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https://github.com/idris-lang/Idris2.git
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1576a578a0
* contrib library unused import removal * remove a few unused imports. * another round of unused import removal * another round of unused import deletion. * another round of unused import deletion.
90 lines
2.9 KiB
Idris
90 lines
2.9 KiB
Idris
module Text.Parser.Expression
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import Text.Parser
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public export
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data Assoc
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= AssocNone
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| AssocLeft
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| AssocRight
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public export
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data Op state k a
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= Prefix (Grammar state k True (a -> a))
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| Postfix (Grammar state k True (a -> a))
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| Infix (Grammar state k True (a -> a -> a)) Assoc
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public export
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OperatorTable : Type -> Type -> Type -> Type
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OperatorTable state k a = List (List (Op state k a))
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export
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buildExpressionParser :
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OperatorTable state k a ->
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Grammar state k True a ->
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Grammar state k True a
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buildExpressionParser table term = foldl level term table
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where
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level : Grammar state k True a -> List (Op state k a) -> Grammar state k True a
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level factor ops = parseThese <|> factor
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where
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0 BinOp, UnOp : Type
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BinOp = Grammar state k True (a -> a -> a)
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UnOp = Grammar state k True (a -> a)
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0 SortedOps : Type
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SortedOps = (List BinOp, List BinOp, List BinOp, List UnOp, List UnOp)
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separate : Op state k a -> SortedOps -> SortedOps
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separate op (lassoc, rassoc, nassoc, pre, post) = case op of
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Infix p AssocLeft => (p::lassoc, rassoc, nassoc, pre, post)
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Infix p AssocRight => (lassoc, p::rassoc, nassoc, pre, post)
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Infix p AssocNone => (lassoc, rassoc, p::nassoc, pre, post)
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Prefix p => (lassoc, rassoc, nassoc, p::pre, post)
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Postfix p => (lassoc, rassoc, nassoc, pre, p::post)
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sortedOps : SortedOps
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sortedOps = foldr separate ([], [], [], [], []) ops
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parseThese : Grammar state k True a
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parseThese =
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let (lassoc, rassoc, nassoc, pre, post) = sortedOps
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termP : Grammar state k True a
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prefixP : Grammar state k False (a -> a)
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postfixP : Grammar state k False (a -> a)
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termP = do
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f <- prefixP
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x <- factor
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g <- postfixP
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pure $ g (f x)
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prefixP = choice pre <|> pure id
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postfixP = choice post <|> pure id
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rassocP : a -> Grammar state k True a
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rassocP1 : a -> Grammar state k False a
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rassocP x = do
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f <- choice rassoc
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y <- termP >>= rassocP1
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pure $ f x y
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rassocP1 x = rassocP x <|> pure x
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lassocP : a -> Grammar state k True a
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lassocP1 : a -> Grammar state k False a
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lassocP x = do
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f <- choice lassoc
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y <- termP
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lassocP1 $ f x y
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lassocP1 x = lassocP x <|> pure x
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nassocP : a -> Grammar state k True a
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nassocP x = do
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f <- choice nassoc
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y <- termP
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pure $ f x y
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in do
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x <- termP
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rassocP x <|> lassocP x <|> nassocP x <|> pure x
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