Convolving two functions doesn't work as expected in sage I'm trying to convolve two functions as follows: forget() x = PolynomialRing(QQ, 'x').gen() f1 = Piecewise([[(-1, 1), 1*x^0]]) f2 = Piecewise([[(0, 1), x], [(1, 2), -x + 2]]) g = f2.convolution(f1) Q = g.plot(rgbcolor=(1,1,0), figsize = 4); g I get that g is given by: > Piecewise defined function with 4 parts, [[(-1, 0), 1/2*x^2 + x +1/2], [(0, 1), -1/2*x^2 + 3*x], [(1, 2), -1/2*x^2 - x + 4], [(2, 3), 1/2*x^2 - 3*x + 9/2]]. Whereas, if computed manually, g is given by: > Piecewise defined function with 3 parts, [[(-1, 0), 0.5*x^2 + x + 0.5], [(0, 2), -0.5*x^2 + x + 0.5], [(2, 3), 0.5*x^2 - 3*x + 4.5] Why doesn't the one computed by sage match the correct function?

Does this bug ticket correctly diagnose your problem?

We are working on redoing piecewise functions, but in the meantime you are right that this bug is annoying.