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Welcome to Functional Programming

Functional programming is a style (or "paradigm" if you're pretentious) where we compose functions instead of mutating state. By contrast, imperative programming updates state along the way:

car = create_car()
car.add_gas(10)
print(car.get_gas())
# 10

Functional programming composes functions that return new values:

car = create_car()
car_with_gas = add_gas(car, 10)
gas = get_gas(car_with_gas)
print(gas)
# 10

Each function's output becomes the next function's input. The original car isn't changed, because add_gas just returns a new copy.

Assignment

In this course, we're working on Doc2Doc, a command line tool for converting documents from one format to another (like Pandoc)... but there's a problem with the stylize_title function.

Before returning the document with the border, call center_title and pass it the document, capturing its return value in the centered_doc variable.