Bad and Slow Numeric Integration in Haskell

It's not very fast, but at least it'll work on arbitrary real functions.

On the Length of a Differentiable Curve

So for a function f on an interval (a,b) the length of the curve produced is given by:

\int_a^b \sqrt{f'(x)^2+1} \, dx

You can try it using f(x)=x and get 2^(1/2) x, how thrilling.