{- |

Module : $Header$

Copyright : (c) Christian Maeder, Uni Bremen 2004

Licence : similar to LGPL, see HetCATS/LICENCE.txt or LIZENZ.txt

Maintainer : till@tzi.de

Stability : provisional

Portability : portable

data types for amalgamability options and analysis

-}

module Common.Amalgamate where

import Data.List

{- | 'CASLAmalgOpt' describes the options for CASL amalgamability analysis

algorithms -}

data CASLAmalgOpt = Sharing -- ^ perform the sharing checks

| ColimitThinness -- ^ perform colimit thinness check (implies Sharing)

| Cell -- ^ perform cell condition check (implies Sharing)

| NoAnalysis -- ^ dummy option to indicate empty option string

-- | Amalgamability analysis might be undecidable, so we need

-- a special type for the result of ensures_amalgamability

data Amalgamates = Amalgamates

| NoAmalgamation String -- ^ failure description

| DontKnow String -- ^ the reason for unknown status

-- | The default value for 'DontKnow' amalgamability result

defaultDontKnow :: Amalgamates

defaultDontKnow = DontKnow "Unable to assert that amalgamability is ensured"

instance Show CASLAmalgOpt where

show o = case o of

Sharing -> "sharing"

ColimitThinness -> "colimit-thinness"

Cell -> "cell"

NoAnalysis -> "none"

instance Read CASLAmalgOpt where

readsPrec _ = readShow caslAmalgOpts

-- | input all possible values and read one as it is shown

readShow :: Show a => [a] -> ReadS a

readShow l s = case find ( \ o -> isPrefixOf (show o) s) l of

Nothing -> []

Just t -> [(t, drop (length $ show t) s)]

-- | possible CASL amalgamability options

caslAmalgOpts :: [CASLAmalgOpt]

caslAmalgOpts = [NoAnalysis, Sharing, Cell, ColimitThinness]