praxis

commit 421a84350238990006031c627652518ea71f137d
parent cfa32faf70488b57623324ec3b07c2292ee5c295
Author: Jared Tobin <jared@jtobin.ca>
Date:   Thu,  5 Mar 2015 23:05:24 +1300

Add power exercise.

Diffstat:
A
20150303_power/Power.hs
 | 
23
+++++++++++++++++++++++

1 file changed, 23 insertions(+), 0 deletions(-)
diff --git a/20150303_power/Power.hs b/20150303_power/Power.hs
@@ -0,0 +1,23 @@
+
+module Power where
+
+import Data.Foldable
+import Data.Monoid
+
+powLinear :: Num c => Product c -> Int -> c
+powLinear a b = getProduct . fold $ replicate b a
+
+powLogarithmic :: (Num b, Integral a) => b -> a -> b
+powLogarithmic a b
+  | b <  0 = error "nonnegative powers only"
+  | b == 0 = 1
+  | even b =
+      let term = powLogarithmic a (b `quot` 2)
+      in  term * term
+  | otherwise =
+      let term = powLogarithmic a (pred b `quot` 2)
+      in  a * term * term
+
+powConstant :: Floating a => a -> a -> a
+powConstant a b = exp (log a * b)
+