diff --git a/.idea/dictionaries/orange.xml b/.idea/dictionaries/orange.xml
index 5bc621f..f7bad05 100644
--- a/.idea/dictionaries/orange.xml
+++ b/.idea/dictionaries/orange.xml
@@ -3,6 +3,7 @@
anki
matplotlib
+ memoize
\ No newline at end of file
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 6a2c036..cc49a16 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -2,11 +2,8 @@
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diff --git a/json_memoize.py b/json_memoize.py
new file mode 100644
index 0000000..5e31876
--- /dev/null
+++ b/json_memoize.py
@@ -0,0 +1,78 @@
+from __future__ import division, print_function
+
+from functools import update_wrapper, wraps
+import json
+import os
+
+
+def json_memoize(filename):
+ """Return a decorator that memoizes function calls in a JSON file."""
+
+ class JsonMemoize:
+
+ def __init__(self, fn):
+ self.fn = fn
+ update_wrapper(self, fn)
+
+ if not os.path.exists(filename):
+ with open(filename, "w") as f:
+ json.dump({}, f)
+
+ # XXX should work with **kwargs, too.
+ def __call__(self, *args):
+
+ with open(filename, "r") as f:
+ memo = json.load(f)
+ if repr(args) not in memo:
+ memo[repr(args)] = self.fn(*args)
+ with open(filename, "w") as f:
+ json.dump(memo, f)
+ return memo[repr(args)]
+
+ return JsonMemoize
+
+
+def timed(f):
+ """Return a timed version of function f.
+
+ The returned function returns a tuple of (time, real return value)
+
+ :param f: function to time
+ """
+
+ @wraps(f)
+ def wrapper(*args, **kwargs):
+ import time
+
+ time_start = time.time()
+ return_ = f(*args, **kwargs)
+ time_end = time.time()
+ time_delta = time_end - time_start
+ return time_delta, return_
+
+ return wrapper
+
+
+@json_memoize('json_memoize_tmp.json')
+def is_prime(n):
+ """Really inefficiently check if n is a prime number."""
+ if n == 0 or n == 1:
+ return False
+
+ for i in xrange(2, n):
+ if n % i == 0:
+ return False
+
+ return True
+
+
+assert (is_prime(0) is False)
+assert (is_prime(1) is False)
+assert (is_prime(2) is True)
+assert (is_prime(2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 10) is False)
+
+is_prime_timed = timed(is_prime)
+for c in range(1, 11):
+ time, result = is_prime_timed(86028157)
+ assert (result is True)
+ print("Call {}: {:.2f}s".format(c, time))