From aeefdd269576bf3d3e97269cf5ed2b21584ab0ec Mon Sep 17 00:00:00 2001
From: Pal Kerecsenyi <pal@p.kerecs.com>
Date: Wed, 8 May 2024 10:51:04 +0100
Subject: [PATCH] Add sum digits

---
 sum_digits.hs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 sum_digits.hs

diff --git a/sum_digits.hs b/sum_digits.hs
new file mode 100644
index 0000000..443fd08
--- /dev/null
+++ b/sum_digits.hs
@@ -0,0 +1,15 @@
+import Data.Char (digitToInt, isDigit)
+
+sumDigitsRecur :: String -> Int
+sumDigitsRecur [] = 0
+sumDigitsRecur (x : xs) =
+  if isDigit x
+    then
+      digitToInt x + sumDigitsRecur xs
+    else sumDigitsRecur xs
+
+sumDigitsListComp :: String -> Int
+sumDigitsListComp i = sum [if isDigit x then digitToInt x else 0 | x <- i]
+
+sumDigitsMapFilterFold :: String -> Int
+sumDigitsMapFilterFold i = foldr (+) 0 (map digitToInt (filter isDigit i))