Boundary conditions in the resolution of a PDE with the FFT method

[accdd]

How to impose boundary conditions when solving a PDE with fft? For example here:
If I copy this code I get periodic boundary conditions. Thank you

 

[pasmith]

Well, yes. Discrete Fourier transforms are for periodic domains. If you have a non-periodic domain then depending on the boundary conditions you might be able to use a discrete sine or cosine transform, but in the general case you should use a discrete Chebyshev transform if you want access to an FFT based algorithm.