-function df = forward_euler(integer_order, h, f, x)
+function coefficients = forward_euler(integer_order, xs, x)
+ ##
+ ## Return the coefficients of u(x0), u(x1), ..., u(xn) as a vector.
+ ## Take for example a first order approximation, with,
+ ##
+ ## xs = [x0,x1,x2,x3,x4]
+ ##
+ ## f'(x1) ~= [f(x2)-f(x1)]/(x2-x1)
+ ##
+ ## This would return [0, -1/(x2-x1), 2/(x2-x1), 0, 0]. This aids the
+ ## solution of linear systems.