1 files changed, 21 insertions, 0 deletions
diff --git a/entries/funemy/symbolic/phib.py b/entries/funemy/symbolic/phib.py
new file mode 100644
index 0000000..c6fb23e
--- /dev/null
+++ b/entries/funemy/symbolic/phib.py
@@ -0,0 +1,21 @@
+from typing import List
+ 
+def phib(xs: List[int]) -> bool:
+    """
+    Instructions:
+        1. `pip install crosshair-tool`
+        2. modify the precondition `pre` to control the length of your fib sequence
+        3. run `crosshair check phib.py` in your terminal
+
+    pre: len(xs) >= 10
+    post: __return__ != True
+    """
+    if xs[0] != 0:
+        return False
+    if len(xs) > 1:
+        if xs[1] != 1:
+            return False
+        for i in range(2,len(xs)):
+            if xs[i] != xs[i-1] + xs[i-2]:
+                return False
+        return True