Some approximation theory routines in Haskell.
The Approx.Cheb module contains some basic Chebyshev routines (see Chebfun, ApproxFun.jl).
While not entirely full featured, it is sufficient to solve some linear ODEs.
The following solves d^2x/dx u = - sin (pi * x) with a sixth order Chebyshev polynomial approximation.
dl = DL (chebDf2 6) DirichletBC DirichletBC
u = dl <\\> Function (\x -> - sin (pi * x))