Sierpinski triangle: Difference between revisions

Content added Content deleted

Inline

@@ Line 3,216: / Line 3,216: @@
 and fold/reduce, wrapped as concatMap, can provide the list comprehensions too:
-<lang python>from functools import (reduce)
+<lang python>'''Sierpinski triangle'''
-from operator import (add)
+from functools import reduce
+from operator import add
 # sierpinski :: Int -> String
 def sierpinski(n):
+    '''Nth iteration of a Sierpinksi triangle.'''
     def go(xs, i):
         s = ' ' * (2 ** i)
@@ Line 3,232: / Line 3,235: @@
 # concatMap :: (a -> [b]) -> [a] -> [b]
 def concatMap(f):
+    '''A concatenated list or string over which a function f
+       has been mapped.
+       The list monad can be derived by using an (a -> [b])
+       function which wraps its output in a list (using an
+       empty list to represent computational failure).
+    '''
     return lambda xs: (
         reduce(add, map(f, xs), [])
@@ Line 3,238: / Line 3,247: @@
 print(sierpinski(4))</lang>
+{{Out}}
+<pre>               *
+              * *
+             *   *
+            * * * *
+           *       *
+          * *     * *
+         *   *   *   *
+        * * * * * * * *
+       *               *
+      * *             * *
+     *   *           *   *
+    * * * *         * * * *
+   *       *       *       *
+  * *     * *     * *     * *
+ *   *   *   *   *   *   *   *
+* * * * * * * * * * * * * * * *</pre>