September 2017 Update

Task/Fibonacci-sequence/Python/fibonacci-sequence-10.py

@@ -1,10 +1,7 @@
-def fib():
-    """Yield fib[n+1] + fib[n]"""
-    yield 1  # have to start somewhere
-    lhs, rhs = fib(), fib()
-    yield next(lhs) # move lhs one iteration ahead
-    while True:
-        yield next(lhs)+next(rhs)
+def fib(n, c={0:1, 1:1}):
+    if n not in c:
+        x = n // 2
+        c[n] = fib(x-1) * fib(n-x-1) + fib(x) * fib(n - x)
+    return c[n]
 
-f=fib()
-print [next(f) for _ in range(9)]
+fib(10000000)  # calculating it takes a few seconds, printing it takes eons