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Avoid recomputing the lengths.

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This commit is contained in:
Rob Rix 2017-06-13 18:13:48 -04:00
parent cebdbf2e0c
commit 9b916d3619
1 changed files with 8 additions and 8 deletions
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16
src/SES/Myers.hs
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@ -64,9 +64,10 @@ runSES eq (EditGraph as bs)
| null bs = return (This <$> toList as)
| null as = return (That <$> toList bs)
| otherwise = do
Just (script, _) <- for [0..(length as + length bs)] (searchUpToD . Distance)
Just (script, _) <- for [0..(n + m)] (searchUpToD . Distance)
return (reverse script)
where
where (n, m) = (length as, length bs)
-- | Search an edit graph for the shortest edit script up to a given proposed edit distance, building on the results of previous searches.
searchUpToD (Distance d) =
for [ k | k <- [negate d, negate d + 2 .. d], inRange (negate m, n) k ] (searchAlongK (Distance d) . Diagonal)
@ -75,7 +76,7 @@ runSES eq (EditGraph as bs)
-- | Search an edit graph for the shortest edit script along a specific diagonal.
searchAlongK d k = do
Endpoint x y script <- moveFromAdjacent d k
return $! if x >= length as && y >= length bs then
return $! if x >= n && y >= m then
Just (script, d)
else
Nothing
@ -84,7 +85,6 @@ runSES eq (EditGraph as bs)
moveFromAdjacent (Distance d) (Diagonal k) = do
v <- get
let getK k = let (x, script) = v ! k in Endpoint x (x - unDiagonal k) script
let (n, m) = (length as, length bs)
let endpoint@(Endpoint x' _ script) = slideFrom $! if d == 0 || k < negate m || k > n then
-- The top-left corner, or otherwise out-of-bounds.
Endpoint 0 0 []
@ -106,15 +106,15 @@ runSES eq (EditGraph as bs)
return endpoint
-- | Move downward from a given vertex, inserting the element for the corresponding row.
moveDownFrom (Endpoint x y script) = Endpoint x (succ y) (if y < length bs then That (bs ! y) : script else script)
moveDownFrom (Endpoint x y script) = Endpoint x (succ y) (if y < m then That (bs ! y) : script else script)
-- | Move rightward from a given vertex, deleting the element for the corresponding column.
moveRightFrom (Endpoint x y script) = Endpoint (succ x) y (if x < length as then This (as ! x) : script else script)
moveRightFrom (Endpoint x y script) = Endpoint (succ x) y (if x < n then This (as ! x) : script else script)
-- | Slide down any diagonal edges from a given vertex.
slideFrom (Endpoint x y script)
| x >= 0, x < length as
, y >= 0, y < length bs
| x >= 0, x < n
, y >= 0, y < m
, a <- as ! x
, b <- bs ! y
, a `eq` b = slideFrom (Endpoint (succ x) (succ y) (These a b : script))