Errata for "Pearls of Functional Algorithm Design" by Richard Bird,
2010, page 25 #Haskell
smallest :: (Ord a) => Int -> (Array Int a, Array Int a) -> a
smallest k (xa,ya) = search k (0,m+1) (0,n+1)
where
(0,m) = bounds xa
(0,n) = bounds ya
search k (lx,rx) (ly,ry)
| lx == rx = ya ! (k+ly)
| ly == ry = xa ! (k+lx)
| otherwise = case (xa ! mx < ya ! my, k
<= mx-lx+my-ly) of
(True, True) -> search
k (lx,rx) (ly,my)
(True, False) -> search
(k-(mx-lx)-1) (mx+1,rx) (ly,ry)
(False, True) -> search
k (lx,mx) (ly,ry)
(False, False)-> search
(k-(my-ly)-1) (lx,rx) (my+1,ry)
where
mx = (lx+rx) `div` 2
my = (ly+ry) `div` 2
--
--
Regards,
KC
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