Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/breakfast-generator.py

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+# After being inspired by...
+# craftinginterpreters.com/representing-code.html
+# ...I'm implementing the breakfast generator that the author describes
+# therein.
+
+import random
+import string
+
+# Breakfast
+
+def breakfast():
+    fn = random.choice([
+        lambda: " ".join([protein(), "with", breakfast(), "on the side"]),
+        lambda: protein(),
+        lambda: bread(),
+    ])
+    return fn()
+
+def protein():
+    fn = random.choice([
+        lambda: " ".join([qualifier(), "crispy", "bacon"]),
+        lambda: "sausage",
+        lambda: " ".join([cooking_method(), "sausage"]),
+    ])
+    return fn()
+
+def qualifier():
+    fn = random.choice([
+        lambda: "really",
+        lambda: "super",
+        lambda: " ".join(["really", qualifier()]),
+    ])
+    return fn()
+
+def cooking_method():
+    return random.choice([
+        "scrambled",
+        "poached",
+        "fried",
+    ])
+
+def bread():
+    return random.choice([
+        "toast",
+        "biscuits",
+        "English muffin",
+    ])
+
+print(breakfast())
+
+# Expression Language
+
+# Because Python is a strictly evaluated language any functions that are
+# mutually recursive won't terminate and will overflow our stack. Therefore, any
+# non-terminals expressed in an alternative are wrapped in lambdas as thunks.
+
+def expression():
+    fn = random.choice([
+        lambda: literal(),
+        lambda: binary(),
+    ])
+    return fn()
+
+def literal():
+    return str(random.randint(0, 100))
+
+def binary():
+    return " ".join([expression(), operator(), expression()])
+
+def operator():
+    return random.choice(["+", "*"])
+
+print(expression())
+
+# Lox
+
+def lox_expression():
+    fn = random.choice([
+        lambda: lox_literal(),
+        lambda: lox_unary(),
+        lambda: lox_binary(),
+        lambda: lox_grouping(),
+    ])
+    return fn()
+
+def lox_literal():
+    fn = random.choice([
+        lambda: str(random.randint(0, 100)),
+        lambda: lox_string(),
+        lambda: random.choice(["true", "false"]),
+        lambda: "nil",
+    ])
+    return fn()
+
+def lox_string():
+    return "\"{}\"".format(
+        "".join(random.choice(string.ascii_lowercase)
+                for _ in range(random.randint(0, 25))))
+
+def lox_grouping():
+    return "(" + lox_expression() + ")"
+
+def lox_unary():
+    return random.choice(["-", "!"]) + lox_expression()
+
+def lox_binary():
+    return lox_expression() + lox_operator() + lox_expression()
+
+def lox_operator():
+    return random.choice(["==", "!=", "<", "<=", ">", ">=", "+", "-", "*", "/"])
+
+print(lox_expression())