PRELUSE: add sortLexSwapped

2015-01-08 01:38:32 +01:00 · 2015-01-08 01:38:32 +01:00 · 79175d7fa0
commit 79175d7fa0
parent 1dd4dd6f59
1 changed files with 8 additions and 0 deletions
--- a/MyPrelude.hs
+++ b/MyPrelude.hs
@ -40,6 +40,14 @@ sortLex =
           x  -> x)


+-- |Sort a list of tuples lexicographically, but start with second elem.
+sortLexSwapped :: (Ord a) => [(a, a)] -> [(a, a)]
+sortLexSwapped =
+  sortBy (\(x1, y1) (x2, y2) -> case compare y1 y2 of
+           EQ -> compare x1 x2
+           y  -> y)
+
+
 -- |Get the last x elements of a list.
 getLastX :: Int -> [a] -> [a]
 getLastX a xs