2016 Update

Task/Exponentiation-operator/Ela/exponentiation-operator-1.ela

@@ -0,0 +1,11 @@
+open number
+
+_ ^ 0           =  1
+x ^ n | n > 0   =  f x (n - 1) x
+      |else = fail "Negative exponent"
+  where f _ 0 y = y
+        f a d y = g a d
+          where g b i | even i  = g (b * b) (i `quot` 2)
+                      | else = f b (i - 1) (b * y)
+
+(12 ^ 4, 12 ** 4)

Task/Exponentiation-operator/Ela/exponentiation-operator-2.ela

@@ -0,0 +1,20 @@
+open number
+
+//Function quot from number module is defined only for
+//integral numbers. We can use this as an universal quot.
+uquot x y | x is Integral = x `quot` y
+          | else = x / y
+
+//Changing implementation by using generic numeric literals
+//(e.g. 2u) and elimitating all comparisons with 0.
+!x ^ n  | n ~= 0u = 1u
+        | n > 0u  =  f x (n - 1u) x
+        | else = fail "Negative exponent"
+  where f a d y
+          | d ~= 0u = y
+          | else = g a d
+          where g b i | even i  = g (b * b) (i `uquot` 2u)
+                      | else = f b (i - 1u) (b * y)
+
+
+(12 ^ 4, 12.34 ^ 4.04)

Task/Exponentiation-operator/Ela/exponentiation-operator-3.ela

@@ -0,0 +1,28 @@
+open number
+
+//A class that defines our overloadable function
+class Exponent a where
+  (^) a->a->_
+
+//Implementation for integers
+instance Exponent Int where
+  _ ^ 0           =  1
+  x ^ n | n > 0   =  f x (n - 1) x
+        |else = fail "Negative exponent"
+    where f _ 0 y = y
+          f a d y = g a d
+            where g b i | even i  = g (b * b) (i `quot` 2)
+                        | else = f b (i - 1) (b * y)
+
+//Implementation for floats
+instance Exponent Single where
+  x ^ n | n < 0.001 = 1
+        | n > 0 =  f x (n - 1) x
+        | else = fail "Negative exponent"
+    where f a d y
+            | d < 0.001 = y
+            | else = g a d
+            where g b i | even i  = g (b * b) (i / 2)
+                        | else = f b (i - 1) (b * y)
+
+(12 ^ 4, 12.34 ^ 4.04)