Just another update

Task/Factorial/Haskell/factorial-2.hs

@@ -1 +1 @@
-factorial n = foldl (*) 1 [1..n]
+factorial = product . enumFromTo 1

Task/Factorial/Haskell/factorial-3.hs

@@ -1 +1 @@
-factorials = scanl (*) 1 [1..]
+factorial n = foldl (*) 1 [1..n]

Task/Factorial/Haskell/factorial-4.hs

@@ -1,3 +1 @@
-factorial :: Integral -> Integral
-factorial 0 = 1
-factorial n = n * factorial (n-1)
+factorials = scanl (*) 1 [1..]

Task/Factorial/Haskell/factorial-5.hs

@@ -1,5 +1,3 @@
-fac n
-    | n >= 0    = go 1 n
-    | otherwise = error "Negative factorial!"
-        where go acc 0 = acc
-              go acc n = go (acc * n) (n - 1)
+factorial :: Integral -> Integral
+factorial 0 = 1
+factorial n = n * factorial (n-1)

Task/Factorial/Haskell/factorial-6.hs

@@ -0,0 +1,5 @@
+fac n
+    | n >= 0    = go 1 n
+    | otherwise = error "Negative factorial!"
+        where go acc 0 = acc
+              go acc n = go (acc * n) (n - 1)

Task/Factorial/Haskell/factorial-7.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE PostfixOperators #-}
+
+(!) 0 = 1
+(!) n = n * ((n-1)!)
+
+main = do
+  print (5!)
+  print ((4!)!)