1. invertible-syntax
(TH )
Hiromi Ishii
a.k.a. @mr_konn

2. About myself...
• id:mr_konn / @mr_konn
• Template Haskell
• P Haskell

3. TOC
• invertible-syntax
• JSON Parser Pretty Printer
• Inside invertible-syntax
• Real World Template Haskell

4. TOC
• invertible-syntax
• JSON Parser Pretty Printer
• Inside invertible-syntax
• Real World Template Haskell

5. invertible-syntax

6. Haskeller

7. Haskeller
•

8. Haskeller
•
• Web JSON YAML……

9. Haskeller
•
• Web JSON YAML……
•

10. Haskeller
•
• Web JSON YAML……
•
• Java C

11. Haskeller
•
• Web JSON YAML……
•
• Java C
•

13. • Parser Pretty Printer

14. • Parser Pretty Printer
• Parser

15. • Parser Pretty Printer
• Parser
• (Parsec, Happy...)

16. • Parser Pretty Printer
• Parser
• (Parsec, Happy...)
•

17. • Parser Pretty Printer
• Parser
• (Parsec, Happy...)
•
• Pretty Printer

18. • Parser Pretty Printer
• Parser
• (Parsec, Happy...)
•
• Pretty Printer
• …… (Show, HughesPJ...)

19. • Parser Pretty Printer
• Parser
• (Parsec, Happy...)
•
• Pretty Printer
• …… (Show, HughesPJ...)
• ……

20. • Parser Pretty Printer
•
• Don’t Repeat Yourself!
• Pretty Printer
•
•

21. invertible-syntax

22. invertible-syntax
• Parser Pretty Printer
• Syntax Description
• Applicative
•
• Parser Pretty Printer

23. JSON

24. JSON
• JSON
•
•
data Slot = Slot { key :: String, val :: JSON }
data JSON = Number !Integer
| Null
| Bool !Bool
| Array ![JSON]
| String String
| Object ![Slot]

25. JSONPretty.hs
import Text.PrettyPrint.HughesPJ
pretty :: Printer JSON -- Printer a = a → Doc
pretty (Object jss) = braces $ hcat $ intersperse comma
$ map slot jss
pretty (Array jss) = brackets $ hcat $ intersperse comma
$ map pretty jss
pretty (String str) = doubleQuotes $ text str
pretty (Null) = text "null"
pretty (Bool b) = case b of
True → text "true"
False → text "false"
pretty (Number int) = integer int
slot s = doubleQuotes (text $ key s) <> colon <+> sub (val s)

26. JSONParsec.hs
import Text.Parsec
json, jsobj, ..., jsnumber :: Parser JSON
json = jsobj <|> jsarray <|> ... <|> jsbool <|> jsnumber
jsobj = Object <$> between (symbol "{") (symbol "}")
(term `sepBy` symbol ",")
where
term = Slot <$> str <* symbol ":" <*> json
jsarray = Array <$> between (symbol "[") (symbol "]")
(json `sepBy` symbol ",")
jsstring = String <$> str
jsnull = Null <$ symbol "null"
jsbool = Bool True <$ symbol "true"
<|> Bool False <$ symbol "false"
jsnumber = Number . read <$> many1 digit
str = between (spaces *> char '"') (char '"' <* spaces)
(many $ noneOf """)

27. JSONInvertible.hs
defineIsomorphisms ''JSON
json, jsobj, ..., jsnumber :: Syntax f f JSON
json = jsobj <|> jsarray <|> ... <|> jsbool <|> jsnumber
jsobj = object <$> between (symbol "{") (symbol "}")
(term `sepBy` symbol ",")
where
term = slot <$> str <* skipSpace <* text ":" <*> json
jsarray = array <$> between (symbol "[") (symbol "]")
(json `sepBy` symbol ",")
jsstring = string <$> str
jsnull = null <$> symbol "null"
jsbool = bool . element True <$> symbol "true"
<|> bool . element False <$> symbol "false"
jsnumber = number . numIso <$> many1 digit
str = between (optSpace *> text """) (text """ <* optSpace)
(many (subset (/='"') <$> token))
numIso = Iso read’ show’
where
read' = liftM fst . listToMaybe . reads
show' = return . show

29. • Syntax f f JSON
• Syntax Description
• pure token
• <$> <$ <*>

30. • defineIsomorphisms ……
•
• (<$) (<$>)
• Iso

31. Inside
invertible-sytnax

32. Parser Priner

33. Parser Priner
• Iso :

34. Parser Priner
• Iso :
• data Iso a b = Iso (a→Maybe b) (b→Maybe a)

35. Parser Priner
• Iso :
• data Iso a b = Iso (a→Maybe b) (b→Maybe a)
•

36. Parser Priner
• Iso :
• data Iso a b = Iso (a→Maybe b) (b→Maybe a)
•
• Iso Category

37. Parser Priner
• Iso :
• data Iso a b = Iso (a→Maybe b) (b→Maybe a)
•
• Iso Category
• id (.)

38. Parser Priner
• Iso :
• data Iso a b = Iso (a→Maybe b) (b→Maybe a)
•
• Iso Category
• id (.)
• IsoFunctor

39. Iso 1
numIso = Iso read’ show’
where
read' = liftM fst . listToMaybe . reads
show' = return . show
•
• Control.Isomorphism.Partial.Unsafe
•
• Iso

40. Iso 2
• import Control.Isomorphism.Partial
• element :: α → Iso α ()
• ()
• subset :: (α → Bool) → Iso α α
•
• foldl :: Iso (α,β) α → Iso (α,[β]) α
• (***), associate, iterate, unit ……

41. IsoFunctor
• Functor =
• fmap :: (α→β) → f α → f β
• α→β Iso α β …
class IsoFunctor δ where
(<$>) :: Iso α β → δ α → δ β
•

42. partial-isomorphisms

44. invertible-syntax
Applicative

45. invertible-syntax
Applicative

46. invertible-syntax
Applicative

47. • (<*>)
• (<*>) :: δ (α → β) → δ α → δ β
• Iso α β ……
class IsoApplicative δ where
(<*>) :: δ (Iso α β) → δ α → δ β
• Parser
• Iso α β α

48. Printer
instance IsoApplicative Printer where
(<*>) pab pa b = ……

49. Printer
instance IsoApplicative Printer where
(<*>) pab pa b = ……
• (<*>) :: Printer (Iso α β) → Printer α → Printer β
= ((Iso α β)→Doc) → (α→Doc) → β → Doc

50. Printer
instance IsoApplicative Printer where
(<*>) pab pa b = ……
• (<*>) :: Printer (Iso α β) → Printer α → Printer β
= ((Iso α β)→Doc) → (α→Doc) → β → Doc
•β

51. Printer
instance IsoApplicative Printer where
(<*>) pab pa b = ……
• (<*>) :: Printer (Iso α β) → Printer α → Printer β
= ((Iso α β)→Doc) → (α→Doc) → β → Doc
•β
• ……

52. Printer
instance IsoApplicative Printer where
(<*>) pab pa b = ……
• (<*>) :: Printer (Iso α β) → Printer α → Printer β
= ((Iso α β)→Doc) → (α→Doc) → β → Doc
•β
• ……
• ……

54. • Applicative

55. • Applicative
• Slot <$> key <*> val

56. • Applicative
• Slot <$> key <*> val
• Slot :: String → JSON → (String, JSON)

57. • Applicative
• Slot <$> key <*> val
• Slot :: String → JSON → (String, JSON)
• slot :: Iso String (Iso JSON Slot)

58. • Applicative
• Slot <$> key <*> val
• Slot :: String → JSON → (String, JSON)
• slot :: Iso String (Iso JSON Slot)
• slot <$> key :: δ (Iso JSON Slot)

59. ……

60. ……
• slot :: Iso (String, JSON) Slot

61. ……
• slot :: Iso (String, JSON) Slot
• slot <$> key <*> val :: δ Slot
……

62. ……
• slot :: Iso (String, JSON) Slot
• slot <$> key <*> val :: δ Slot
……
• slot <$> (key <*> val) ……

63. ……
• slot :: Iso (String, JSON) Slot
• slot <$> key <*> val :: δ Slot
……
• slot <$> (key <*> val) ……
• (<*>) :: δ α → δ β → δ (α, β)

64. ProductFunctor
class ProductFunctor δ where
(<*>) :: δ α → δ β → δ (α, β)
infix 5 <$>
infixr 6 <*>
• Parser Printer
•

65. Iso
null :: Iso () JSON
null = Iso to from
where
to _ = Just Null
from Null = Just ()
from _ = Nothing
number :: Iso Integer JSON
number = Iso to from
where
to = Just . Number
from (Number int) = Just int
from _ = Nothing
slot :: Iso (String, JSON) Slot
slot = Iso to from
where
to (a,b) = Just $ Slot a b
from (Slot a b) = Just (a,b)

66. class Alternative δ where
(<|>) :: δ α → δ α → δ α
empty :: δ α
• Applicative instance
• token
• pure
• Syntax

68. class IsoFunctor δ where
(<$>) :: Iso α β → δ α → δ β
class ProductFunctor δ where
(<*>) :: δ α → δ β → δ (α, β)
class Alternative δ where
(<|>) :: δ α → δ α → δ α
empty :: δ α
class ( IsoFunctor δ, ProductFunctor δ
, Alternative δ
) Syntax δ where
pure :: α → δ α
token :: δ Char

70. •

71. •
• many, sepBy, chainl1, text, between

72. •
• many, sepBy, chainl1, text, between
• +

73. •
• many, sepBy, chainl1, text, between
• +
• skipSpace, sepSpace, optSpace

74. •
• many, sepBy, chainl1, text, between
• +
• skipSpace, sepSpace, optSpace
•

75. •
• many, sepBy, chainl1, text, between
• +
• skipSpace, sepSpace, optSpace
•
• Printer

76. •
• many, sepBy, chainl1, text, between
• +
• skipSpace, sepSpace, optSpace
•
• Printer
• sep opt

77. • skipSpace sepSpace optSpace
•
• “ntr”

78. read/show invertible-syntax
Parsec/HughesPJ ( )

79. •
• invertible-syntax Parser Printer
Naive
•
• Proof of Concept

81. • Parsec HughesPJ Syntax

82. • Parsec HughesPJ Syntax
•

83. • Parsec HughesPJ Syntax
•
• (<|>)

84. • Parsec HughesPJ Syntax
•
• (<|>)
•

85. • Parsec HughesPJ Syntax
•
• (<|>)
•
•

86. • Parsec HughesPJ Syntax
•
• (<|>)
•
•
•

88. ADT Iso

89. defineIsomorphisms

90. Real World
Template Haskell
defineIsomorphisms TH

91. null :: Iso () JSON
null = Iso to from
where
to _ = Just Null
from Null = Just ()
from _ = Nothing
number :: Iso Integer JSON
number = Iso to from
where
to a = Just $ Number a
from (Number int) = Just int
from _ = Nothing
slot :: Iso (String, JSON) Slot
slot = Iso to from
where
to (a,b) = Just $ Slot a b
from (Slot a b) = Just (a,b)

92. • data Hoge
•
• Iso () Hoge
• Iso (a, (b, ...)) Hoge

93. • from
• Just $ a b c ...
• to
•
Nothing
•

94. •
• reify
•
• …… Exp
• …… Type

95. TH
• Metaprogramming in Haskell

96. •
•
• E ,P ,T ,D ,
C , B Body, L
• type HogeQ = Q Hoge
• (LamE lamE )
• Q
• lamE :: [PatQ] → ExpQ→ ExpQ

97. • defineIsomorphisms :: Name → Q [Dec]
• data newtype
defineIsomorphisms :: Name → Q [Dec]
defineIsomorphisms d = do
TyConI dec ← reify d
cs ← decConstructors dec
mapM (defFromCon (wildcard cs)) cs
decConstructors :: Dec -> Q [Con]
decConstructors (DataD _ _ _ cs _) = return cs
decConstructors (NewtypeD _ _ _ c _)= return [c]
decConstructors _ = error “not supported!”

98. • wildcard
• case { _ → Nothing }
• defFromCon
• rename ( )
wildcard :: [Con] -> [MatchQ]
wildcard cs
= if length cs > 1
then [match (wildP) (normalB [| Nothing |]) []]
else []
defFromCon :: [MatchQ] -> Con -> DecQ
defFromCon wc con
= funD (rename (conName con))
[clause [] (normalB (isoFromCon wc con)) []]

99. •
isoFromCon :: [MatchQ] -> Con -> ExpQ
Iso
isoFromCon wildcard con = do
let c = conName con
let fs = conFields con --
let n = length fs --
(ps, vs) ← genPE n --
v ← newName "x"
let f = lamE [nested tupP ps] --
[| Just $(foldl appE (conE c) vs) |]
let g = lamE [varP v]
(caseE (varE v) $
[ match (conP c ps) -- Con (a,(b,..) →
(normalB [| Just $(nested tupE vs) |]) []
] ++ wildcard) -- case
[| Iso $f $g |] -- from/to λ Iso

100. Any Questions?