subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/scratch/facebook/stack.py

@@ -0,0 +1,25 @@
+class Stack(object):
+    def __init__(self):
+        self.items = []
+
+    def __repr__(self):
+        return self.items.__repr__()
+
+    def push(self, x):
+        self.items.append(x)
+
+    def pop(self):
+        if not self.items:
+            return None
+        return self.items.pop()
+
+    def peek(self):
+        if not self.items:
+            return None
+        return self.items[-1]
+
+def from_list(xs):
+    result = Stack()
+    for x in xs:
+        result.push(x)
+    return result