<div style="font-family: 'Times New Roman'; font-size: 16px;"><div _moz_dirty=""><div class="mimepart text html">Hi,<br />
Does the subclass relation have any meaning when two classes have instances with the same type?<br />
I get the same results from Listing 1 and Listing 2 below.<br />
Regards,<br />
Pat<br />
<br />
-- ====Listing 1- Subclass====<br />
data Shed = Shed <br />
<br />
class Building building where<br />
addressB :: building -> Integer<br />
addressB b = 1<br />
<br />
-- subclass, but none in Listing 2<br />
class Building house => House house where<br />
addressH :: house -> Integer<br />
addressH b = 0<br />
<br />
instance Building Shed where<br />
instance House Shed where<br />
<br />
<br />
-- ====Listing 2 -- No subclass====<br />
data Shed = Shed <br />
<br />
class Building building where<br />
addressB :: building -> Integer<br />
addressB b = 1<br />
<br />
-- No subclass <br />
class House house where<br />
addressH :: house -> Integer<br />
addressH b = 0<br />
<br />
instance Building Shed where<br />
instance House Shed where<br />
<br />
<br />
-- Test runs give same result for Listing 1 and Listing 2<br />
-- addressH Shed<br />
-- addressB Shed
</div></div></div>