From f0881305402f3dff56f99fcc4cbc8b615581b780 Mon Sep 17 00:00:00 2001
From: Igor Pashev <pashev.igor@gmail.com>
Date: Sun, 28 Aug 2022 15:40:21 +0200
Subject: C, Haskell, Python, Fortran

---
 mendeleev.hs | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 mendeleev.hs

(limited to 'mendeleev.hs')

diff --git a/mendeleev.hs b/mendeleev.hs
new file mode 100644
index 0000000..cfd6ac5
--- /dev/null
+++ b/mendeleev.hs
@@ -0,0 +1,71 @@
+module Main
+  ( main
+  ) where
+
+import Data.Char (toLower)
+import System.Environment (getArgs)
+
+elements :: [String]
+elements = [
+  "Ac", "Ag", "Al", "Am", "Ar", "As", "At", "Au", "B", "Ba", "Be", "Bh",
+  "Bi", "Bk", "Br", "C", "Ca", "Cd", "Ce", "Cf", "Cl", "Cm", "Cn", "Co",
+  "Cr", "Cs", "Cu", "Db", "Ds", "Dy", "Er", "Es", "Eu", "F", "Fe", "Fl",
+  "Fm", "Fr", "Ga", "Gd", "Ge", "H", "He", "Hf", "Hg", "Ho", "Hs", "I",
+  "In", "Ir", "K", "Kr", "La", "Li", "Lr", "Lu", "Lv", "Mc", "Md", "Mg",
+  "Mn", "Mo", "Mt", "N", "Na", "Nb", "Nd", "Ne", "Nh", "Ni", "No", "Np",
+  "O", "Og", "Os", "P", "Pa", "Pb", "Pd", "Pm", "Po", "Pr", "Pt", "Pu",
+  "Ra", "Rb", "Re", "Rf", "Rg", "Rh", "Rn", "Ru", "S", "Sb", "Sc", "Se",
+  "Sg", "Si", "Sm", "Sn", "Sr", "Ta", "Tb", "Tc", "Te", "Th", "Ti", "Tl",
+  "Tm", "Ts", "U", "V", "W", "Xe", "Y", "Yb", "Zn", "Zr"
+  ]
+
+search :: Char -> [String] -> [String]
+search c = takeWhile start . dropWhile (not . start)
+  where
+    start [] = False
+    start (x:_) = toLower x == c'
+    c' = toLower c
+
+divide :: String -> [(String, String)]
+divide [] = []
+divide (x:xs) =
+  if null res
+    then [("?", xs)]
+    else res
+  where
+    res = go [] [] xs (search x elements)
+    go r _ _ [] = r
+    go r el rest candidates@(c:_) =
+      let el' = head c : el
+          candidates'@(c':_) = map tail candidates
+          r' =
+            if null c'
+              then (reverse el', rest) : r
+              else r
+       in case rest of
+            (y:ys) -> go r' el' ys (search y candidates')
+            _ -> r'
+
+advance :: ([String], String) -> [([String], String)]
+advance (els, rest) = map collect $ divide rest
+  where
+    collect (el, rest') = (el : els, rest')
+
+explode :: String -> [[String]]
+explode word = reverse . map (reverse . fst) $ go [([], word)]
+  where
+    go :: [([String], String)] -> [([String], String)]
+    go [] = []
+    go (x:xs) =
+      if null (snd x)
+        then x : go xs
+        else go (advance x) ++ go xs
+
+printFormula :: String -> IO ()
+printFormula word = do
+  putStr word
+  putStrLn ":"
+  mapM_ (putStrLn . (:) ' ' . unwords) . filter (not . null) $ explode word
+
+main :: IO ()
+main = getArgs >>= mapM_ printFormula
-- 
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