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Add a function to construct Maybe These from two Maybes.

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This commit is contained in:
Rob Rix 2016-03-31 14:45:04 -04:00
parent 84d49ed4e2
commit 2da930ae53
1 changed files with 6 additions and 0 deletions
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6
src/Alignment.hs
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@ -165,6 +165,12 @@ group2 ranges child | Just (headRanges, tailRanges) <- unconsThese ranges
atRight (Join (These as (b:bs))) = Join (These as bs)
atRight (Join (That (b:bs))) = Join (That bs)
atRight other = other
maybeThese :: (Maybe a, Maybe b) -> Maybe (These a b)
maybeThese (Just a, Just b) = Just (These a b)
maybeThese (Just a, _) = Just (This a)
maybeThese (_, Just b) = Just (That b)
maybeThese _ = Nothing
unconsThese :: Join These [a] -> Maybe (Join These a, Join These [a])
unconsThese (Join (This (a:as))) = Just (Join (This a), Join (This as))
unconsThese (Join (That (b:bs))) = Just (Join (That b), Join (That bs))