praxis

commit 8ff6023634a134776667a3c24897f2bd9ba3b65a
parent ee6bf11cdfe63185ea054ac00c78786347aa35cf
Author: Jared Tobin <jared@jtobin.ca>
Date:   Tue, 10 Jul 2018 09:52:32 +1200

Add embedded numbers thing.

Diffstat:
A
20180515_embedded/Number.hs
 | 
48
++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 48 insertions(+), 0 deletions(-)
diff --git a/20180515_embedded/Number.hs b/20180515_embedded/Number.hs
@@ -0,0 +1,48 @@
+{-# OPTIONS_GHC -Wall #-}
+
+import Data.Char as C
+
+esum :: String -> Int
+esum = sum . grab
+
+grab :: String -> [Int]
+grab = loop [] Nothing where
+  loop acc prev list = case list of
+    []          -> reverse $ case prev of
+      Nothing  -> acc
+      Just num ->
+        let parsed = parse (reverse num)
+        in  parsed : acc
+
+    (curr:rest) -> case prev of
+      Nothing ->
+        if   C.isDigit curr
+        then loop acc (Just [curr]) rest
+        else loop acc Nothing rest
+
+      Just num ->
+        if   C.isDigit curr
+        then loop acc (Just (curr : num)) rest
+        else
+          let parsed = parse (reverse num)
+          in  loop (parsed : acc) Nothing rest
+
+parse :: String -> Int
+parse =
+    snd . foldr alg (1, 0)
+  where
+    alg char (base, acc) =
+      let nbase = base * 10
+          nacc  = acc + C.digitToInt char * base
+      in  (nbase, nacc)
+
+test0 :: String
+test0 = "11aa22bb33cc44"
+
+test1 :: String
+test1 = "1k23jk34jk56jk3454"
+
+main :: IO ()
+main = do
+  print (esum test0)
+  print (esum test1)