assert_eq(sorted([42, 123, 3]), [3, 42, 123])
assert_eq(sorted(["wiz", "foo", "bar"]), ["bar", "foo", "wiz"])
assert_eq(sorted([42, 123, 3], reverse=True), [123, 42, 3])
assert_eq(sorted(["wiz", "foo", "bar"], reverse=True), ["wiz", "foo", "bar"])
assert_eq(sorted(list({"a": 1, "b": 2})), ['a', 'b'])
---

def f(x):
  return x[0]
pairs = [(4, 0), (3, 1), (4, 2), (2, 3), (3, 4), (1, 5), (2, 6), (3, 7)]

assert_eq(sorted(pairs, key=f),
         [(1, 5),
          (2, 3), (2, 6),
          (3, 1), (3, 4), (3, 7),
          (4, 0), (4, 2)])

---
assert_eq(sorted(["two", "three", "four"], key=len),
         ["two", "four", "three"])
assert_eq(sorted(["two", "three", "four"], key=len, reverse=True),
         ["three", "four", "two"])
assert_eq(sorted([[1, 5], [0, 10], [4]], key=max),
         [[4], [1, 5], [0, 10]])
assert_eq(sorted([[1, 5], [0, 10], [4]], key=min, reverse=True),
         [[4], [1, 5], [0, 10]])
assert_eq(sorted([[2, 6, 1], [5, 2, 1], [1, 4, 2]], key=sorted),
         [[1, 4, 2], [5, 2, 1], [2, 6, 1]])

---
sorted(1) ### type 'int' is not a collection
---
sorted([1, 2, None, 3]) ### Cannot compare NoneType with int
---
sorted([1, "one"]) ### Cannot compare string with int
---
sorted([1, 2, 3], key=1) ### "int" object is not callable