all tasks

Task/Sorting-algorithms-Merge-sort/Curry/sorting-algorithms-merge-sort.curry

@@ -0,0 +1,30 @@
+-- merge sort: sorting two lists by merging the sorted first
+-- and second half of the list
+
+sort :: ([a] -> [a] -> [a] -> Success) -> [a] -> [a] -> Success
+
+sort merge xs ys =
+   if length xs < 2 then ys =:= xs
+   else sort merge (firsthalf xs) us
+        & sort merge (secondhalf xs) vs
+        & merge us vs ys
+   where us,vs free
+
+
+intMerge :: [Int] -> [Int] -> [Int] -> Success
+
+intMerge []     ys     zs =  zs =:= ys
+intMerge (x:xs) []     zs =  zs =:= x:xs
+intMerge (x:xs) (y:ys) zs =
+   if (x > y) then intMerge (x:xs) ys us & zs =:= y:us
+              else intMerge xs (y:ys) vs & zs =:= x:vs
+   where us,vs free
+
+firsthalf  xs = take (length xs `div` 2) xs
+secondhalf xs = drop (length xs `div` 2) xs
+
+
+
+goal1 xs = sort intMerge [3,1,2] xs
+goal2 xs = sort intMerge [3,1,2,5,4,8] xs
+goal3 xs = sort intMerge [3,1,2,5,4,8,6,7,2,9,1,4,3] xs