compiler/SourceSyntax/Pattern.hs · elk

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1{-# LANGUAGE DeriveDataTypeable #-}

2module SourceSyntax.Pattern where

4import Data.Char (isDigit)

5import Data.List (intercalate)

6import Data.Data

7import SourceSyntax.Helpers

8import qualified SourceSyntax.Literal as Literal

10data Pattern = PData String [Pattern]

11 | PRecord [String]

12 | PAlias String Pattern

13 | PVar String

14 | PAnything

15 | PLiteral Literal.Literal

16 deriving (Eq, Data, Typeable)

18cons h t = PData "Cons" [h,t]

19nil = PData "Nil" []

20list = foldr cons nil

21tuple es = PData ("Tuple" ++ show (length es)) es

24instance Show Pattern where

25 show p =

26 case p of

27 PVar x -> x

28 PLiteral lit -> show lit

29 PRecord fs -> brkt (intercalate ", " fs)

30 PAlias x p -> show p ++ " as " ++ x

31 PAnything -> "_"

32 PData "Cons" [hd@(PData "Cons" _),tl] ->

33 parens (show hd) ++ " :: " ++ show tl

34 PData "Cons" [hd,tl] -> show hd ++ " :: " ++ show tl

35 PData "Nil" [] -> "[]"

36 PData name ps ->

37 if take 5 name == "Tuple" && all isDigit (drop 5 name) then

38 parens . intercalate ", " $ map show ps

39 else parensIf (not (null ps)) $ unwords (name : map show ps)