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|
{-# LANGUAGE RecursiveDo #-}
module Felix.Syntax.Mixfix where
{-
Original code Copyright (c) 2014-2019, Olle Fredriksson
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials provided
with the distribution.
* Neither the name of Olle Fredriksson nor the names of other
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-}
import Base
import Text.Earley
import Data.Either
import Felix.Syntax.Abstract
replicateA :: Applicative f => Int -> f a -> f [a]
replicateA n = sequenceA . replicate n
consA :: Applicative f => f a -> f [a] -> f [a]
consA p q = (:) <$> p <*> q
-- | An identifier with identifier parts ('Just's), and holes ('Nothing's)
-- representing the positions of its arguments.
--
-- Example (commonly written "if_then_else_"):
-- @['Just' "if", 'Nothing', 'Just' "then", 'Nothing', 'Just' "else", 'Nothing'] :: 'Holey' 'String'@
type Holey a = [Maybe a]
-- | Create a grammar for parsing mixfix expressions.
mixfixExpression
:: [[(Holey (Prod r e t ident), Associativity)]]
-- ^ A table of holey identifier parsers, with associativity information.
-- The identifiers should be in groups of precedence levels listed from
-- binding the least to the most tightly.
--
-- The associativity is taken into account when an identifier starts or ends
-- with holes, or both. Internal holes (e.g. after "if" in "if_then_else_")
-- start from the beginning of the table.
--
-- Note that this rule also applies to identifiers with multiple consecutive
-- holes, e.g. "if__" --- the associativity then applies to both holes.
-> Prod r e t expr
-- ^ An atom, i.e. what is parsed at the lowest level. This will
-- commonly be a (non-mixfix) identifier or a parenthesised expression.
-> (Holey ident -> [expr] -> expr)
-- ^ How to combine the successful application of a holey identifier to its
-- arguments into an expression.
-> Grammar r (Prod r e t expr)
mixfixExpression table atom app = mixfixExpressionSeparate table' atom
where
table' = [[(holey, assoc, app) | (holey, assoc) <- row] | row <- table]
-- | A version of 'mixfixExpression' with a separate semantic action for each
-- individual 'Holey' identifier.
mixfixExpressionSeparate
:: [[(Holey (Prod r e t ident), Associativity, Holey ident -> [expr] -> expr)]]
-- ^ A table of holey identifier parsers, with associativity information and
-- semantic actions. The identifiers should be in groups of precedence
-- levels listed from binding the least to the most tightly.
--
-- The associativity is taken into account when an identifier starts or ends
-- with holes, or both. Internal holes (e.g. after "if" in "if_then_else_")
-- start from the beginning of the table.
--
-- Note that this rule also applies to identifiers with multiple consecutive
-- holes, e.g. "if__" --- the associativity then applies to both holes.
-> Prod r e t expr
-- ^ An atom, i.e. what is parsed at the lowest level. This will
-- commonly be a (non-mixfix) identifier or a parenthesised expression.
-> Grammar r (Prod r e t expr)
mixfixExpressionSeparate table atom = mdo
expr <- foldrM ($) atom $ map (level expr) table
return expr
where
level expr idents next = mdo
same <- rule $ asum $ next : map (mixfixIdent same) idents
return same
where
-- Group consecutive holes and ident parts.
grp [] = []
grp (Nothing:ps) = case grp ps of
Left n:rest -> (Left $! (n + 1)) : rest
rest -> Left 1 : rest
grp (Just p:ps) = case grp ps of
Right ps':rest -> Right (consA p ps') : rest
rest -> Right (consA p $ pure []) : rest
mixfixIdent same (ps, a, f) = f' <$> go (grp ps)
where
f' xs = f (concatMap (either (map $ const Nothing) $ map Just) xs)
$ concat $ lefts xs
go ps' = case ps' of
[] -> pure []
[Right p] -> pure . Right <$> p
Left n:rest -> consA
(Left <$> replicateA n (if a == RightAssoc then next
else same))
$ go rest
[Right p, Left n] -> consA
(Right <$> p)
$ pure . Left <$> replicateA n (if a == LeftAssoc then next
else same)
Right p:Left n:rest -> consA (Right <$> p)
$ consA (Left <$> replicateA n expr)
$ go rest
Right _:Right _:_ -> error
$ "Earley.mixfixExpression: The impossible happened. "
++ "Please report this as a bug."
|
