{-# LINE 1 "Propositional/AS_BASIC_Propositional.der.hs" #-}

{-# OPTIONS -fallow-undecidable-instances #-}

{- |

Module : $Header$

Description : Instance of class Logic for propositional logic

Copyright : (c) Dominik Luecke, Uni Bremen 2007

License : similar to LGPL, see HetCATS/LICENSE.txt or LIZENZ.txt

Maintainer : luecke@tzi.de

Stability : experimental

Portability : portable

Definition of abstract syntax for propositional logic

Ref.

-}

module Propositional.AS_BASIC_Propositional where

import Common.Id

-- DrIFT command

{-! global: UpPos !-}

data Formula f = Negation (Formula f) Range

-- pos: not

| Conjunction [Formula f] Range

-- pos: "/\"s

| Disjunction [Formula f] Range

-- pos: "\/"s

| Implication (Formula f) (Formula f) Bool Range

-- pos: "=>"

| Equivalence (Formula f) (Formula f) Bool Range

-- pos: "<=>"

| True_atom Range

-- pos: "True"

| False_atom Range

-- pos: "False

| Predication Common.Id.Id

-- pos: Propositional Identifiers

deriving (Show, Eq, Ord)

-- True is always true -P

is_True_atom :: Formula f -> Bool

is_True_atom (True_atom _) = True

is_True_atom _ = False

-- and False if always false

is_False_atom :: Formula f -> Bool

is_False_atom (False_atom _) = False

is_False_atom _ = False

{- ? Generated by DrIFT : Look, but Don't Touch. ? -}

instance PosItem f => PosItem (Formula f) where

getRange (Negation _ p) = p

getRange (Conjunction _ p) = p

getRange (Disjunction _ p) = p

getRange (Implication _ _ _ p) = p

getRange (Equivalence _ _ _ p) = p

getRange (True_atom p) = p

getRange (False_atom p) = p

getRange (Predication _) = nullRange

-- Imported from other files :-