the destination string. The convention is
edit :: Eq a => Cursor a -> Cursor a -> [Move]
- 1. If both strings have been consumed, then no moves are to be made.
edit (cdone -> True) (cdone -> True) = 
- 2. If the destination string has been fully matched while the source string has not, then remove characters from the source string.
edit a@(cdone -> False) b@(cdone -> True) =
(RemoveFromSrc (cix a)):edit (incr a) b
- 3. If the source string has run out of characters while the destination string still has characters, insert characters from the destination string.
edit a@(cdone -> True) b@(cdone -> False) =
(InsertFromDest (cix b)):edit a (incr b)
- 4. Otherwise, we have characters remaining in both strings. Try the options of (1) replacing a source character with a destination character (2) removing a character from the source and continuing, and (3) if the current characters match, then keep the match and try to combine characters that come later in the string. We pick the best out of these using the
The helper used for finding minimum according to a cost model.
edit a b =
let nomatch = argmin movescost
(ReplaceSrcWithDest (cix a) (cix b):edit (incr a) (incr b))
(RemoveFromSrc (cix a):edit (incr a) b)
in case cval a == cval b of
True -> argmin movescost nomatch (edit (incr a) (incr b))
False -> nomatch
argmin :: (a -> Int) -> a -> a -> a
argmin f a a' = if (f a) < (f a') then a else a'