Hello Andrey,
Have you thought about using the ab>c to behave like in Mathcad (gives "true" if b is inside the interval (a,c))? I do not mind the way it is in SMath, but I know from my experience as a teacher that this is a standard mistake many students make.
Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"