praxis

commit 0ee3cac16b00e454bdd54cf3bcd4b34aa4c57c5f
parent 8ff6023634a134776667a3c24897f2bd9ba3b65a
Author: Jared Tobin <jared@jtobin.ca>
Date:   Wed, 11 Jul 2018 14:21:42 +1200

Add uniques thing.

Diffstat:
A
20180711_uniques/Uniques.hs
 | 
29
+++++++++++++++++++++++++++++

1 file changed, 29 insertions(+), 0 deletions(-)
diff --git a/20180711_uniques/Uniques.hs b/20180711_uniques/Uniques.hs
@@ -0,0 +1,29 @@
+{-# OPTIONS_GHC -Wall #-}
+
+import qualified Data.Set as S
+import qualified Data.List as L
+
+allUniqueFast :: String -> Bool
+allUniqueFast = loop mempty where
+  loop set input = case input of
+    []           -> True
+    (char:chars) ->
+         not (S.member char set)
+      && loop (S.insert char set) chars
+
+allUniqueSlow :: String -> Bool
+allUniqueSlow = loop Nothing . L.sort where
+  loop acc input = case input of
+    []           -> True
+    (char:chars) -> case acc of
+      Nothing   -> loop (Just char) chars
+      Just prev ->
+             (char /= prev)
+          && loop (Just char) chars
+
+pour :: [a] -> [a]
+pour = loop mempty where
+  loop acc input = case input of
+    []    -> acc
+    (h:t) -> loop (h:acc) t
+