I'm currently taking Structure and Interpretation of computer programs from the University of Berkeley. Here is a nice question from one of the homeworks. You might want to try your hands at it.
Q6: Anonymous factorial
The recursive factorial function can be written as a single expression by using a conditional expression.
>>> fact = lambda n: 1 if n == 1 else mul(n, fact(sub(n, 1))) >>> fact(5) 120
However, this implementation relies on the fact (no pun intended) that fact has a name, to which we refer in the body of fact. To write a recursive function, we have always given it a name using a def or assignment statement so that we can refer to the function within its own body. In this question, your job is to define fact recursively without giving it a name!
Write an expression that computes n factorial using only call expressions, conditional expressions, and lambda expressions (no assignment or def statements). Note in particular that you are not allowed to use make_anonymous_factorial in your return expression. The sub and mul functions from the operator module are the only built-in functions required to solve this problem:
from operator import sub, mul def make_anonymous_factorial(): """Return the value of an expression that computes factorial. >>> make_anonymous_factorial()(5) 120 >>> from construct_check import check >>> check(HW_SOURCE_FILE, 'make_anonymous_factorial', ['Assign', 'AugAssign', 'FunctionDef', 'Recursion']) True """ return 'YOUR_EXPRESSION_HERE'