----------------------------------------------------------------

-- the Generic Model Parser Abstract Syntax

-- Copyright 2007, Lutz Schroeder and Georgel Calin

----------------------------------------------------------------

module GMPAS where

----------------------------------------------------------------

-- Abstract Syntax

----------------------------------------------------------------

data Otype = Square | Angle -- type of the Modal Operator

data Junctor = And | Or | If | Fi | Iff

data Mop a = Mop a Otype -- Modal Operator: index & type

data Formula a = F -- datatype for the formulae

| T

| Neg (Formula a)

| Junctor (Formula a) Junctor (Formula a)

| Mapp (Mop a) (Formula a) -- modal application constructor

----------------------------------------------------------------

-- Print Abstract Syntax

----------------------------------------------------------------

instance Show a => Show (Mop a) where

show m = case m of

Mop x Square -> "[" ++ show x ++ "]"

Mop x Angle -> "<" ++ show x ++ ">"

instance Show Junctor where

show j = case j of

And -> "/\\"

Or -> "\\/"

If -> "->"

Fi -> "<-"

Iff -> "<->"

instance Show a => Show (Formula a) where

show f = case f of

F -> "F"

T -> "T"

Neg x -> "~" ++ show x

Junctor x j y -> "(" ++ show x ++ " " ++ show j ++ " " ++ show y ++ ")"

Mapp m x -> show m ++ " " ++ show x