symantic-grammar/Language/Symantic/Grammar/EBNF.hs

   1 module Language.Symantic.Grammar.EBNF where
   2
   3 import Control.Applicative (Applicative(..))
   4 import Control.Monad
   5 import Data.Semigroup
   6 import Data.Text (Text)
   7 import qualified Data.Text as Text
   8
   9 import Language.Symantic.Grammar.Meta
  10 import Language.Symantic.Grammar.Fixity
  11
  12 -- * Type 'EBNF'
  13 -- | Extended Backus-Naur-Form, following the
  14 -- <http://standards.iso.org/ittf/PubliclyAvailableStandards/s026153_ISO_IEC_14977_1996(E).zip ISO-IEC-14977>
  15 -- notations, augmented with the following notations:
  16 --
  17 -- * @("U+", code_point)@: for <http://unicode.org/versions/Unicode8.0.0/ ISO-IEC-10646> (aka. Unicode).
  18 -- * @(char, "…", char)@: for character range.
  19 -- * @(rule, "&", rule)@: for the intersection.
  20 -- * @(rule, "-", rule)@: for the difference.
  21 -- * @(rule, " ", rule)@: for rule application.
  22 --
  23 -- Inherited attributes are:
  24 --
  25 -- * 'RuleMode' is the requested rendering mode of a 'Rule' (body or reference).
  26 -- * 'Infix' and 'Side' are the properties of the parent operator,
  27 --   used to enclose the operand in parenthesis only when needed.
  28 --
  29 -- Synthetized attributes are:
  30 --
  31 -- * 'Text' of the 'EBNF' rendition.
  32 newtype EBNF a = EBNF { unEBNF :: RuleMode -> (Infix, Side) -> Text }
  33 instance Gram_Reader st EBNF where
  34         askBefore (EBNF e) = EBNF e
  35         askAfter  (EBNF e) = EBNF e
  36 instance Gram_State st EBNF where
  37         stateBefore (EBNF e) = EBNF e
  38         stateAfter  (EBNF e) = EBNF e
  39 instance Gram_Error err EBNF where
  40         catch (EBNF e) = EBNF e
  41
  42 -- | Get textual rendition of given 'EBNF'.
  43 runEBNF :: EBNF a -> Text
  44 runEBNF (EBNF g) = g RuleMode_Body (infixN0, SideL)
  45
  46 -- | Get textual rendition of given 'RuleEBNF'.
  47 renderEBNF :: RuleEBNF a -> Text
  48 renderEBNF = runEBNF . unRuleEBNF
  49
  50 -- | 'EBNF' returns a constant rendition.
  51 ebnf_const :: Text -> EBNF a
  52 ebnf_const t = EBNF $ \_rm _op -> t
  53
  54 -- | 'EBNF' which adds an argument to be applied.
  55 ebnf_arg :: EBNF a -> EBNF b -> EBNF ()
  56 ebnf_arg (EBNF a) (EBNF b) = EBNF $ \bo po -> parenInfix po op $
  57         a bo (op, SideL) <> " " <> b bo (op, SideR)
  58         where op = infixL 11
  59 infixl 5 `ebnf_arg`
  60
  61 -- ** Type 'RuleMode'
  62 data RuleMode
  63  =   RuleMode_Body -- ^ Request to generate the body of the rule.
  64  |   RuleMode_Ref  -- ^ Request to generate a reference to the rule.
  65  deriving (Eq, Show)
  66
  67 -- * Type 'Rule'
  68 type Rule a = a -> a
  69
  70 -- ** Class 'Gram_Rule'
  71 class Gram_Rule g where
  72         rule :: Text -> Rule (g a)
  73         rule _n = id
  74         rule1 :: Text -> Rule (g a -> g b)
  75         rule1 _n g = g
  76         rule2 :: Text -> Rule (g a -> g b -> g c)
  77         rule2 _n g = g
  78         rule3 :: Text -> Rule (g a -> g b -> g c -> g d)
  79         rule3 _n g = g
  80         rule4 :: Text -> Rule (g a -> g b -> g c -> g d -> g e)
  81         rule4 _n g = g
  82
  83 -- * Type 'RuleEBNF'
  84 newtype RuleEBNF a = RuleEBNF { unRuleEBNF :: EBNF a }
  85  deriving (Functor, Applicative)
  86 deriving instance Gram_RuleEBNF RuleEBNF
  87 deriving instance Gram_Error err RuleEBNF
  88 deriving instance Gram_Reader st RuleEBNF
  89 deriving instance Gram_State st RuleEBNF
  90 instance Gram_Rule RuleEBNF where
  91         rule  n           = ruleEBNF (ebnf_const n)
  92         rule1 n g a       = ruleEBNF (ebnf_const n `ebnf_arg` unRuleEBNF a) (g a)
  93         rule2 n g a b     = ruleEBNF (ebnf_const n `ebnf_arg` unRuleEBNF a `ebnf_arg` unRuleEBNF b) (g a b)
  94         rule3 n g a b c   = ruleEBNF (ebnf_const n `ebnf_arg` unRuleEBNF a `ebnf_arg` unRuleEBNF b `ebnf_arg` unRuleEBNF c) (g a b c)
  95         rule4 n g a b c d = ruleEBNF (ebnf_const n `ebnf_arg` unRuleEBNF a `ebnf_arg` unRuleEBNF b `ebnf_arg` unRuleEBNF c `ebnf_arg` unRuleEBNF d) (g a b c d)
  96
  97 -- ** Class 'Gram_RuleEBNF'
  98 -- | Symantics for rendering 'EBNF' rules.
  99 --
 100 -- * 'ruleEBNF' renders a rule, either its body or a reference to it, according to 'RuleMode'.
 101 -- * 'argEBNF' renders an argument.
 102 class Gram_RuleEBNF g where
 103         ruleEBNF :: EBNF () -> g a -> RuleEBNF a
 104         argEBNF  :: Text -> g a
 105 instance Show (EBNF a) where
 106         show = Text.unpack . runEBNF
 107 instance Functor EBNF where
 108         fmap _f (EBNF x) = EBNF x
 109 instance Applicative EBNF where
 110         pure _ = ebnf_const $ "\"\""
 111         EBNF f <*> EBNF x = EBNF $ \bo po -> parenInfix po op $
 112                 f bo (op, SideL) <> ", " <> x bo (op, SideR)
 113                 where op = infixB SideL 10
 114 instance Gram_Rule EBNF where
 115         rule n g = EBNF $ \rm po ->
 116                 case rm of
 117                  RuleMode_Body -> unEBNF g RuleMode_Ref po
 118                  RuleMode_Ref  -> n
 119         rule1 n g a = EBNF $ \rm po ->
 120                 case rm of
 121                  RuleMode_Body -> unEBNF (g a) RuleMode_Ref po
 122                  RuleMode_Ref  -> unEBNF (ebnf_const n `ebnf_arg` a) RuleMode_Ref po
 123         rule2 n g a b = EBNF $ \rm po ->
 124                 case rm of
 125                  RuleMode_Body -> unEBNF (g a b) RuleMode_Ref po
 126                  RuleMode_Ref  -> unEBNF (ebnf_const n `ebnf_arg` a `ebnf_arg` b) RuleMode_Ref po
 127         rule3 n g a b c = EBNF $ \rm po ->
 128                 case rm of
 129                  RuleMode_Body -> unEBNF (g a b c) RuleMode_Ref po
 130                  RuleMode_Ref  -> unEBNF (ebnf_const n `ebnf_arg` a `ebnf_arg` b `ebnf_arg` c) RuleMode_Ref po
 131         rule4 n g a b c d = EBNF $ \rm po ->
 132                 case rm of
 133                  RuleMode_Body -> unEBNF (g a b c d) RuleMode_Ref po
 134                  RuleMode_Ref  -> unEBNF (ebnf_const n `ebnf_arg` a `ebnf_arg` b `ebnf_arg` c `ebnf_arg` d) RuleMode_Ref po
 135 instance Gram_RuleEBNF EBNF where
 136         argEBNF = ebnf_const
 137         ruleEBNF call body =
 138                 RuleEBNF $ EBNF $ \mo po ->
 139                         case mo of
 140                          RuleMode_Ref -> unEBNF call mo po
 141                          RuleMode_Body ->
 142                                 Text.intercalate " "
 143                                  [ unEBNF call RuleMode_Ref (infixN0, SideL)
 144                                  , "="
 145                                  , unEBNF body RuleMode_Ref (infixN0, SideR)
 146                                  , ";"
 147                                  ]