unit_test_equals("sin[0] == 0", ... 0, ... divided_difference(@sin, 0)); unit_test_equals("sin[0, pi] == 0", ... 0, ... divided_difference(@sin, [0,pi])); unit_test_equals("sin[0, pi, 2*pi] == 0", ... 0, ... divided_difference(@sin, [0,pi,2*pi]));