diff options
| author | tv <tv@shackspace.de> | 2015-01-13 00:46:04 +0100 |
|---|---|---|
| committer | tv <tv@shackspace.de> | 2015-01-13 00:47:51 +0100 |
| commit | d23ab0fa1510a9e5efccf6bdc7fbe524beef08e9 (patch) | |
| tree | a2e98006cb9d4bbef4badd1e94bf9ba861239c00 | |
| parent | 7adef3622630f37bcd7cc3dacd29fe6eea0df0a7 (diff) | |
find*N: skip successive items with same ID
| -rw-r--r-- | TreeSearch.hs | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/TreeSearch.hs b/TreeSearch.hs index 40b3c17..0a5df28 100644 --- a/TreeSearch.hs +++ b/TreeSearch.hs @@ -43,18 +43,18 @@ findPrev loc = -findNextN :: Int -> TreePos Full a -> TreePos Full a +findNextN :: Eq a => Int -> TreePos Full a -> TreePos Full a findNextN n loc | n <= 0 = loc | otherwise = - maybe loc (findNextN $ n - 1) (findNext loc) + maybe loc (findNextN $ n - 1) (skipSame findNext loc) -findPrevN :: Int -> TreePos Full a -> TreePos Full a +findPrevN :: Eq a => Int -> TreePos Full a -> TreePos Full a findPrevN n loc | n <= 0 = loc | otherwise = - maybe loc (findPrevN $ n - 1) (findPrev loc) + maybe loc (findPrevN $ n - 1) (skipSame findPrev loc) @@ -72,3 +72,18 @@ linearPos = rec i loc = case findPrev loc of Just loc' -> rec (i + 1) loc' Nothing -> i + + + +skipSame + :: Eq a => + (TreePos Full a -> Maybe (TreePos Full a)) -> + TreePos Full a -> + Maybe (TreePos Full a) +skipSame next loc = + case next loc of + Nothing -> Nothing + Just loc' -> + if label loc' == label loc + then skipSame next loc' + else Just loc' |