{- |

Module : $Header$

Description : supply a default morphism for a given signature type

Copyright : (c) C. Maeder, and Uni Bremen 2002-2006

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

Maintainer : Christian.Maeder@dfki.de

Stability : provisional

Portability : portable

Supply a default morphism for a given signature type

-}

-- due to functional deps the instance for Logic.Category cannot be supplied

module Common.DefaultMorphism

( DefaultMorphism(..) -- constructor is only exported for ATC

, ideOfDefaultMorphism

, compOfDefaultMorphism

, legalDefaultMorphism

, defaultInclusion

) where

import Common.Keywords

import Common.Doc

import Common.DocUtils

data DefaultMorphism sign = MkMorphism

{ domOfDefaultMorphism :: sign

, codOfDefaultMorphism :: sign

} deriving (Show, Eq, Ord)

instance Pretty a => Pretty (DefaultMorphism a) where

pretty = printDefaultMorphism pretty

printDefaultMorphism :: (a -> Doc) -> DefaultMorphism a -> Doc

printDefaultMorphism fA (MkMorphism s t) =

text "inclusion" $+$ specBraces (fA s) $+$ text mapsTo <+> specBraces (fA t)

ideOfDefaultMorphism :: sign -> DefaultMorphism sign

ideOfDefaultMorphism s = MkMorphism s s

compOfDefaultMorphism :: Monad m => DefaultMorphism sign

-> DefaultMorphism sign -> m (DefaultMorphism sign)

compOfDefaultMorphism (MkMorphism s1 _) (MkMorphism _ s3) =

return $ MkMorphism s1 s3

legalDefaultMorphism :: (sign -> Bool) -> DefaultMorphism sign -> Bool

legalDefaultMorphism legalSign (MkMorphism s t) = legalSign s && legalSign t

defaultInclusion :: Monad m => sign -> sign -> m (DefaultMorphism sign)

defaultInclusion s = return . MkMorphism s