```module Satchmo.Relation.Prop

( implies
, symmetric
, transitive
, irreflexive
, reflexive
, regular
)

where

import Prelude hiding ( and, or, not, product )
import qualified Prelude

import Satchmo.Code
import Satchmo.Boolean
import Satchmo.Counting
import Satchmo.Relation.Data
import Satchmo.Relation.Op

import Data.Ix

implies :: ( Ix a, Ix b, MonadSAT m )
=> Relation a b -> Relation a b -> m Boolean
implies r s = monadic and \$ do
i <- indices r
return \$ or [ not \$ r ! i, s ! i ]

symmetric :: ( Ix a, MonadSAT m) => Relation a a -> m Boolean
symmetric r = implies r ( mirror r )

irreflexive :: ( Ix a, MonadSAT m) => Relation a a -> m Boolean
irreflexive r = and \$ do
let ((a,b),(c,d)) = bounds r
x <- range ( a, c)
return \$ Satchmo.Boolean.not \$ r ! (x,x)

reflexive :: ( Ix a, MonadSAT m) => Relation a a -> m Boolean
reflexive r = and \$ do
let ((a,b),(c,d)) = bounds r
x <- range (a,c)
return \$ r ! (x,x)

regular :: ( Ix a, MonadSAT m) => Int -> Relation a a -> m Boolean
regular deg r = monadic and \$ do
let ((a,b),(c,d)) = bounds r
x <- range ( a , c )
return \$ exactly deg \$ do
y <- range (b,d)
return \$ r !(x,y)

transitive :: ( Ix a, MonadSAT m )
=> Relation a a -> m Boolean
transitive r = do
r2 <- product r r
implies r2 r
```