function [y,yhat] = saw(x,M)  

% [0,1] periodic sawtooth with max at 0, min at 0.5
% Returns gridpoint values y and Fourier coeffs yhat at gridpoints x
% uniformly spaced over [0,1).

  y  = abs(2*x - 1) - 0.5;
  yhat = 2*mod(M,2)./(pi*M).^2;