On Sat, 14 Nov 2009, Jason Dagit wrote:
Sat Nov 14 14:31:05 PST 2009 Jason Dagit <[email protected]>
* clean up elegant_merge
-elegant_merge (p1 :\/: p2) =
- case commutex (p1 :< invert p2) of
- Just (ip2':<p1') -> case commutex (p1' :< p2) of
- Nothing -> Nothing -- should be a redundant check
- Just (_:<p1o) -> if unsafeCompare p1o p1
- then Just (invert ip2' :/\: p1')
- else Nothing
- Nothing -> Nothing
+elegant_merge (p1 :\/: p2) = do
+ ip2' :< p1' <- commutex (p1 :< invert p2)
+ _ :< p1o <- commutex (p1' :< p2)
+ if unsafeCompare p1o p1 -- should be a redundant check
+ then return $ invert ip2' :/\: p1'
+ else Nothing
You've moved the "should be a redundant check" comment from the second
commutex call to the unsafeCompare. I guess that the comment really
should cover both of these things, do you agree?
BTW the code could be further elegantised by using "guard".
If you agree about the comment, I suggest I accept this patch as it
stands, particularly since other stuff depends on it, and one of us sends
a follow-on to clarify the comment.
Sat Nov 14 14:42:43 PST 2009 Jason Dagit <[email protected]>
* replace commutex with commute in elegant_merge
Looks fine.
Ganesh
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