# Tutorial 6: Functions
# Goal: Reuse code with func, parameters, return, and recursion.
#
# Define: func name(params) ... end. Call: name(args).
# A function without `return` returns `void`.

func greet(name)
    say("Hello, " + name + "!")
end

func add(a, b)
    return a + b
end

func is_even(n)
    if n % 2 == 0
        return true
    end
    return false
end

func factorial(n)
    if n <= 1
        return 1
    end
    return n * factorial(n - 1)
end

greet("Alex")
say("add(3, 4) = " + str(add(3, 4)))
say("is_even(10) = " + str(is_even(10)))
say("is_even(7) = " + str(is_even(7)))
say("factorial(5) = " + str(factorial(5)))

# Functions calling functions.
func square(x)
    return x * x
end

func sum_of_squares(a, b)
    return square(a) + square(b)
end

say("sum_of_squares(3, 4) = " + str(sum_of_squares(3, 4)))

# Challenge: write a function that counts down from n to 1.