integrate(fun, min, max) = {
    // assume that min and max are integers.
    epsilon = 1
    l = max - min
    meanF(t) = fun(t)
    intervals = map(List.upTo(0, (l/epsilon)), ({|n| min + n*epsilon}))
    values = map(intervals, ({ |x | meanF(x)}))
    result = reduce(values, 0, ({|acc, x| acc + x})) * epsilon
    result
}

f(x) = x
integrate(f, 1, 100k)