diff --git a/2016-02-23/FunctionSyntax.hs b/2016-02-23/FunctionSyntax.hs
new file mode 100644
index 0000000..dda0b60
--- /dev/null
+++ b/2016-02-23/FunctionSyntax.hs
@@ -0,0 +1,30 @@
+module FunctionSyntax where
+
+sumTill :: Int -> Int
+sumTill 1 = 1
+sumTill n = n + sumTill (n - 1)
+
+sumTill' :: Int -> Int
+sumTill' n
+ | n == 1 = 1
+ | otherwise = n + sumTill' (n - 1)
+
+sumTill'' :: Int -> Int
+sumTill'' x = case x of
+ 1 | x > 0 -> 1
+ _ -> x + sumTill'' (x - 1)
+
+rot13Char :: Char -> Char
+rot13Char c
+ | isUpper = undefined
+ | isLower = undefined
+ | otherwise = error "ERROR"
+ where
+   isUpper = 'A' <= c && c <= 'Z'
+   isLower = 'a' <= c && c <= 'z'
+
+addOneSquare :: Int -> Int
+addOneSquare x =
+  let y = x + 1
+      z = y + x
+  in y * y + z