From 8fa41c4e4c91723ff3e59f14fac8ed76685a9169 Mon Sep 17 00:00:00 2001
From: Dmitriy Pleshevskiy <dmitriy@ideascup.me>
Date: Wed, 20 Apr 2022 03:27:08 +0300
Subject: [PATCH] feat(haskell): add roman numerals decoder kata

---
 haskell/10_split_strings.hs          |  2 +-
 haskell/11_roman_numerals_decoder.hs | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 haskell/11_roman_numerals_decoder.hs

diff --git a/haskell/10_split_strings.hs b/haskell/10_split_strings.hs
index 4a69b2a..a1a50e2 100644
--- a/haskell/10_split_strings.hs
+++ b/haskell/10_split_strings.hs
@@ -1,4 +1,4 @@
-module Codewars.Kata.SplitStrings where
+module Codewars.Kata.SplitStrings (solution) where
 
 import qualified Data.Char as Char
 
diff --git a/haskell/11_roman_numerals_decoder.hs b/haskell/11_roman_numerals_decoder.hs
new file mode 100644
index 0000000..8fe6a2c
--- /dev/null
+++ b/haskell/11_roman_numerals_decoder.hs
@@ -0,0 +1,23 @@
+{-# LANGUAGE NumericUnderscores #-}
+module Roman (solution) where
+
+solution :: String -> Int
+solution = sum . mergeParts . map fromRoman
+
+mergeParts :: [Int] -> [Int]
+mergeParts [] = []
+mergeParts [n1] = [n1]
+mergeParts (n1:n2:rest)
+  | n1 < n2 = n2 - n1 : mergeParts rest
+  | otherwise = n1 : mergeParts (n2:rest)
+
+fromRoman :: Char -> Int
+fromRoman c = case c of
+  'I' -> 1
+  'V' -> 5
+  'X' -> 10
+  'L' -> 50
+  'C' -> 100
+  'D' -> 500
+  'M' -> 1_000
+  _   -> 0