"""Lecture 11: Non-local assignment examples."""

from ucb import interact, main, trace

def make_withdraw(balance):
    """Return a withdraw function that draws down balance with each call.
    
    >>> w = make_withdraw(100)
    >>> w(25)
    75
    >>> w(25)
    50
    >>> w(60)
    'Insufficient funds'
    """
    def withdraw(amount):
        nonlocal balance             # Declare the name "balance" nonlocal
        if amount > balance:
            return 'Insufficient funds'
        balance = balance - amount   # Re-bind the existing balance name
        return balance
    return withdraw


def make_withdraw_broken(balance):
    """Return a withdraw function that draws down balance with each call."""
    def withdraw(amount):
        # Removed the nonlocal statement
        if amount > balance:
            return 'Insufficient funds'
        balance = balance - amount   # Error!  There's no balance!
        return balance
    return withdraw


def make_withdraw_useless(balance):
    """Return a withdraw function that draws down balance with each call."""
    def withdraw(amount):
        # Removed the nonlocal statement
        b = balance          # Create a local binding
        if amount > b:
            return 'Insufficient funds'
        b = b - amount       # Re-bind the local binding
        return b
    return withdraw

 
@main
def run():
    interact()