IFS in coconut (#727)

Author: Amaras

.gitignore

@@ -511,3 +511,6 @@ vscode/
 
 # Data file extension for Algorithm Archive
 *.dat
+
+# Coconut compilation files
+**/coconut/*.py

contents/IFS/IFS.md

@@ -134,6 +134,8 @@ Here, instead of tracking children of children, we track a single individual tha
 [import:5-12, lang:"python"](code/python/IFS.py)
 {% sample lang="c" %}
 [import:18-29, lang:"c"](code/c/IFS.c)
+{% sample lang="coco" %}
+[import:4-16, lang:"coconut"](code/coconut/IFS.coco)
 {% endmethod %}
 
 If we set the initial points to the on the equilateral triangle we saw before, we can see the Sierpinski triangle again after a few thousand iterations, as shown below:
@@ -203,6 +205,8 @@ In addition, we have written the chaos game code to take in a set of points so t
 [import, lang:"python"](code/python/IFS.py)
 {% sample lang="c" %}
 [import, lang:"c"](code/c/IFS.c)
+{%sample lang="coco" %}
+[import, lang:"coconut"](code/coconut/IFS.coco)
 {% endmethod %}
 
 ### Bibliography

contents/IFS/code/coconut/IFS.coco

@@ -0,0 +1,30 @@
+from math import sqrt
+from random import random, choice
+
+data point(x=0, y=0):
+    def __add__(self, other):
+        return point(self.x + other.x, self.y + other.y)
+
+    def __rmul__(self, other):
+        return point(self.x * other, self.y * other)
+
+def chaos_game(n, shape_points):
+    p = point(random(), random())
+
+    for _ in range(n):
+        p = (1/2) * (p + choice(shape_points))
+        yield p
+
+
+# This will generate a Sierpinski triangle with a chaos game of n points for an
+# initial triangle with three points on the vertices of an equilateral triangle:
+#     A = (0.0, 0.0)
+#     B = (0.5, sqrt(0.75))
+#     C = (1.0, 0.0)
+# It will output the file sierpinski.dat, which can be plotted after
+shape_points = [point(0.0, 0.0),
+                point(0.5, sqrt(0.75)),
+                point(1.0, 0.0)]
+with open("sierpinski.dat", "w") as f:
+    for p in chaos_game(10000, shape_points):
+        f.write("{0}\t{1}\n".format(p.x, p.y))