% Point spread function used in the one-dimensional deconvolution example.
% The function differs from zero only in the interval [-a,a] with a
% positive constant a>0.The function is defined by the formula
%
% (x + a)^2*(x - a)^2;
%
% This routine does not involve any normalization of the point spread
% function.
%
% Arguments:
% x vector or matrix of evaluation points (real)
% a positive constant, should satisfy 0=1/2)
error('Parameter a should satisfy 0