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Atoms.hs
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Atoms.hs
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-- This file is part of FairCheck
--
-- FairCheck is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published
-- by the Free Software Foundation, either version 3 of the License,
-- or (at your option) any later version.
--
-- FairCheck is distributed in the hope that it will be useful, but
-- WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-- General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with FairCheck. If not, see <http://www.gnu.org/licenses/>.
--
-- Copyright 2021 Luca Padovani
-- |This module defines the representation of __identifiers__ and
-- __polarities__.
module Atoms where
-- |A position refers to line and column within a script. The constructor
-- 'Somewhere' builds an unknown position.
data Pos = Somewhere
| At (Int, Int)
instance Show Pos where
show Somewhere = ""
show (At (l, c)) = " [line " ++ show l ++ "]"
-- |The kind of labels.
data LabelI
-- |The kind of type names.
data TypeI
-- |The kind of channel names.
data ChannelI
-- |The kind of process names.
data ProcessI
-- |The 'Identifier' data type represents the occurrence of an identifier within
-- a script. It is a phantom type whose type parameter indicates the kind of the
-- identifier.
data Identifier k = Identifier { identifierPos :: Pos
, identifierText :: String }
instance Show (Identifier k) where
show = identifierText
-- |Show an identifier along with its position in the source code, if known.
showWithPos :: Identifier k -> String
showWithPos u = identifierText u ++ show (identifierPos u)
-- |Two identifiers are the same regardless of the position in which they occur.
instance Eq (Identifier k) where
(==) u v = identifierText u == identifierText v
-- |Two identifiers are ordered regardless of the position in which they occur.
instance Ord (Identifier k) where
compare u v = compare (identifierText u) (identifierText v)
-- |The type of labels.
type Label = Identifier LabelI
-- |The type of channel names.
type ChannelName = Identifier ChannelI
-- |The type of type names.
type TypeName = Identifier TypeI
-- |The type of process names.
type ProcessName = Identifier ProcessI
-- |A polarity describes the kind of action performed on a channel.
data Polarity
-- |Input action (question mark in the paper)
= In
-- |Output action (exclamation mark in the paper)
| Out
deriving (Eq, Ord)
-- |Compute the dual or opposite polarity.
dualP :: Polarity -> Polarity
dualP In = Out
dualP Out = In
instance Show Polarity where
show In = "?"
show Out = "!"