Control Flow: Boolean Logic, Branching & Loop Invariants

Master multi-branch conditional ladders, truth tables, short-circuit evaluation, and while vs for loop termination proofs.

1. Boolean Algebra & Short-Circuiting

Conditionals evaluate truth expressions. In modern compilers, A && B stops evaluation if A is false (short-circuit), preventing null pointer dereferences.

1def safe_first_element(arr):
2    # Guard against None and empty list
3    if arr is not None and len(arr) > 0:
4        return arr[0]
5    return None
6 
7print(safe_first_element([10, 20, 30]))
8print(safe_first_element([]))