function simple()
    local sum = 0

    # add 0 to 9
    for i in 10
        sum += i
    end

    sum == 45
end

function nests()

    local sum = 0

    # 5 times
    for i in 5
        # add 0 to 9
        for j in 10
            sum += j
        end
    end

    sum == 225
end

function break_loop()
    local sum = 0

    # 10 times
    for i in 10
        # add 0 to 9
        for j in 10
            sum += j
        end

        if i >= 4
            break
        end
    end

    sum == 225
end

function array()
    local sum = 0

    local values = [ 1, 3, 5, 7 ]

    for value in values
        sum += value
    end

    sum == 16
end

model TestModel
    a
    b
    c
end

function for_model()
    local test = TestModel(3, 4, 5)
    local key_combine = ""
    local sum = 0

    for key in test
        key_combine += key
        sum += test[key]
    end

    key_combine == "abc" and sum == 12
end